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Samoa training report, capacity building in flood risk

1. th Simu abon Run Ratio Start States Save States ri Existing cordons 10 January 20 Bi Basin Model Vatar 1 Meteorologie Modet Gauge weights Figure 19 Component editor for simulation run Click the right mouse button when the mouse is on top of the Run 1 name in the Watershed Explorer and select the Compute option in the popup menu A window opens showing the progress of the run Close this window when the run finishes View model results Begin viewing the results by opening the basin model map Open the Vaisigano 1 basin model map by clicking on the name on the Watershed Explorer Components tab Select the Global Summary Table tool from the tool bar to view the summary results of the peak flows for all the elements In the basin model see Figure 20 Make a note of the computed peak discharge for the Junction element named Outlet View graphical and tabular results for the Junction element named Outlet Place the mouse over the Outlet icon in the basin model map and click the right mouse button Select the View Results Graph menu item see Figure 20 Select the View Results Summary Table menu item to view the subbasin element time series table see Figure 20 Select the View Results Time Series Table menu to view the subbasin time series table see Figure 21 13 F Global Sa amrurkarw Feguillg lor kun kun T ID F Proect Vemgeno Daai Rur Pun 4 mban oi hur Tani 100 Basin Modet Wiska 1
2. Figure 3 Flow hydrograph editor with data added Flow Hydrograph River Main River Reach Upper RS 1 9 Fiye m33 Figure 4 Plot of the flow hydrograph A Unsteady Flow Data 1in100 year flow Figure 5 Initial flow editor The first step is to put together a Plan The Plan defines which geometry and flow data are to be used as well as providing a title and short identifier for the run To establish a plan select New Plan from the File menu on the Unsteady Flow Analysis window First open the Unsteady Flow Analysis window by going to the Run menu and selecting Unsteady Flow Analysis Enter the plan title as 1 in 100 year unsteady flow and then press the OK button You will then be prompted to enter a short identifier Enter a title of lin100Unstdy in the Short ID box The next step is to fill in the Unsteady Flow Analysis Window as shown in Figure 6 Now press the Compute button and the model should run Fa Unstead y Flow Analysis Options Help Plan I m 100 Short ID lini00unsd Geometry File Geomeby with proposed bridge Unsteady Flow Fle Tint 00 year flow Programs to Run Plan Descqiption z Geomety Preprocessor w Unsteady Flow Simulation w Post Processor Simulation Time Window Starting Date 25Jul2006 Starting Time 0000 Ending Date 25 Jul2006 Ending Time fos Oo sesama ae 5 Minute gt Hydrograph Output Interval Detailed Output Intervat 5 Minute DSS Output F
3. Flow_hydrograph The entered data is shown in Figure 3 Push the Plot Data button and a flow hydrograph similar to that shown in Figure 4 should appear on the screen A downstream boundary also needs to be entered at River Station 1 1 For this example use the normal depth boundary condition Once you have selected the cell for the downstream end of the Main River press the Normal Depth button A pop up box will appear requesting you to enter an average energy slope at the downstream end of the river Enter a value of 0 0004 m m then press the Enter key This completes all the boundary condition data Press the OK button on the Boundary Conditions form to accept the data For the model to run in an unsteady mode it needs some initial conditions Now click on the Initial Conditions tab that is shown in Figure 1 A table will appear as shown in Figure 5 Add an initial flow of 130at River Station 1 9 and click the Apply Data button Now go to the File menu and select Save Unsteady Data As In the Title box add the title 1 in 100 year flow Flow Hydrograph C Read fen DSS before simulation awda Enter Table Data tine niewvat 15 Minute eo M Selact Enher the Data s Starting Time Aeference Fe Use Simulation Tine ee sai Tine Sto Adustment Dosons Cia bound conditions as edad E Nna ta adutments to computonsl ine se l Man Change in Fioni v cut changing time siant x EA pena OK Conceal
4. Ge vn wang _ Rating curves Fitting methods Least squares Weighted to high flow Discharge a HR Wallingford Rating curves Extension and fitting methods Use multiple equations Each has a defined range of stage Identify physically significant transitions Break point at bankfull stage Discontinuity at bankfull stage Analyse out of bank flow separately Page 18 A g a amp HR Wallingford Working with water iwa Rating curve extension Out of bank fitting Level _ Continuous Discontinuous Discharge Ge rn wang Uses of hydrometric Data Note this list is not exhaustive Catchment water resources planning Flood forecasting Flood discharge estimation Flow frequency analysis Model calibration Design of river works and flood defences Regulation and consenting a HR Wallingford Working with water av HR wa Rating curve exercise a HR Wating Exercise The following data has been measured using a flow meter in Samoa Discharge m s as lv 1 l 16 O a PT OoOo 30 O lJ GFZa O o 34 O el 32 O a P48 p45 14 16 20 27 30 32 34 37 40 43 45 50 65 a HR Wallingotd Exercise Plot the data on the graph paper provided Note plot the discharge Q on the x axis and the stage h y axis A curve of the following form has been fitted to the data Q 0 0168 h 0 0424 Where Q is the flow and h i
5. gt HR Wallingford Working with water Au vag Flow hydrograph data Flow Hydrograph lect D q d Pati f C Read from DSS before simulation Path Erter Table Data time intervat 1 Hour X Select Enter the Data s Starting Time Reference Use Simulation Time Date 03 03 1398 Time 0000 C Food Start Time Date Time _1 _ 08Ma1998 2400 7 09Ma1998 0600 Wale i emsa tell mtd ice haere Monitor this hydrograph for adjustments to computational time step Max Change in Flow without changing time step MnFbw Multiple Pot Data_ ok Camel a Hwa Three dimensional view BRIDI MOH ll Ji fy L yj PALL te HR Wallingford Working with water GY ve angers Modelling bridges Expansion Reach idealized flow transition pattern for 1 dimensional Bridge Culvert Data Beaver Cr Bridge P W a mmo u l SEE l _ a a Station f HR Wallingford Working with water a CB Looped networks Looped Geometry ceal Upper Spruce 9771407 a cian Storage areas ie a Ver Tost Fever a EA D a HR Walling esults flow and stage hydrographs a o OEE Fa sss lo Resh Kertant Rive Ste S99 8 Pile ree F Plot Stage 2 Plot Flow 2 Ote St
6. 80 0 79 0 78 0 77 0 76 0 75 0 Ill SEAT SENSES MANGAN AAP NA AA a RRS a N AYAK R N LRT SSE SSS SSS NY SSN SESAN SAN SNA SERS SIERENS NES EEE miw gt SSAA TAA I SEE RSS RW WWW a at A mAOD III 80 0 II II Elevation d Co VENETA SESS RENEE ARRAIA NE ANNESSA ERE OAN PRS SESS Rae aes Q 77 0 SEEDS MAA NANAY APANA CA N YN AY YAY PY TRESS TT w Pa QN SNNN PA T IVR SSS RSS RENN SSSR Ss 76 0 75 0 74 0 73 0 82 0 81 0 80 0 79 0 78 0 77 0 76 0 75 0 III I on stew crassana wasay SAAS ASSAD Ah WADE AAAS ESS RRR er wee F lk 0 5 10 15 20 25 30 Width m Plan and cross sections River Tanat at Llanyblodwel SS SRR ee l oad AKNAN as kS Ak SSSA N AYA Sack Sata SA a hes w taht pama A Laado mm sS SSS SSF SSS SS SANN NNNSNN S A Hii Pooch At 38 PH 5 12 5 line Hagen Pees TA m if i N Pa Bankfull hydraulic and geometric characteristics 15 12 86 Manning s n roughness coefficient Discharge Water surface slope 0 000298 1 336 Average cross sectional area 40 4 m Average flow width 26 7 m Average hydraulic radius 1 45 m Description of channel Bed is gravel and boulders Banks lined with mature alders ash and willow undergrowth of bramble nettle wild rose and
7. EU EDF 8 SOPAC Project Report 69d Reducing Vulnerability of Pacific ACP States SAMOA TRAINING REPORT CAPACITY BUILDING IN FLOOD RISK MANAGEMENT TRAINING IN FLOOD HYDROLOGY RIVER MODELLING AND FLOODPLAIN MAPPING 13t July 3 4 August 2006 Course participants setting uo the HEC HMS software AV r Walingiord Working with water EU EDF SOPAC Reducing Vulnerability of Pacific ACP States Samoa Capacity Building in Flood Risk Management Vaisigano River Apia 2 Prepared by Darren Lumbroso Ausetalia Titimaea Amataga Penaia and Michael Bonte Grapentin October 2008 PACIFIC ISLANDS APPLIED GEOSCIENCE COMMISSION c o SOPAC Secretariat Private Mail Bag GPO Suva FIJI ISLANDS http www sopac org Phone 679 338 1377 Fax 679 337 0040 www sopac org director sopac or IMPORTANT NOTICE This report has been produced with the financial assistance of the European Community however the views expressed herein must never be taken to reflect the official opinion of the European Community 1HR Wallingford Ltd Great Britain Meteorology Division Ministry of Natural Resources Environment and Meteorology Samoa 3Water Resource Division Ministry of Natural Resources Environment and Meteorology Samoa Pacific Islands Applied Geoscience Commission Fiji EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States Samoa Capacity Building in Flood Risk
8. Hydraulic modelling boundary conditions Upstream boundary condition is usually the flow hydrograph Downstream boundary is usually water level Approximate backwater length L in km can be estimated from L 0 7D s Where D is the depth of water in m and s is the slope of the river in m km 6 Vie Wallingford Working with water a HR Wallingford Errors Errors are mistaken calculations or measurements Effects can be quantified once corrected Random human factors Can be managed or eliminated by quality assurance and quality control procedures Sources of errors As Wallingford Hydro meteorology Faulty rain gauges Change in data collection method position datum Uncalibrated current meters Malfunction of gauging sites Human error in transcribing data Sources of errors Hydraulic modelling a HR Wallingford Survey errors closure benchmarks Gauge board datum Change in data collection method Human error in data entry into model Poor modelling procedure allingford Working with water Exercise Exercise Estimation of backwater length Calculate the backwater length for each of the following rivers in Fiji in the list below Nadrau Creek Waisali Creek Ba River Ba River Ba River Location Channel slope Bankfull Estimate of S depth D the backwater m km m length km L 0 7D s WaiWai Toge Karo Naval
9. Maintenance amp Operation av Working with water Na ee Training modules Day 1 Processes and definitions Precipitation Rating curves Flood flow estimation using statistical methods Rainfall runoff methods Ge rwng Training modules Day 2 Morning Introduction to HEC HMS modelling Afternoon Field visit to demonstrate flow gauging gt _ Training modules how do they fit ote together a Overall objective of Days 1 and 2 is to be able to estimate flood flows here HR Wallingford Working with water a a Training modules Day 3 Course to take place in one weeks time Concepts and principles in hydraulics Introduction to river modelling River resistance and roughness Floodplain mapping W Training modules R Wall Day 4 Course to take place in one weeks time River morphology Methods of flood defence Risk uncertainty and error Introduction to HEC RAS modelling g Training modules how do they fit together Vie Wallingford Working with water Na Wallingfo a Processes and definitions GY en wang Learning objectives To understand common process and definitions used in hydrological and hydraulic modelling a HR Wallingford Runoff Flow that enters the river system following precipitation rainfall A key area of study in hydrology Can be separated
10. Pakistan i a wo 3 lt Mada USA USA N Caledonia N Caledonia New Zealand 108 104 105 108 107 Catchment area A km2 The world s maximum floods Country Station Catchment Max discharge Year k area km m e USA Hawai Halawa 12 0 762 1965 5 49 USA Puerto Rico Las Piedras TE 816 1960 5 43 USA Nevada Nelson Landing El Dorado 56 5 2150 1974 573 Canyon USA Hawai Wailua Lihue 58 2470 1963 5 82 Cuba Buey San Miguel 73 2060 1963 5 62 French Polynesia Papenoo 78 2200 1983 5 65 Tahiti Mexico San Bartolo 81 3000 1976 5 86 USA Texas North Fork Hubbard Brook 102 2920 1976 5 77 New Caledonia Quateme Embouchure 143 4000 1975 5 85 USA Texas Mail Trail Creek Loma Alta 195 4800 1948 5 94 China Taiwan Cho Shui 259 7780 1979 6 22 New Caledonia Quateme Derniers Rapids 330 10400 1981 6 39 USA Texas Seco Creek d Hanis 368 6500 1935 5 98 New Caledonia Yate 435 5700 1981 5 81 Puerto Rico USA Central Cambalache 518 5520 1899 S73 USA Nebraska Little Nemaha Syracuse 549 6 370 1950 5 83 New Zealand Haast Roaring Billy 1 020 7 690 1979 SFT USA Texas Kickapoo Springs 1 040 16 000 1935 6 40 Iceland Skeidara at Bru 1 300 50 000 1996 7 34 Mexico Cithuatian Paso del Mojo 1 370 13 500 1959 6 16 Australia Pioneer at Pleystowe 379 9 840 1918 5 84 Japan Nyodo Ino 1 463 13 510 1963 6 11 Taiwan Hualien Bridge 1 506 11 900 1973 6 01 USA Texas W Nueces Bracketville 1 800 15 600 1935 6 20 India Macchu 1
11. Reach Upa s avresa s o a s 311 in 100 year Example 1 Steady flow Plan Existing 1807 2006 n xs 4 5 95 T Select All Cea Al eee 49 20 260 30 3 200 Station m o EESE gt Figure 12 Cross section plot and the selection of profiles Next plot a water surface profile Select Water Surface Profiles from the View menu bar on the HEC RAS main window From the Options menu on the cross section editor select the Profiles option Select the three available profiles This will bring up a water surface profiles for the 1 in 10 1 in 50 and 1 in 100 year floods for the Main River Next look at an X Y Z Perspective Plot of the river system From the View menu bar on the HEC RAS main menu select X Y Z Perspective Plots A multiple cross section perspective should appear on the screen Try rotating the perspective view in different directions Now look at the tabular output Go to the View menu bar on the HEC RAS main window There are two types of table available a detailed output table and a profile summary table Select Detailed Output Tables to get the first table to appear This table shows detailed hydraulic information at a single cross sections Now bring up the profile summary table This table shows a limited number of hydraulic variables for several cross sections There are several types of profile tables listed under the Std Tables menu bar of the profile table window Some of the
12. Shape Trapezoid Manning s n 0 05 Bottom width m 20 Side slope 5 Route upstream No Routing method Kinematic wave Length 3651 Slope 0 051 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 30 Side slope 5 Route upstream Yes Routing method Kinematic wave Length 3269 Slope 0 053 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 25 Side slope 5 Route upstream Yes Routing method Kinematic wave Length 1578 Slope 0 04 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 30 Side slope 5 Route upstream Yes Routing method Kinematic wave Length 2881 Slope 0 069 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m Side slope 5 Downstream Junction 3 Route upstream Yes Area 6 346 km Loss method Initial and constant Transform method Kinematic wave Baseflow method none Downstream Junction 3 Area 3 020 km Loss method Initial and constant Transform method Kinematic wave Baseflow method Recession Downstream Junction 5 Area 2 55 km Loss method Initial and constant Transform method Kinematic wave Baseflow method Recession Downstream Junction 6 Area 1 736 km Loss method Initial and constant Transform method Kinematic wave Baseflow method Recession Downstream Junction 7 Area 0 84 km Loss me
13. Bedelia 3 iiten2td1 100 Meteorclogc Modet Gaga weeighils Compe Tire TR JIH Coiro Sessilia Jan ang Volume Unde S Pd O 1000 mes Hyerologe Drainage Aroa Peak Depchue s Teo of Peak Figure 20 Viewing the global summary table Graph for Juretom athe Junction Element Outlet Results for Run Hun 1 Flow M33 4100 i 10 00 11 00 12 00 13 00 14 00 15 00 10Jan2001 Legd h B OUTLET Fg ibaik Aa H Gm Anih ka ARa 1 Barnaeq a Branch Paul kuriku Figure 21 Graph of outlet results 14 Simulate future urbanisation Consider how the Vasigano catchment would respond given the effects of future urbanisation The meteorologic and control specifications remain the same but a modified basin model must be created to reflect the anticipated changes to the catchment Create the modified basin model The urbanised basin model can be created by modifying a copy of the existing conditions basin model Place the pointer on the Vaisigano 1 basin model in the Watershed Explorer Component tab and click the right mouse button Select the Create Copy option Enter Vaisigano 2 as the basin model Name and Future conditions for the Description in the Copy Basin Model window Modify the new basin model to reflect possible future urbanisation Open the Component Editor for each of the three subbasins select the subbasin
14. Exercise Estimation of roughness Ge vn waning Information Eight photos of different rivers in the UK are attached For each river there is also a plan form cross section shapes details of slope discharge some cross section information and a short description of the channel Ge ve wang Based on the pictorial and section information given make an estimate of the roughness of each river reach Three steps Chow Tables find an n Use Cowan s approach determine an n Given the flow rate back calculate n and compare to answers 1 and 2 Ge unwangaq u Flow rates for part 3 River Severn Bewdley 358 0 m3 s Chatsworth 94 5 m3 s Drakelow 169 0 m s Avon 110 0 m s Moniflod 52 8 m3 s Tanat 54 8 m s Vyrnwy 167 7 m s Severn Montford 151 0 m s Plan Dowles 0 100 200 en a rd Cross sections Water level 5 1 88 LEE Terese 20 Len SSS SSIS TS REAR ee SRR NAONNANA RRS Da F r I I O Sosa RNEER RR T eee x Elevation mODN SSS See sss sss ss RE Le x SISO SS Bea AI SN SS SSS Sate AANA Sinais ZAN N won poor a an SERS Se RE Aa NAS SAN A AAS A WAN DA on Ratan oy Sey DNA Spe ae See CASS Ra NS SN SDA Sate gt LO RES SSS se SKS Se Se sss SRS soe ones SS S SSES SS SSS TAA Cartrencr ang belies hh SOK BAS EAST AN 22 E AA an AN ESN RRS ees Wiiiunnssuaam Ee AE 0 10 20 30 40 50 60 70 2 Width m PH 4 1
15. Vie Wallingford Working with water GY inven Uncertainty The components of uncertainty are e Natural variability e Knowledge uncertainty e Decision uncertainty Ge rwng Natural variability Climate and weather Storm surge and waves Vegetation growth Spatial variability Channel geometry Blockages of structures GP anger Characteristics of natural uncertainty Cannot be controlled New knowledge does not influence our ability to manage natural variability Historical information may indicate the possible range of natural variability s Vie Wallingford Working with water a HR Wallingford Internal to our assessment methods Can be reduced by improved knowledge data computer resource Bounds of some contributions can be assessed approximately AU He wenger Knowledge uncertainty process model uncertainty Process uncertainty e Processes considered and their representation Representation uncertainty Data uncertainties Parameter estimation Calculation methods Prang Knowledge uncertainty process model uncertainty Process uncertainty e Processes considered and their representation Representation uncertainty Data uncertainties Parameter estimation Calculation methods Vie Wallingford Working with water Ge vn waning sei Decision uncertainty How do the options behave as conditions move away from the central estimate Influence of uncertainty estimate
16. a HR Walinglord Hydraulic radius Represents the shape of the cross section Ratio of Area A to Wetted Perimeter P A Vie Wallingford Working with water GY in vind Putting things together Q Ks1 2 K A R 2 3 n R Q A5 3 s 1 2 n P2 3 Given a section shape we can calculate A and P With information on slope and roughness we can calculate discharge Page 16 GP rwng What is the roughness coefficient A number which describes the resistance of the channel to flow Depends upon the resistance equation being used We concentrate on Manning s equation due to its international use It has limitations e g varies with depth Page 17 a HR wanga What affects roughness x Bed surface material Channel irregularity Channel alignment and sinuosity Depth and discharge velocity Vegetation and sediments Altitude or gradient as surrogates for other parameters f Sinuosity Sinuosity S L S 5 i AA Sinuous River Corbis com AU vane Interaction between channel and floodplain NN E aii amp HR Wallingford Working with water i Evidence of flow interaction Classification of flows AE Flow states Sub critical e Slow and deep low kinetic energy Super critical e Fast and shallow high kinetic energy Critical e Special unique relation between velocity and mean depth y V gy HR
17. p E i a Usg Kas Kauge S I Cheed maere a Not Cro us CKA ap co hoy Gaara Orr ok n rou p Jol What areas of flood hydrology river modelling and flood risk management do you think should we concentrate on during the next training and practical sessions in October 2006 A Ze aul gu Sreef te ad ac hall tes owt ref pall t C lueh OK ee SS of aaa ufo Yu lt lt 7 f 3s lt f Spe mar ake prope LA Yr ore ove ECI LVA o i j f whe H KW ka a dL e pwd Laka EQS TAEI Bhrly V dod meg pre lx gt c La TS oP What other training in the fields of hydrology river modelling and water resources management would assist you in carrying out your work more effectively P i p a flow fore Cc eatin rad flor nak pran E aiii f TRAINING EVALUATION FORM Training in flood hydrology river hydraulics and flood mapping Was the general content of the training about what you had expected Ave _ No How do you think the training will help you carry out any work related to flood hydrology river modelling and flood risk management in the future uch more effectively Slightly more effectively _ The same as before Did you rate the speakers as Good Reasonable C Poor Were the presentations Too technical About right Not technical enough What was your overall assessment of the training Wy Excellent Good _ Reasonable Poor What was your assessment
18. Ba N amp gt PE TERETE R P Q NASER CASES ERRANS SSS NERS SAS ee NET Meret atte AAA Pata ate SN SSL ANS hee SESS ESAS TT NESNA SAANA SA OS Ht AARAS AERA ASA SEALS AEN SEY O SSNS AY NWN SSSSS SSS SEEN WSS SRS a A y SEERA SES Vu TREE ERA LA SSS SS SS RAV WSSSSSQWSSSSNSSSOS ANNT FATE x AE SAW SASS BS SOS AN aN ON ae SHANNEN VMN BAKATARANSASANS EE 0 10 20 30 40 45 Width m PH 7 12 95 f line Plan and cross sections River Manifold at llam River Manifold at llam Bankfull hydraulic and geometric characteristics 2 12 92 see Figure A3 6 Manning s n roughness coefficient 0 042 Discharge 52 8m s Water surface slope 0 001977 1 506 Average cross sectional area 35 6m Average flow width 21m Average hydraulic radius 1 64m Description of channel Bed material is gravel and boulders Bank vegetation of alder ash hazel beech sycamore and hawthorn traces with grass scattered undergrowth of bramble Flood plains of short grass pasture with hedgerows and wire fencing Plan Q Cross sections Water surface 15 12 86 80 0 79 0 78 0 77 0 76 0 75 0 74 0 SENN WSN SASt ANNARA NA SENECA F AARNA AARAA Wa SSS CAA YA o ROO BOAT SSA SSRESEEREN eek Sn aY Y hs hs umasa ss IST SSO J mill T D Pa ZZ ee G
19. Data requ i rements Maps Topography River channels Flood plains Embankments Structure details and channel section Photographs roughness estimates etc Page 33 y Working with water Zaa a Data requirements continued Boundary conditions for Inflows Downstream water levels Rating curves Calibration data including Flows within the model area Water levels at key sites Flood outlines for maximum extent Ne Modelling spacing Slope 1 in Section Spacing m 300 to 1 000 75 1 000 to 3 000 200 3 000 to 10 000 500 10 000 1000 Contributes less than 30 mm to overall uncertainty Typical one dimensional model layout HR Wallingford Working with water Typical one dimensional representation of the river Flood plain Flood plain Cross setlion lines Adjustment of conveyance calculation no embankments Flood plain Channel Flood plain embankments or high ground near river bank Channel Flood plain Flood plain Embankments Vie Wallingford Working with water a HR waning Use of calibrated model Match predicted and observed water levels flows Inbank and overbank separately Calibrate and verify on independent events Adjust coefficients Channel and flood plain roughness Structure discharge Uncertainties blockages bed movement etc HR Walingford Use of calibrated model Flood events of specified return p
20. Natural Channels US Geological Survey Water Supply Paper No 1849 pp214 Washington DC Hicks D M amp Mason P D 1998 Roughness Characteristics of New Zealand Rivers NIWA Christchurch 329pp Yen B C 1991 Channel Flow Resistance Centennial of Manning s Formula Water Resources Publications LLC Photographic advice Hicks amp Mason View of bottom cross section looking upstream a HR Wallingford Working with water Ge rn wang g Tabular advice in Chow 1959 TABLE 5 6 VALUES or TUE RouGuness COBFFICIENT n Boldface figures are values generally recommended in design Type of channel and deseription Minimum Normal Maximum A CLosep Conpuitrs FLowiNG Parriy FuLL A 1 Metal a Brass smooth 0 009 0 010 0 013 b Steel 1 Lockbar and welded 0 010 0 012 0 014 2 Riveted and spiral 0 013 0 016 O O17 APs A Cowans 1956 method Select a basic Manning s n value n Adjust basic value for effects of e shape and size of channel cross section n e obstructions n e vegetation n e surface irregularites n and e meandering of channel m Determine overall roughness value n from n m n n n n n Pirwan What about vegetation Vegetation increases the channel roughness Streaming A We can calculate increased roughness due to vegetation and determine the impact on the water level HR Wallingford Working with water uum What
21. Plot Cross Section option under the Plot menu on the Cross Section Data Editor The cross section should look the same as that shown in Figure 6 Enter all the other cross sections with River Stations number 1 8 to 1 9 in the same way Once all the cross sections have been entered save the data to a file before continuing Saving the data is done by selecting the Save Geometry Data As option from the File menu After selecting this option you will be prompted to enter a Title for the geometric data Enter Existing river geometry for this example then press the OK button see Figure 7 A file name is automatically assigned to the geometry data based on what you have entered for the file name Geometric Data Pile F 15 ee Tattle Tar z Hela Tools River Storage Sa Pomp RS R Junct D D Ceki save Geometry Data As Title Existing iver geomet Timpu nel ea facie a station Oo I HTab Param View j Picture Da OK Coa tem Ceser Seta z Select drive and path and enter new Tile a 0 7410 0 0875 Figure 7 Saving the Geometry Data The next step in developing the required data to perform steady flow water surface profile calculations is to enter the steady flow data To bring up the steady flow data editor select Steady Flow Data from the Edit menu on the HEC RAS main window A window should appear as shown in Figure 8 steady F low Data Ear Stenay tows ch
22. SOMES SS SRN SVN SES CANAS RT ACN SSS RS SSA SSSSSSS S R SANS MY h SSNS SSS SSS SA Bee SASS ES SSE RN AANA TEN WS SSS ee AAR Sa DLE RY S N ASS LRSM SSS TASSA S Sle aA ANA Ane SSS SN SSS a esa NA SSS SERRE N x e SANS m s See k E SSN Sa N NN ANN S OAA SS SEN 1 ese Scena be NY SN SSS s A w w Q ASS weta Sate SSN o SS SPM N NANN ANS RIG arte LAS xe ae F asas i a sasi a SOW z NIA NANNA SAND SWAN Nx SAASARNAY SERS SAR nas RNS SSE NOY SESE SANS so SRS I Bae ESSE 2 ROSS om m gt ite lt O Elevation mODN N yey A roe SAS AAS SANA CRC SANS Sy See ree AN A ay NESE SOARES ROLES SO N RONY VR cK SV SEN BNE SS N SS ms es NA SNS SS SASS N X NN SSS SEQ SSS SSN Oe N n k i ea Tan k N S SS SSS TaN SS SSS SSS SOO LSS NONA A GR lt S SSR SNS x See SS SSS Se cS PH 2 12 95 f line Plan and cross sections River Severn at Montford Bankfull hydraulic and geometric characteristics 12 11 87 Manning s n roughness coefficient Discharge Water surface slope 0 000186 1 5376 Average cross sectional area 139 m Average flow width 39 9 m Average hydraulic radius 3 31 m Description of channel Bed material unknown Left and right banks grass with
23. e a flow that varies with time The first step is to go to the Edit menu in the HEC RAS Main Window and select the Unsteady Flow Data Option The Unsteady Flow Data editor shown in Figure 1 should open 5 Unsteady Flow Data pae Ones a i Boundary Conditions initial Conditions Figure 1 Unsteady flow data editor For the Main River station labelled 1 9 select the Flow Hydrograph button shown in Figure 1 A new window should open as shown in Figure 2 Flow Hydrograph Arve Mia Aver Reach Upper AS 1 3 C Read hom OSS before simulation Select DSS file and Path oy sms i s ERE Eee eee Erte Table Data ina teva T Hou Select Enter the Data s Starting Time Reference z Use Simulation Tine Dae Time Fred Stat Tine Tine No Ordmales interpolate Missing Values Del Row aE Ins Row T Hudreorach L RS manjew eee nee 005 re Step Adiusiment Options Critica boundary conditions arko this hidrogiaph for ackuelments to carene ESRD Wax Change in Flow wilhout changing tine step a Min Flow o m Figure 2 Flow hydrograph editor In the Flow hydrograph editor select the following as shown in Figure 3 e Data time interval of 15 Minute e User Simulation Time Add a date of 25Jul2006 and a time of 00 00 e Addthe 1 in 100 year flow data that is in the Excel spreadsheet called HEC RAS Example_data xls in the Worksheet called
24. ee Aesch Meo Resch he Sitten ERD res wa coreto FED uray Ure yz og gn Fig Recorson dye wetan ERD res w Conetart Ei Servier ua Hy ogregh H rew wa Constant Sip aye Ua eure m 1200 14 00 10Jan2001 Pom RUN 1 esas OUTLET Fena Gate Pum an iener art beach Lt Pn rO rq i Unatable wih the gwen parameters WARMING Error in routing tor Reach 2 M T Pn rating tt uritiatie wth the green parameters MOTE 10186 Frihed Computing sena katan eur Mun 1 at tee Diu Exercise Use of HEC HMS to generate flood hydrographs Problem statement This example shows how to derive a flood hydrograph for the Vaisigano catchment using observed rainfall The Vaisigano catchment has a catchment area of 33 km There are three rain gauges in the Vaisigano catchment called Apia Vaisigano East and Upstream The objective of the exercise is to estimate the effect of proposed future urbanisation in the catchment on flood flows The catchment is shown in Figure 1 Upstream Figure 1 Schematic diagram of the Vaisigano catchment This example will require you to create a new project an entering gauge data A basin model using the initial constant loss Snyder unit hydrograph and recession baseflow methods will be created from the parameters shown in the Tables below Table 1 Vaisigano east rain gauge Rainfall mm 10 Jan 2001 10 00 ae 10 Jan 2001 10 15 0 fan 20011033080 p10 Jan 200110 45 0 E a a Table
25. f Clay Common drainage tile Vitrified sewer Vitrified sewer with manholes Vitrified subdrain with open jnt g Brickwork Glazed Lined with cement mortar h Sanitary sewers coated with sewage slimes with bends and connections 1 Paved invert sewer smooth bottom J Rubble masonry Min 0 009 0 01 0 013 0 01 0 011 0 012 0 013 0 017 0 021 0 008 0 009 0 01 0 011 0 01 0 011 0 011 0 013 0 012 0 012 0 015 0 01 0 015 0 011 0 011 0 013 0 014 0 011 0 012 0 012 0 016 0 018 Norm 0 01 0 012 0 016 0 013 0 014 0 014 0 016 0 019 0 024 0 009 0 01 0 011 0 013 0 011 0 013 0 012 0 015 0 013 0 014 0 017 0 012 0 017 0 013 0 014 0 015 0 016 0 013 0 015 0 013 0 019 0 025 Max 0 013 0 014 0 017 0 014 0 016 0 015 0 017 0 021 0 03 0 01 0 013 0 013 0 015 0 013 0 014 0 014 0 017 0 014 0 016 0 02 0 014 0 02 0 017 0 017 0 017 0 018 0 015 0 017 0 016 0 02 0 03 B Lined or built up channels B 1 Metal a Smooth steel surface Unpainted Painted b Corrugated B 2 Nonmetal a Cement Neat surface Mortar b Wood Planed untreated Planed creosoted Unplaned Plank with battens Lined with roofing paper Concrete Trowel finish Float finish Finished with gravel on bottom Unfinished Gunite good section Gunite wavy section On good excavated rock On irregular excavated rock Concrete bottom float finished wit
26. input to the next Route that a hazard takes to reach Receptors A pathway must exist for a Hazard to be realised The maximum discharge occurring during a flood event past a given point on a river system The degree of exactness regardless of accuracy Relationship between water depth and discharge at a particular point on a river Receptor refers to the entity that may be harmed e g a person property habitat etc For example in the event of heavy rainfall the source flood water may propagate across the flood plain the pathway and inundate housing the receptor that may suffer material damage the harm or consequence The vulnerability of a receptor can be modified by increasing its resilience to flooding Mathematical analysis of applying straight line principles to an observed relationship Impedance of normal water flow defined as flow form frictional turbulent etc The expected mean time usually in years between the exceedence of a particular extreme threshold Return period is traditionally used to express the frequency of occurrence of an event although it is often misunderstood as being a probability of occurrence Risk is a function of probability exposure and vulnerability Often in practice exposure is incorporated in the assessment of consequences therefore risk can be considered as having two components the probability that an event will occur and the impact or consequence associated w
27. is the effect o vegetation Blockage to flow area flow restricted to part of section Increases the effective wetted perimeter US Soil Conservation Service Estimation of Manning s n Base value n Channel character Np Channels in earth 0 02 Channels in fine gravel 0 024 Channels cut into rock 0 025 Channels in coarse gravel 0 028 Addition n for streamwise variation Character of variations in size and shape of cross sections n Changes in size or shape occurring gradually 0 000 Large and small sections alternating occasionally or shape 0 005 changes causing occasional shifting of main flow from side to side Large and small sections alternating frequently or shape 0 010 to 0 015 changes causing frequent shifting of main flow from side to side Addition n for obstructions in the watercourse Character of obstructions n Negligible 0 000 Minor 0 010 to 0 015 Appreciable 0 020 to 0 030 Severe 0 040 to 0 060 Obstructions may include debris deposits exposed roots fallen trees boulders rocks etc In assessing their effect the following factors should be considered reduction in flow area at various depths angularity of the obstructions position and spacing of the obstructions Addition n for vegetation Low influence n 0 005 to 0 010 Dense growths of flexible turf grasses or weeds of which Bermuda grass and blue grass are examples where the average depth of flow is 2 to 3 times the height of vegetatio
28. item to open the J nitial Constant Loss global editor see Figure 9 Change the Snyder Transform values using the same process see Figure 10 and the Recession Baseflow values see Figure 11 Change the name of the three junction elements Click the right mouse button when the mouse is on top of the Junction 1 element name in the Watershed Explorer and select the Rename option in the popup menu Change the name to Outlet Change the name of Junction 2 to East Branch Enter the parameter data for each of the reach elements Open the Component Editor for Reach 1 Click the Route tab in the Component Editor and add the Reach 1 data Do the same for Reach 2 ee Subbasin Loss Trenskem Basefkew Options Bastin Haran Wakkiqjarra 4 Figure 8 Subbasin area YI Initial Constant Loss Waisipana 1 e os J Figure 9 Initial and constant loss global editor snyder ransinrmWaisiparna 1 Figure 10 Snyder transform global editor Recession Basellow Waisimana 1 a Thr 0 78 Ratiot 0 79 Ratio th Figure 11 Recession baseflow global editor Change the name of the three junction elements Click the right mouse button when the mouse is on top of the Junction 1 element name in the Watershed Explorer and select the Rename option in the popup menu Change the name to West Branch Change the name of the Junction 2 element to Outlet Open the Component Editor for Re
29. laha mubarro riel Outlet Cd Har Ls Led Ble Ter sisa j a OK Cancel Ee Hep Select set of bediga coellicaerts to Edi i i i Figure 7 Bridge Modelling Approach Editor There is no need to change the settings that are currently selected in the Bridge Modeling Approach Editor Details of the various methods used to model bridges are available in the HEC RAS model manuals The next step is to click on the HTAB Param button on the Bridge Modelling Approach Editor The window shown in Figure 8 should pop up Change the headwater maximum elevation to 80 as shown in Figure 8 FA Parameters for Hydraulic Property I x Number of pomis on free flow curve rT Number of submerged curves fao Mumber of pami on each submerged curves f0 Appi number of pants to all bidges and culverts Head water maxinun elevation ad Tal water maximum elevation Options Maximum Swell Head Optional Ez OK Cancel Figure 8 Parameters for Hydraulic Property Tables The final step in modelling the bridge is to enter the Ineffective Flow Areas up and downstream of the bridge The Ineffective Flow Area Areas are the areas that will contain water that is actually not being conveyed ineffective flow In this case the proposed bridge will be on an embankment and the effective flow area of the upstream and downstream cross sections labelled 1 6 and 1 51 will change Click on the Bridge Culvert button in the Geometry Dat
30. occasional small willow trees Flood plains of short grass pasture with hawthorn hedgerows and fences Vie A Working with water ae Wallingford g Floodplain mapping A Learning objectives To know the uses of flood maps To understand the limitations of certain types of flood maps a HR Walingford Skills acquired To be able to distinguish between different types of river models To know the data requirements to construct different types of flood maps a HR Wallingford Working with water Ge rn waning Floodplain mapping uses Development control Are proposed developments in the floodplain Flood warning Which areas need flood warnings Where is the greatest risk e g in terms of people being injured buildings being damaged Insurance What is insurance exposure maximum probable loss Uwais Issues related to flood maps Level of hazard e The return period of design flood e Extreme flood outline Flooding outside mapped flood limits Uncertainty Updating Active flow areas Storage areas HR Wallingfotd Vie Wallingford Working with water A vomeee Methods for producing flood maps Historical flood outlines Flood levels plus topographic survey e Direct flood levels e g historical data e Predicted flood levels e g modelling Ge unwanaq ur Historical flood outlines What was the return period Extrapolate to required return period
31. of the training material MeExcellent Good _ Reasonable Poor How did you find the training exercises Too challenging _ About right Too easy What were the strengths and weaknesses of the training Jr ZZ Fdyarced 0 ecaye e e Enengh Keleyant Zma en gt Loft of Exercises PPactical Werke L enderstaad Speake Meabye qe berue ta net oD enh Shot hy senetines Lf Soy becouse Pre priv londi Pen werent well GATE What areas of flood hydrology river modelling and flood risk management do you think should we concentrate on during the next training and practical sessions in October 2006 wa ee Pd A Aie T PLENE ar A LEL TA tie The fof froar es More effectvely l What other training in the fields of hydrology river modelling and water resources management would assist you in carrying out your work more effectively aa On Erne of he FEM f f Guidelines Shaft us hel ba or make Hirod Alori Ie yurta cene GIS Vasa nas on laksa Fi fehe zes Atse PIRI DE ff CC mapa T TRAINING EVALUATION FORM Training in flood hydrology river hydraulics and flood mapping Was the general content of the training about what you had expected Yes No How do you think the training will help you carry out any work related to flood hydrology river modelling and flood risk management in the future Much more effectively Slightly more effectively _ The same as b
32. rank grass Left flood plain is sown with crops right flood plain is short grass pasture Field boundaries delimited by hedgerows Plan Cross sections 67 0 Water surface level 14 2 88 a ANNANN RRR MALLE AUS LULL Tan OSO Ca NS Aya a x S s sss X S SSS SANG N sss oo SS SSN EX SFA oo o o x SEK QAN RSS Se S eeo 2923929259 see a a ADROO SHH SEQ 3 2555324 8 nanan isa 3Gsasaqhkassq SS Ry ce SS rate x Ree z ARN o o o s S u ASN NR NNA e REREN SNRA aaa i E EAS EEA PAO SITS SS SEAS Elevation m AOD Sak SARA ON s s ALA Pests Suh ew RSE RSPR PARIS s ss o u Re gt O u 7 Ass PH 3 12 95 f line Plan and cross section River Vyrnwy at Llanymynech Bankfull hydraulic and geometric characteristics 14 2 88 Manning s n roughness coefficient Discharge Water surface slope 0 000372 1 2688 Average cross sectional area 131 6 m Average flow width 46 4 m Average hydraulic radius 2 25 m Description of channel Bed material unknown Right bank grass covered with scattered mature alders Left bank lined with alder and willow Left flood plain sown with crops right flood plain is short grass pasture Plan Cross sections Water level 12 11 87 ES SCE ee ne INSS ss l MANANNAN SS SEES SS ie cet SS ate AS SN NOS LSS NS SSS SS AERO xx SN ss A Seis SFR SS SSY lt SN 5
33. sections that bound the bridge gt The data for the geometry of the proposed bridge now needs to be entered The bridge geometry is defined by the following The deck roadway Number of piers optional note the bridge we will be modelling has no piers Sloping Abutments optional Bridge modelling approach information First enter the Deck Roadway geometry Click on the Deck Roadway button in the Bridge Culvert Editor A window similar to that shown in Figure 5 should open although it will initially contain no data The data for the Deck Roadway of the bridge is in the Excel Spreadsheet called HEC_RAS_Example_data xls in the Worksheet entitled Bridge Data Once you have entered all the data your Deck Roadway editor should appear as in Figure 6 Deck Roacway Data Editor 0 95 Min Wei Flow Et rasa a chard or eae Copy US lo OS Figure 5 Deck Roadway Data Editor The Distance you have entered in the Deck Roadway editor is the distance between the upstream side of the bridge deck and the cross section immediately upstream of the bridge The Width field is used to enter the width of the bridge deck along the stream The Weir Coefficient is the coefficient that will be used for weir flow over the bridge deck in the standard weir equation The Upstream Stationing High Chord and Low Chord define the geometry of the bridge deck on the upstream side of the bridge The Downstream Stationing
34. should not be confused with overall resistance av Ha wanes What is a roughness coefficient Historically this typically represents a resistance coefficient e A number which describes the resistance of the channel to flow e Depends upon the resistance equation being used e g Chezy Manning Colebrook White e It varies with depth of flow a HR Wallingford Working with water a u Eli Variation of n with depth Source Chow 1959 GU He vanng er Calculating roughness 1 Measurement of channel section discharge water level slope and use Manning s equation Photographic method Tabular method giving a range of values for different situations Cowan s or Soil Conservation Service method Experience Yuswan 3 Use Manning equation ARBs n AR 3 2 n Q Flow m3 s Cross sectional area m Hydraulic radius A P m m Wetted perimeter m Water surface slope m m Manning s roughness coefficient _ HR Wallingford Working with water uswa Other available equations Chezy equation 1768 resistance represented by Chezy s C V CN Rs Colebrook White equation 1937 resistance represented by Darcy f friction factor Eee k b Jr aR Re Jf av wass S Photographic method Available texts e Chow V T 1959 Open Channel Hydraulics McGraw Hill Book Company US Barnes H H 1967 Roughness Characteristics of
35. tidal range of about 1 0 m at the town The main cause of flooding at the town is from fluvial floods Flow data are as follows Estimated design flood flow 1 in 100 years flow 600 m s Flood event in 2003 720 m s Flood event in 2001 270 m s The following maps are attached Figure 1 Map of Ba River catchment Figure 2 Map of Ba town Figure 1 Map of the Ba River catchment development Historical flood extent Figure 2 Map of Ba town Case 2 Barrage on the River Sarawak at Kuching in Malaysia A new barrage is proposed for the River Sarawak about 2 km downstream of the city of Kuching in Malaysia in order to remove tidal effects from the river In the centre of the city The project is part of an urban regeneration programme A study is needed to assess the impact of the proposed barrage on flooding in the city and optimise the hydraulic design The site is about 5 km from the sea where the tide range is 5 metres The existing tidal limit is upstream is 20 km upstream from the mouth of the River Sarawak The design flood flow for the barrage is about 2490 m s This has a return period of 1 in 200 years There is one calibration point for the largest recent flood that occurred in 1987 and had a flow of about 1590 m s Better data exists for observed floods with flows up to 1100 m s The following drawings and photographs are attached Figure 3 General location map for the River Sarawak Figure 4 Photograph of
36. 00 10 00 11 00 11 00 11 15 11 15 12 30 12 30 13 30 13 30 16 30 Monday 24 July 2006 9 00 9 15 9 15 9 45 9 45 10 30 10 30 11 00 11 00 11 15 11 15 12 30 12 30 13 30 13 30 14 00 14 00 14 30 14 30 15 00 15 00 15 15 15 15 16 15 16 15 16 30 Flood hydrology Introduction to the training Processes and definitions Precipitation and runoff Exercise Break Rating curves Exercise Lunch Flood flow estimation using statistical methods Exercises Break Rainfall runoff methods Exercise Overview of day Flood hydrology Introduction to the day Introduction to the HEC HMS modelling system Exercises using HEC HMS modelling system Break Exercises using HEC HMS modelling system Lunch Field visit with SOPAC and MNREM to demonstrate flow gauging in the River Vaisigano River at Alaoa East gauging station on the Vaisigano River River modelling and flood mapping Introduction to the day Concepts and principles in hydraulics Exercise Introduction to river modelling Break Exercises Lunch River resistance and roughness Exercise Floodplain mapping Break Exercises Overview of day EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States Tuesday 25 July 2006 Wednesday 26 July 2006 Thursday 27 July 2006 9 00 9 15 9 15 9 45 9 45 10 30 10 30 11 00 11 00 11 15 1
37. 00 370 000 1953 6 76 Francou J amp Rodier J 1967 Essai de classification des crues maximales observ es dans le monde Cahiers ORSTOM serie Hydrologie 1V 3 19 46 ORSTOM Bondy France XV Vie Wallingford Working with water Na Wallingfo a Rainfall runoff methods a HR Wallingford Learning objectives Understand why it is necessary to construct a hydrograph Understand the effects of different catchment characteristics on the hydrograph shape Understand the rainfall runoff process to derive hydrographs a HR Walingfor Skills acquired To be able to understand the various components of a flood hydrograph To be able to know what shape a hydrograph is likely to be based on the type of catchment V4 a HR Wallingford Working with water a mwasi Why construct a flood hydrograph Estimate timing of flood Calculate flood volume Estimating flood warning times Assessing the affect of land use change Assessing the effect of flood mitigation measures Ge vn wang Rainfall runoff method J Discharge Q m s Does this When shape and ml of flood hydrograph is to be determine Give you Or this this A A Technique for relating the runoff to the rainfall that caused it is the Unit Hydrograph Method HR Wallingford __tagtime Tue _ Hydrograph i Rainfall Falling limb Rising limb Peak flow Q Base flow Time ho
38. 040 0 045 0 048 0 050 0 070 0 100 0 040 0 050 Max 0 033 0 040 0 045 0 050 0 055 0 060 0 080 0 150 0 050 0 070 0 03 0 033 0 04 0 035 0 04 0 05 0 033 0 06 0 04 0 05 0 12 0 08 0 11 0 14 D 2 Flood plains Min Norm Max a Pasture no brush 1 Short grass 0 025 0 030 0 035 2 High grass 0 030 0 035 0 050 b Cultivated areas 1 No crop 0 020 0 030 0 040 2 Mature row crop 0 025 0 035 0 045 3 Mature field crops 0 030 0 040 0 050 c Brush 1 Scattered brush heavy weeds 0 035 0 050 0 070 2 Light brush and trees in winter 0 035 0 050 0 060 3 Light brush and trees in summer 0 040 0 060 0 080 4 Medium to dense brush in winter 0 045 0 070 0 110 5 Medium to dense brush in 0 070 0 100 0 160 summer d Trees 1 Dense willows summer straight 0 110 0 150 0 200 2 Cleared land with tree stumps no 0 030 0 040 0 050 sprouts 3 Same as above but with heavy 0 050 0 060 0 080 growth of sprouts 4 Heavy stand of timber a few down 0 080 0 100 0 120 trees little undergrowth flood stage below branches 5 Same as above but with flood 0 100 0 120 0 160 stage reaching branches D 3 Major streams top width at flood stage gt 100 ft The n value is less than that for minor streams of similar description because banks offer less effective resistance Min Norm Max a Regular section with no boulders or 0 025 0 060 brush b Irregular and rough section 0 035 0 100 av HR Wallingford
39. 1 15 12 30 12 30 13 30 13 30 14 00 14 00 14 30 14 30 15 00 15 00 15 15 15 15 16 30 16 45 17 00 9 00 9 15 9 15 10 00 10 00 11 00 11 00 11 15 11 15 12 30 12 30 13 30 13 30 14 30 14 30 15 30 15 30 16 30 9 00 9 15 9 15 10 30 10 30 10 45 10 45 12 30 Samoa Capacity Building in Flood Risk Management Vaisigano River Apia 10 River modelling and flood mapping Introduction to the day River morphology Exercise Methods of flood defence Break Exercise Lunch Risk uncertainty and error Exercise Introduction to HEC RAS river modelling software Break Exercise using HEC RAS Overview of the day Use of HEC RAS modelling software Introduction to the day Exercise to develop a steady state HEC RAS river model Exercise to illustrate the hydraulic modelling of bridges Break Exercise to demonstrate unsteady flow modelling in the HEC RAS river modelling software Lunch Exercise to demonstrate how the deposition of sediment can be modelled using the HEC RAS river modelling software Exercise to show how weir structures can be modelled using the HEC RAS software Development of a HEC HMS hydrological model of the catchment to produce design hydrographs Combining HEC HMS and HEC RAS modelling software Introduction to the day Use of the design hydrographs from HEC HMS with HEC RAS to produce flood levels Break Exercise to test the knowled
40. 100 mm falls over the Vasigano catchment and the initial loss and infiltration losses are estimated to be 27 mm what is the effective rainfall a Hagai Exercise 2 The relationship between rainfall intensity mm hour duration D hours and return period 7 for Apia can be obtained by the equation Working with water a HR Wang Exercise 2 Plot a rainfall intensity duration frequency curve for the 1 in 100 year return period Use the graph paper and table provided Exercise 2 If the flow Q fora 5 km catchment can be estimated from the equation Q 0 005iA Where A is the catchment area and is the rainfall intensity If the runoff takes 0 5 hours to reach the catchment outlet calculate the 1 in 100 year flow Note use the 0 5 hour rainfall intensity estimate this from your graph Duration D Rainfall intensity hours i 110T D 1 mm hour Note T 100 1100 1000 900 O O O O O O cO N cO LO lt c anoy wiw Ajyisuazu jpesurey 200 100 5 0 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 Time hours 0 0 Vie Wallingford Working with water Na Wallingfo a Rating curves GY Hn wang Learning objectives Understand facto
41. 2 95 line Pian and cross sections River Severn at Bewdley Bankfull hydraulic and geometric characteristics 5 1 88 Manning s n roughness coefficient Discharge Water surface slope 0 000203 1 4926 Average cross sectional area 249 m Average flow width 78m information available for xs 1 and 2 Average hydraulic radius 3 24 m Description of channel Bed material gravel at upstream end otherwise unknown Banks grass with scattered willow alder and hawthorn trees undergrowth of nettle and brambles Left and right flood plains are short grass pasture Plan One Arch fe ra eia Pe e Bridge Deets Ss D25228 Baran ese eo h x me Atari REA ore ppt eee pose ak WAARAMAS AAA ASAI we Steet DARSDA DA JAS SS 3 SS 102 RRS SESS RS SENS Bs Soa PORT SR EIR SERENA SN SESS SAA SQ SS ERNE SAYS 104 102 SA SSEEASAD EASELS REESE ss ASN amp SS ATA ASTD BOS SSS s Ra x ENESRA AAC SNSNEAN AN SERS na NN AY CASAS SAS SRN wae Sate eo ASAS NASSAR E ANANN NASAN ENAN WSS SSS 4 SRS SAYRE 8 Elevation mAOD 98 96 104 Nn 85 SANS Se NASS Plan and cross sections River Derwent at Chatsworth PH 8 12 95 fiine Bankfull hydraulic and geometric characteristics 24 3 89 Manning s n roughness coefficient D
42. 2 Subbasin initial and constant loss methods and Synder unit hydrograph mm mm hour area a pol E Table 3 Subbasin area and baseflow data Subbasin Parameters Baseflow parameters Area km etal flow Threshold Recession orem sam rano to ae Table 4 Routing criteria for reaches Method Parameters o aa B J A meteorologic model will have to be created for the precipitation data Thiessen polygon weights detailed In Table 5 will be used for the user gauge weithing precipitation method The total rainfall measured at Apia was 150 mm and at a climate station in the upstream part of the catchment a total rainfall of 250 mm was recorded The storm rainfall is to be distributed in time using the temporal pattern of incremental rainfall from the Vaisigano East gauge The Vaisigano East rainfall data will be entered manually Table 5 Precipitation rain gauge weights Subbasin Apia Vasigano Upstream East gauge ai Jooo _ 025 J075 l 2 0 10 0 70 0 20 3 J09 010 000 A simulation run will be carried out for the existing catchment conditions to determine the existing rainfall runoff response Finally future urbanisation of the catchment will be modelled and the results compared to the existing conditions Create a subdirectory Create a subdirectory on your computer called C Hmsproj using Windows Explorer Create the project Begin by starting HEC HMS and creating a new project Select
43. 200 Structure models 1 10 to 1 50 Good visual impact HR Wallingford Working with water Ni Physical vs computationa models Physical models Computational models Flow processes Accurately Empirical 1 D reproduced equations Data needs Intensive Less intensive Results Detailed Less detailed Model extent Small areas Large areas Presentation Visual impact Computer graphics Future use Cannot be stored Can be stored e Complementary use of models a HR Wallingford Choice of model Type of application Data availability Accuracy required Time available Nature of flow steady or unsteady a HR Waling Choice of model Each application has its own characteristics e Planning e g floodplain mapping catchment development e Design e g individual schemes e Forecasting Vie Wallingford Working with water GU 2 vg Choice of model planning Standard scenarios e g a future climate change situation Steady or unsteady May use design methodology to set scenario e g definition of large flood May use continuous simulation ae HR Walingford Choice of model design Often a prescribed methodology Models may be prescribed Often based on hypothetical events Continuous simulation a possible future approach swan Choice of model forecasting Discharge forecasting or level forecasting Real time application Continuous simulation Updating forecasts error correction Vie
44. 5 Roughness 0 15 Area 100 Routing steps 5 Length 3651 Slope 0 051 Roughness 0 15 Area 100 Routing steps 5 Length 3269 Slope 0 053 Roughness 0 15 Area 100 Routing steps 5 Length 1578 Slope 0 04 Roughness 0 15 Area 100 Routing steps 5 Length 2811 Slope 0 069 Roughness 0 055 Area 100 Routing steps 5 Length 878 Slope 0 044 Roughness 0 055 Area 100 Routing steps 5 Length 4590 Slope 0 039 Roughness 0 15 Area 100 Routing steps 5 Length 3650 Slope 0 028 Roughness 0 15 Area 100 Routing steps 5 Length 2770 Slope 0 02 Roughness 0 15 Area 100 Routing steps 5 Length 1600 Slope 0 086 Roughness 0 010 Area 100 Routing steps 5 Length 961 Slope 0 0007 Roughness 0 10 Area 100 Routing steps 5 Plane 2 Leave this empty Options Leave this empty Loss 1 Initial loss 10 mm Constant rate 2 mm hr Impervious 0 Initial loss 10 mm Constant rate 2 mm hr Impervious 0 Initial loss 10 mm Constant rate 2 mm hr Impervious 0 Initial loss 10 mm Constant rate 2 mm hr Impervious 0 Initial loss 10 mm Constant rate 2 mm hr Impervious 0 Initial loss 10 mm Constant rate 2 mm hr Impervious 10 Initial loss 10 mm Constant rate 2 mm hr Impervious 10 Initial loss 10 mm Constant rate 2 mm hr Impervious 2 Initial lo
45. 900 15 600 1979 6 06 Taiwan Tam Shui Taipei Bridge 2110 16 700 1963 6 20 Japan Shingu Oga 2 251 19 025 1959 6 29 USA Texas Pedernaies Johnson City 2 330 12 500 1952 5 87 Japan Yoshino lwazu 2 810 14 470 1974 5 84 N Korea Daeryong Gang 3 020 13 500 1975 5 83 Philippines Cagayan Echague Isabella 4 244 17 550 1959 5 98 USA Texas Nueces Uvalde 4 820 17 400 1935 5 87 Japan Tone Yattajima 5 150 16 900 1947 5 87 India Vsundhra at Kashinagar 7 820 16 790 1980 5 68 USA California Eel Scotia 8 060 21 300 1964 5 92 Pakistan Ravi at Jassar 10 000 19 244 1955 5 71 Madagascar Betsiboka 11 800 22 000 1927 5 78 North Korea Toedong Gang 12175 29 000 1967 6 06 Australia Clarence at Lilydale 16 690 18 300 1954 5 40 South Korea Han Koan 23 880 37 000 1925 6 05 Pakistan Chenab at Marala 28 000 31 130 1957 5 76 Pakistan Jhelum at Mangla 31 000 30 847 1992 5 70 India Indravathi at Pathaguddem 40 000 24 862 1990 5 44 China Hanjiang at Ankang 41 400 40 000 1583 5 87 Madagascar Mangoky at Banyan 50 000 38 000 1933 5 70 Nepal Sapta Kashi at Chatara Kothi 54 100 24 000 1980 5 04 India Tapi at Kathur 64 000 36 500 1970 5 50 India Narmada at Gurdeshwar 87 892 69 400 1970 6 21 India Pranhita at Tekra 108 780 47 000 1986 5 52 Australia Burdekin at Clare 129 660 40 400 1946 amp 17 India Godavari at Polaeshwaram 307 800 87 250 1907 5 78 China Chang Jiang at Yitchang 1 010 000 110 000 1870 5 20 Russia Lena at Kusur 2 430 000 189 000 1967 5 52 Brazil Amazon at Obidos 4 640 0
46. A connection link shows the elements are connected 5 Connect the other element icons using the same procedure used to connect Subbasin 1 downstream to Reach 1 Move the hydrologic elements as necessary to complete the network shown in Figure 7 Move an element by placing the mouse over the icon In the basin model map Release the left mouse button to place the icon The upper and lower ends of a reach element icon can be moved independently Hasin Model Vaisipano 1 E X _ subbasin 1 Subbasin 2 Reach 2 Reach 1 Subbasin 3 kd lt E Figure 7 Subbasin reach and junction elements in their correct position Enter the element data Enter the area for each subbasin element detailed in Table 3 shown in Figure 8 Select a subbasin element in the Watershed Explorer or the basin model map Then in the Component Editor select the Subbasin tab and enter the subbasin area Enter the basin area for all the subbasin elements One way of entering parameter data for a subbasin element is to click on each of these tabs and enter the required information Another way to enter parameter data is to use the global editors Global editors are the most efficient way to enter data for several subbasin and reach elements that use the same methods Subbasin area can also be entered using a global editor by selecting the Parameters Subbasin area menu item Select the Parameters Loss Initial and constant menu
47. AA u S OEY odojs asa us buluuel jauueyd sejnHbueyoy so1lnespAy Ul s l diSuiid UO BSID1BX9 10 JOOUSYION Vie A Working with water ae Wallingford g River modelling A Learning objectives To know the appropriate river model to use for various situations To understand modelling procedures To appreciate why calibration of models is important a HR Wallingford Skills acquired To be able to distinguish between different types of river models To know the data requirements to construct a river model Vie Wallingford Working with water a HR waning Types of models Hydrological Detailed river flow computational physical Additions to flow models sediment water quality AV sn suing Hydrological models Prediction of river flows rainfall runoff models statistical methods Catchment models combined rainfall runoff and flow routing continuous simulation a yaa pus Flow routing Discharge only with simple dynamics e g Muskingum Method 1934 Linearised methods in many models Cunge identified parameters identified with river process Variation of wave speed and attenuation rate with discharge VPM C method used for catchment modelling f HR Wallingford Working with water AP re vain Flow routing 1490 lt Observed hydrograph at Erwood x x X Observed discharge at Belmont sonal vP MC
48. Being able to respond Knowing how to respond a conan Post flood recovery Relief for those affected Reconstruction of damaged infrastructure Regeneration of the environment and productivity in the affected area Review of flood management to improve processes and policies 12 Exercise Flood defence a HR Waning General Information At the position shown in the catchment Figure 1 a reach of the river was straightened and widened for flood defence purposes A flood embankment was placed adjacent to the river on the left bank to protect property and on the right bank set back 100 m on the flood plain to protect farm land This work was undertaken twenty years previously Dredging has been undertaken twice within the 20 years The substrate of the river is gravel Tree and bush maintenance has been undertaken on the left bank and grass cutting on the right bank HR waning Figure 1 embankment a HR Wallingford Task 1 In view of the fact that the town was being developed the river was straightened widened and embankments raised What was the likely impact of a the development b the flood defences on the flooding locally upstream and downstream What are the likely environmental impacts of the flood management solution a HR Wallingford Task 2 Figure 2 shows the hydrograph before development widening and straightening Sketch the impact of the development and the flo
49. Catchment Consequence Conveyance Culverts Design flood Deterministic approach Discharge Emergent vegetation Empirical formulae Error Exceedence probabilities Extrapolation Flash flooding a HR Wallingford GLOSSARY OF TERMS Closeness to reality The flow carried by a river at its bankfull water level The area from which water runs off to a given river see catchment Adjustment of a model to reach an acceptable degree of accuracy The area of land draining to a specific location It includes the catchments of tributaries as well as the main river An impact such as economic social or environmental damage improvement that may result from a flood It can be expressed quantitatively e g monetary value by category e g High Medium Low or descriptively Measure of the discharge carrying capacity of a channel K m s at a given depth and slope Pipes to enable the flow of water between catchments where roads and railways traverse watersheds The flood adopted for the design of a structure e g culvert bridge flood wall Using observations to produce theories as opposed to probabilistic approaches which design theories then test using observations The rate of flow of water as measured in terms of volume per unit time for example cubic metres per second m s Plants growing above water but that are rooted below the surface or along the water edge Formulae derived from field
50. G SEP OCT NOY DEC month Mean annual rainfall is approximately 3000 mm U Ge irwan Rain gauge network The area of the rain gauge is very small compared to the areal extent of the storm To get a representative picture of a storm over a catchment the number of rain gauges should be as large as possible Factors to consider with respect to the density of the rain gauge network e Costs Topography e Accessibility a HR wanga Estimating areal precipitation Rain gauges represent only a point sampling of the areal distribution of a storm For hydrological analysis a knowledge of the rainfall over the whole catchment is need Methods that can be used include e Calculating the arithmetic mean Thiessen s polygons Isohyetal method Radar HR Wallingford Working with water av HR Walling Thiessen s polygons Rain gauge Ta SEE Catchment area Thiessen s polygons a HR Wangs Isohyetal method Rain gauge Catchment area Contour line of equal 100 ax precipitation isohyetal Radar rainfall Valid Oct 08 1400 GMT i Vie Wallingford Working with water AP ve waingoe Intensity duration frequency curves The intensity of a storm decreases with the increase in storm duration Further more a storm of any given duration will have a higher intensity if its return period ts large Rainfall intensity duration frequ
51. Good A Reasonable Poor Were the presentations Too technical 7 About right Not technical enough What was your overall assessment of the training J Excellent Good Reasonable Poor What was your assessment of the training material Excellent AGood _ Reasonable _ Poor How did you find the training exercises A Too challenging About right Too easy What were the stren Ste Onath wot k na Teat a bt Eaa Hime per A fo Wa ef Fan fe Mogt of ne Fanna mater als We re under stindalole but few untamiliac terms i f I Nymbo oT xC C S f whi ch Mprove A Some Vad KAye ue P Wea kn ESS lack of fald ac NV ty whit 1 Wig lt hel o Wer t Antes What areas of flood hydrology river modelling and flood risk management do you think should we concentrate on during the next training and practical sessions in October 2006 What other training in the fields of hydrology river modelling and water resources management would assist you in carrying out your work more effectively Yer Son G V yust WAA b know Qua tara ko HA 1 i 1 Softwares to a C Fudvie dg e ang AVE a V Sof id 5 9 P bhe TRAINING EVALUATION FORM Training in flood hydrology river hydraulics and flood mapping Was the general content of the training about what you had expected Yes No How do you think the training will help you carry out any work related to flood hydrology r
52. High Chord and Low Chord define the geometry of the bridge deck on the upstream side of the bridge For most bridges this will be the same as the upstream information Bridge Culvert Data Geometry with proposed AAA File View Options Help rive EC App Data Eu z River Sta 155 gt t Bounding S s 1 6 1 51 Distance between 30 mJ RSe1 55 Upstream Bitidge j Grund Bank Sta 200 250 300 350 Elevation im x RS 155 Dovmstream Bridge Elevation mp 200 250 300 350 Station m Select the iver for Bidge Culvert Editing ra aa Figure 6 Deck Roadway Data Editor once initial data entry has been completed The Bridge Modeling Approach editor is used to define how the bridge will be modelled and to enter any coefficients that are necessary To bring up the Bridge Modeling Approach editor press the Bridge Modeling Approach button on the Bridge Culvert Data Editor Once this button is pressed the editor will appear as shown in Figure 7 except yours will only have the default methods selected Bridge Modeling Approach Editor add Co Oelie Badge t s t Low Flow Methods Use Compute C E Energy Standard Step CT Momenhum Coel Diag Cd iz A M Yamet tiarA cek PieeShapek DJ WSPRAO Method Class Aan WSPRD Varshies Highest E rpg Piriya High Flow Methods r Eneng Oink Standard Stap Pressure ando wei urea edet Cd fA lank for
53. Management Vaisigano River Apia 3 TABLE OF CONTENTS ACKNOWLEDGEMENTS u uu uu cited entra aant eons nun eaaer netstat laa ela anaes 4 EXECUTIVE SUMMAP Yuyu muyun man 2 di anensnenlareeb adit alan hina acacia ond cennaiset aud aie 5 UIST OC TON y an u uuu na uD Sa a 2ppsppush N 6 2 COURSEPARTIGIPANT0 u uy masa paqt2aykashuSustasukaya N 6 P arlielpapniSu u u uuu unu susan SN tupu edad adele buatan au pass tsa 6 FICSOUNCE POLrSOrelu uu u eo yasaq eae ee heed e eaten ee semen 7 9 C TPBRAININGOIPPOGRPANMNMEQuZu uuu uuu a usa asa taa Males 7 4 GOW RRS MATERIAL oe u uu u 2 uum nuusan mms asar sukan susiana 7 5 FEEDBACK AND EVALUATION a candsteteocabactale Micaecbieresadieiwatades 7 o OVIL OCO L senner ane a EE E E EE E E E EE 8 7 CONCLUSION AND RECOMMENDATIONS a 8 APPENDICES A Detailed Training Programme ar ar r sarrsss sa 10 B Daily Schedule Or ACUVUE S iesise E aaa ai lives enkisiieeceicelendes 12 C Completed Training Evaluation Forms digital distribution only D Training Examination Questions digital distribution only E Training Slides digital distribution only F Exercises digital distribution only G Glossary of Terms digital distribution only EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States Samoa Capac
54. Need to fill gaps in flood outlines Use aerial and video photographs from recent floods Use of satellite images Account for changes since the flood occurred a HR Walinglord Direct flood levels Historical flood levels e include old flood marks e interpolate for required return period Assess flood depth above bank level Rating curve from surveyed cross sections Vie Wallingford Working with water GU eng Predicted flood levels Range of methods and accuracy Rating curve from surveyed cross sections including gauging sites Hydrology and hydraulics Simple river models e g typical section Computational river models a HR Wallingford Methods of map production Hand drawn outlines e suitable for small areas Cross section derived e quick e adequate if no ground model Ground model derived using a GIS e grid based e Triangular Irregular Network TIN based a HR wanga Cross section derived maps Use real locations in river model Generate outline at peak of flood Add background or export to drawing package In some software packages simple animation can be carried out f Wallingford Working with water Generate ground model Export results from hydraulic model Use GIS e g ArcView with 3D Analyst Ground modelling representation e Raster for simple floodplains e TIN essential for embanked rivers Output in ArcView ArcGIS AutoCAD etc als d iaje ule l
55. O XS Saw CekO wus _ No For SUNAN PWRUTWA OngewsK Gaakon oA OO OAA TRAINING EVALUATION FORM Training in flood hydrology river hydraulics and flood mapping Was the general content of the training about what you had expected J Yes C No How do you think the training will help you carry out any work related to flood hydrology river modelling and flood risk management in the future V Much more effectively J Slightly more effectively _ The same as before Did you rate the speakers as Good C Reasonable C Poor Were the presentations Too technical About right Not technical enough What was your overall assessment of the training Excellent Good m Reasonable Poor What was your assessment of the training material Excellent Good _ Reasonable _ Poor How did you find the training exercises Too challenging C About right Too easy What were the strengths and weaknesses of the training n a I gt lt le CAV encthe of The trawnire is te Cov c ew A7 ane domas p 4 r O H set hano ren Onta y uee LZ has IES Cu Cra e e 27 gt A P a ub sb i ZT ts RA cA rr c oe Ca YW KA L amt aw 2 Or Lp Ar FS AL LLL lt amp j P A Fas l LA l A G L f 4 l p r AINED w 1 EE fL 4 ge han me yo Z AL lt oo Cec N a ya gt I s eden a k _ c t ores yy COVA LAAMUL Rn gt F a A a 1 c w
56. ON Se SESS ANS SSS L SSSA SSS p MSs SR SE SORES N ENTS NE ET RC WORE SSN RENE ss ee aN Stic SS SSE SESS N SSS N sss SSS SRS SEES Soe See SSN Sg SS SS SH SSES SNS SSNs Say DA NOAA AS yent y NNS lt S KARANA ARAARA NANN Rs e SEK SSS SOS TS SSS Ske SS bap RNN WNN SSSR gt ESSE AS SS DRS N X SS KS NS SNH N SRA RS ARNS N NS we TS N NANNY SSSSSSS ENS SR SS Elevation mODN DN SASS ass s ss ANNS ERASE TRANS WENN a we R DR vv Sh Wg CUNCA SANA W u Pe RRR RA T N eet ey NNER at pean A LARS Meee ARRAN Re SSS ohh Cyaan sees amp SS SAN Se ete Rae SASS S x NE SEA O r f C SSS x 20 Width ret PH 4 12 95 f line Plan and cross sections River Avon at Evesham Bankfull hydraulic and geometric characteristics 30 1 86 Manning s n roughness coefficient Discharge Water surface slope 0 000234 1 4274 Average cross sectional area 147 9 m Average flow width 45 m Average hydraulic radius 3 11 m y 4 amp wer ae 28 4 gt gt ee r Se pEr ee ye f i o Ean J 1 t i D b E Gd HES K o lt 4 G a gt wt _ h EY y Elevation mAQD 2 8 134 132 p 132 132 130 129 Plan eee a sa on Eas 2 Q aaa pene ee Cross sections Water level 2 12 92 RANTS el a S mien Fare toe th M A ree a s 2 TS
57. RS R Im Project at a slope Figure 1 Fixed sediment elevation window Fl Unsteady Flow Analysis iv Unsteady Flow Simulation Z Post Processor i E Tr imme YS eee wawmuasasss r m s lems lee s m r s s one s Q sr s s cesses gn ome Starting Date 25Ju 2006 Starting Time 00 Ending Date ae Ending Time 05 00 Computation Settings Computation Interval 5 Minut Figure 2 Unsteady Flow Analysis Simulation Window Once the model has finished all of the computations successfully you can begin viewing the results Several output options are available from the View menu bar on the HEC RAS main window including Create section plots Profile plots General plots Rating curves X Y Z perspective plots Detailed tabular output at specific cross section cross section table Limited tabular output at many cross sections Let s start by looking at Stage and Flow hydrographs Go to the View menu and select Stage and Flow Hydrographs Investigate the shape of the various water level and flow hydrographs for the different cross sections When you have done this go to the View menu and select Water Surface Profiles Click on the black arrow and you will see an animation of how the water surface changes with time Next look at an X Y Z Perspective Plot of the river system From the View menu bar on the HEC RAS main menu select
58. Righ Bank TT Figure 3 Changing downstream reach lengths in cross section 1 6 The required Information for a bridge consists of the river reach and river station identifiers a short description of the bridge bridge abutments if they exist bridge piers if the bridge has piers and specifying the bridge modelling approach To add a bridge to the model do the following l The first step is to return to the Geometric Data Window and click on the Bridge Culvert button A window similar to that shown in Figure 4 should appear Bridge Culvert Data Existing river geometry 4 i x Fie view Options Help Five EGR _ App D Reach Upper River Sta 4 t Descnpton EER ESEE enn aa eee J Bounding S s Distance betveeerc rrt pet rl Deck oe No Data for Plot No Data for Plot HT ab Select the river for Bridge Culvest E ding Figure 4 Bridge Culvert Data window 2 Go to the Options menu and select Add a Bridge and or Culvert from the list An input box will appear prompting you to enter a river station identifier for the new bridge Add the station identifier 1 55 Remember the River Station tag or identifier defines where the bridge will be identified within a specific reach The river station tag does not have to be an actual river station of the bridge but it must be a numeric value The river station tag for the bridge should be numerically between the two cross
59. SS k l r A On ie a 4 t oS 2 1 C ms A per S C tm A A ER ki r da oe A J as What areas of flood hydrology river modelling and flood risk management do you think should we concentrate on during the next training and practical sessions in October 2006 I P a ae ean t What other training in the fields of hydrology river modelling and water resources management would assist you in carrying out your work more effectively TRAINING EVALUATION FORM Training in flood hydrology river hydraulics and flood mapping Was the general content of the training about what von had expected Yes Nu flow do vou think the training will help vou carry onl eny work related to food hydrology river modelling and flood risk management in the future Much more effeetivels Shehth more etlechvel he same as before a i h Did you rate the speakers es wrod Reasonable Poor I s C re Were fhe presentations loo technical About right Not lechnical enough OK ty Sarde s What was vour overall assessment of the training Excelent 5 Gond Reasonable Poor l A s het was vour assessment of the training matertal Excelen Good Reasonable Poor llan did vou find the Drai exercises foo challenging About right Too easy VA gt 5 asd g us thik a lor het were the streneths aad weaknesses of the ratitu Ovan H redtube MW CAA U all Oho laina ii n UEL sport
60. To appreciate how to develop a flood hydrograph using HEC HMS Working with water APs Background to HEC HMS HEC HMS Hydrologic Engineering Center s Hydrologic Modeling System Developed by the US Army Corps of Engineers over a number of years Latest version is 3 0 1 Available for free from the internet www hec usace army mil together with comprehensive manuals and references a Hawan What does HEC HMS do HEC HMS is designed to simulate the precipitation runoff processes of catchments known as watersheds in HEC HMS It is designed to be applicable to a wide range of geographical areas and also to solve a wide range of problems Piw Uses of HEC HMS Flood hydrology Water resources problems e g water availability Effects of urbanisation on catchments Flood forecasting Design of dam spillways Floodplain regulation HR Wallingford Working with water a HR Walingfr Components of HEC HMS models Basin model Meteorologic models provides input to the basin model Control specifications defines the time step and time period of a model run Input data e g rainfall data Pirwan Hydrologic elements of HEC HMS Subbasin used to represent the physical catchment Reach used to convey downstream Junction used to combine flow from different hydrologic elements AV reon Working with water a HR Wallingford H
61. Wallingford Working with water Choice of model a HR Wallingford steady or unsteady Gates Embankments Tides Storage important Timing important e g for different sub catchments Attenuation through the reach a HR Wallingford Attenuation is important in Long reaches Wide flat flood plains Rapidly changing hydrographs a HR waning River modelling procedure Need to formalise the use of models to avoid mistakes Generic description of the modelling process Check review and approve at key stages HR Wallingford Working with water iaswan Modelling procedure Building phase Project specification Enhancement Software selection gt Project specific software Model definition Model construction L Data Calibration parameters r S P as Model proving j gt lt Review of model proving Faz Jelling procec coe Predictive simulation phase Design event simulation Blockage risk assessment Repeat design event simulation Review results gt no Report documentation Map production gt Archiving a HR waning
62. Wallingford Working with water Mas i Alternative classification Froude number Fr _V g y 1 2 where V is velocity m s y is depth m g is acceleration due to gravity m s Fr lt 1 subcritical flow Fr 1 critical flow Fr gt 1 supercritical flow I Water Level Working with water HR Wallingford Interpreting flow profiles Fluvial zone Interaction zone Tidal river flood profiles Tidal zone Distance m a HR Wallingford Working with water a ee Fluvial zone Contours of equal water level Tide Level h Discharge Q Tidal zone Discharge Q a Hwa pp Transitional zone Contours of equal water level Discharge Q R Wallingford Working with water What have we learnt Simple principles of different flow states Definition and calculation of e Uniform flow e Conveyance e Flow resistance Typical water surface profiles for various conditions a Vie Wallingfor Working with water av HR wa Exercise Principles in hydraulics Ge rwng The geometry Rectangular channel for simplicity m J in D E 10 metres GY rvam The numbers Water flows in an open rectangular channel 10 m wide Consider depths between 0 5 m and 3 m in 0 5 m steps Manning s n 0 04 0 03 0 02 Slope 1 in 500 200 and 100 Calculate discharge vel
63. What is your experience of flood hydrology and hydraulic modelling a HR Walingford Course objectives x To provide an overview of flood hydrology and river hydraulics To discuss issues related to estimating flood levels To provide illustrations from real life from the South Pacific To allow participants time to practise using the material s Vie Wallingford Working with water a HR Wallingford Format of course Presentations Exercises Discussion Documentation Ge vn waning see Background to hydrology and hydraulics Definitions Hydrometric analysis Flood hydrology River flow processes Flow estimation Examples for practice GP anger Rivers in the rural and built environment Conveyance Channel roughness Morphology Calculating water levels Structures and flood defences More examples and discussion Flood mapping s Vie Wallingford Working with water ae HR Wallingford What will we learn gt Knowledge of hydrometric data Construct a rating curve from data Different methods of estimating flood hydrographs Develop knowledge of open channel flow principles a HR Wallingford What will we learn Morphological river processes Know how water levels are calculated from flows What affects water levels at low and high flows Methods for assessing flood risk a HR Walingord River management gt Hydraulics j Construction J I
64. X Y Z Perspective Plots A multiple cross section perspective should appear on the screen Try rotating the perspective view in different directions Now press the black arrow and you should see an animation of how the water surface changes with time Now look at the tabular output Go to the View menu bar on the HEC RAS main window There are two types of table available a detailed output table and a profile summary table Select Detailed Output Tables to get the first table to appear This table shows detailed hydraulic information at a single cross sections Now bring up the profile summary table This table shows a limited number of hydraulic variables for several cross sections There are several types of profile tables listed under the Std Tables menu bar of the profile table window Some of the tables are designed to provide specific information at hydraulic structures e g bridges and culverts while others provide generic information at all cross sections From the View menu select the Profile Summary Table option make sure you select the maximum water surface elevation Open a new Excel spreadsheet file From the File menu in the Profile Output Table window select the Copy to Clipboard Data and Headings option In the Excel spreadsheet you have opened select the paste options and save the spreadsheet as Example_4_results xls Compare the maximum water levels from Exercise 3 running with an unsteady flow with no sediment to those that
65. Y K He Crd Figure 7 Location plan for the city of Brechin and the proposed bypass channel Vie Wallingford Working with water Na Wallingfo a River resistance and roughness GY en wang Learning objectives To know why it is important to estimate river roughness and resistance To understand the effect of different bed materials vegetation types and other river characteristics on roughness a HR Wallingford Skills acquired To be able to estimate the roughness values for different types of rivers and floodplains using at least two different techniques w HR Wallingford Working with water a awasi Why river resistance Channel resistance is the opposing force to the pressure imbalance which effects fluid flow Quantifying resistance is essential in determining water levels Greater resistance results in lower velocities and higher water levels av HB hat comprises resistance Resistance arises from e Bed surface material a wansi What comprises resistance Resistance arises from e Channel irregularity amp HR Wallingford Working with water a HR Wang What comprises resistance gt Resistance arises from e Channel shape Altitude or gradient e Vegetation and sediments Uvas What is roughness Roughness is only one component of channel resistance It results from boundary friction Large scale feature It
66. a Nasolo Exercise on accuracy assessment The following results were obtained from modelling a five year flood on a river in New Zealand m above datum m above datum m oo ns O 00 5 e s o x 5 pa C ne o tw in C om C gt f o a wanana x m ama nm The flow was 205 m s and the downstream level at the end of the reach was 11 70 m above datum The length of the reach is 24 5 km and the bankfull depth of the channel is approximately 4 5 m The hydraulic model contained 105 cross sections and the flood plain data were obtained from contours plotted at 0 25 m vertical interval from an aerial survey What would be your assessment of the accuracy of the predicted 10 year and 100 year flood levels which correspond to 250 and 430 m s respectively For these flows the hydraulic mean depth area breadth under flood conditions 1s as follows River flood flow m s Hyrdraulic mean depth m Can you estimate the improvement In accuracy of the predictions over the situation with no calibration data av HR Wallingford Morphological river flow processes Ge irranga Learning objectives e Understand the basics of river morphology e Understand the key parameters that affect river morphology Ge vn wang Skills acquired e Be able to comment on the possible effects of flood defence measures on river morphology e To know the concept of stream power a HR Wallingford Introdu
67. a Editor if it is not open already At the top of the Bridge Culvert Data Editor see Figure 6 you will see the words Bounding X s and the River Stations 1 6 and 1 51 Click on the river station 1 6 a popup box similar to that shown in Figure 9 should open Ineffective Flew Areas Sled inefiectve ode lli Homa r Mubin Blocks Leli Righa Graton Eka aa 12724 Pemeri T Pemeri Ok Cancel Delete Clear Figure 9 Ineffective Flow Areas Editor Select Multiple Blocks a box similar to Figure 10 should open although yours will have no data in it Add the data for ineffective flow areas from the spreadsheet this is also shown in Figure 8 and click the Apply Data button Once you have done this do the same for cross section 1 51 Ineidicciinve Flow Areas Cee Dea ow Figure 10 Ineffective Flow Areas Editor for Multiple Blocks Finally go to the HTAB editor and change the Headwater Maximum Elevation to 81 Now close the Bridge Geometry Editor and go to the File menu in the Geometric Data Editor and go to Save Geometry Data As Enter Geometry with proposed bridge as the title Now that all the data has been entered we can calculate the steady water profiles To perform the simulations go to the HEC RAS main window and select Steady Flow Analysis from the Run menu The Steady Flow Analysis window should appear as shown in Figure 11 except yours will not have any plan titles yet The
68. a foe tha pactie Jani Figure 8 Steady Flow Data Editor The first piece of information to enter is the number of profiles to be calculated For Example 1 we are going to calculate 3 profiles Enter the number 3 in the Enter Edit Number of Profiles box as shown in Figure 9 The next step is to enter the flow data Flow data is entered from upstream to downstream for a reach At least one flow rate must be entered for each reach in the river system Once a flow value is entered at the upstream end of a reach it is assumed that the flow remains constant until another flow value is encountered within the reach Additional flow values can be entered at any cross section location within the reach In Example 1 we will model the 1 in 10 1 in 50 and 1 in 100 year flows These will be entered at cross section 1 9 enter these as 500 900 and 1600 m s respectively The profile labels will default to PF 1 PF 2 etc Change these by choosing the Edit Profile Names from the Options menu within the Steady Flow Data Editor Change the profile names to 1 in 10 year 1 in 50 year and 1 in 100 year as shown in Figure 9 to represent the statistical return period of each of the events being modelled Steady Flow Data 1 in 10 1 in 50 1 in Jes er flow File Options Hep Figure 9 Steady Flow Data Editor with flows entered and profile names changed The next step is to enter any required boundary conditions To e
69. able a detailed output table and a profile summary table Select Detailed Output Tables to get the first table to appear This table shows detailed hydraulic information at a single cross sections Now bring up the profile summary table This table shows a limited number of hydraulic variables for several cross sections There are several types of profile tables listed under the Std Tables menu bar of the profile table window Some of the tables are designed to provide specific information at hydraulic structures e g bridges and culverts while others provide generic information at all cross sections From the View menu select the Profile Summary Table option make sure you select the maximum water surface elevation Open a new Excel spreadsheet file From the File menu in the Profile Output Table window select the Copy to Clipboard Data and Headings option In the Excel spreadsheet you have opened select the paste options and save the spreadsheet as Example_3_results xls Compare the maximum water levels from Exercise 2 running with a steady flow to those that you get from Exercise 3 with an unsteady flow hydrograph What is the difference in maximum water levels directly upstream of the bridge for the 1 in 100 year flood between the unsteady and steady flow models You have now completed the third example Exercise4 Running an unsteady flow model with the proposed bridge in place and an increase in the bed level caused by siltation If t
70. ach 1 and Rreach 2 and enter the detail from Table 4 see Figure 12 ihe Reach Route Options Basin Maree Valsigereo 1 Elemen Hame Reach 1 Muskingum K CHR 2 Mute X ce Subreaches 1 1 Figure 12 Muskingum data for Reach 1 Create the Meteorologic model Begin creating the meteorologic model by selecting the Components Meteorologic Model Manager menu Click the New button in the Meteorologic Model Manager window In the Meteorologic Model Manager window enter Gauge weights for the Name and Thiessen weights 15 minute data for the Description Open the Component Editor for the meteorologic model by selecting the Watershed Explorer In the Component Editor make sure the selected Precipitation method is Gage Weights see Figure 13 Name Gauge weights A ET ISl JE Preciptation Gage Weights Evapotranspiration Nor STO Unit Systeme Metric Figure 13 Component Editor for Meteorologic model Subbasins need to be specified for this meteorologic model Click the Basins tab in the Component Editor for the Gauge weights meteorologic model Set the Include Subbasins to Yes for the Vaisigano 1 basin model see Figure 14 After this step all subbasins in the Vaisigano 1 basin model are added to the meteorologic model 2 Meteorology Modal Basis Options Figure 14 Include subbasins in Meteorologic model Use the following steps and Figure 15 to complete the Gauge weights mete
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72. ainfall runoff approach Net Rainfall X Unit Hydrograph Runoff Hydrograph a HR Walger Hydrograph computation 1 Construct unit hydrograph 2 Estimate percentage runoff 3 Calculate event rainfall 4 Distribute according to chosen profile 5 Convolute net rain and UH 6 Add baseflow p ai HR Wallingford Working with water a HR Wallingford Baseflow Baseflow represents the flow in the river prior to the event To estimate e From empirical equations e From flood event analysis records of rainfall and runoff GY sn sang Hydrograph computation 1 Construct unit hydrograph 2 Estimate percentage runoff 3 Calculate event rainfall 4 Distribute according to chosen profile 5 Convolute net rain and UH 6 Add baseflow GU ve waning Problem catchments Small lt 0 5 km Large gt 500 km2 Permeable catchments e g chalk Urbanised catchments Flat and low lying possibly with pumped drainage Diversions extensive channel works we HR Wallingford Working with water a HR waning HEC HMS HEC HMS is a hydrological modelling system that includes a variety of models to produce flood hydrographs User specified unit hydrograph Clark s unit hydrograph Soil Conservation Service unit hydrograph HEC HMS a x Ni s Summary of hydrology lectures allingford Working with water Vie Wallingford Working with wat
73. ally homogenous region to understand the relationship between the mean annual flood Quar and the flood with a return period T Q May be possible to use data from Fiji American Samoa and Samoa to produce a regional flood frequency curve for ungauged catchments in Samoa GU vn wang m Limitations of statistical methods The results of the statistical flood frequency analysis is dependent on the amount of data available The more data that is available the better The there is a high degree of uncertainty in extrapolating to high return periods with limited data B P Vie Wallingford Working with water Wesssougaam Probability of a flood occurring in the next T years The probability R of a flood with a return period of T years occurring in the next n years is given by the equation R 1 1 1 T Exercises HR Wallingford Working with water av HR wage Exercise Estimation of a 1 in 100 year flood flow Ge vn wenger The problem The following annual maximum flow data has been recorded at a flow gauging station draining a catchment with an area of 35 km2 in Samoa over the past 16 years Annual maximum flow 1990 1991 1993 1994 1994 1995 1995 1996 1996 199 1997 1998 1998 1999 1999 2000 2001 2002 2002 2003 2003 2004 2004 2005 GP revenge The problem The problem is to estimate the 1 in 100 year return period flood flow for the gauge using the two pieces of graph pa
74. alysis System Developed by the US Army Corps of Engineers over a number of years Latest version is 3 1 3 May 2005 Available for free from the internet www hec usace army mil together with comprehensive manuals and references in PDF format a HR Wann a HR wan 1 in 100 year floodplain The floodplain Cross sections Flood 100 Year Floodplain Floodway Flood gt Fringe Encroachment Flood Elevation When Confined Within Floodway Encroachme Surcharge Stream Channel Fringe Base Flood Elevation Base Flood Elevation Before Encroachment Vie Wallingford Working with water av HR WalingiSr What does HEC RAS do i HEC RAS is an integrated package of hydraulic analysis programs in which the user interacts with the system through the use of a Graphical User Interface The program can perform steady and unsteady flow water surface calculations In future it will include a sediment transport module a HW Uses of HEC RAS i To estimate flood levels To assess the design of flood mitigation measures e g flood storage bypass channels flood walls To assess the design of bridges and culverts Effects of urbanisation on water levels Floodplain regulation Dam breaches W a mwi HHEC RAS Input and output Input cross section geometry and flow rates Output flood water elevations Normal Water Surface Flood Wat
75. and hydraulic modelling in the South Pacific e Copies of the HEC HMS hydrological and HEC RAS river modelling software e Several copies of the HEC HMS and HEC RAS user and technical reference manuals together with their application guides A copy of the training notes and exercises that were given to the participants is provided in appendices E and F 5 FEEDBACK AND EVALUATION At the end of the formal training period an evaluation form was distributed to assess the effectiveness of the training from the perspective of the participants The training forms were filled in anonymously at a time when the course co ordinators were not present in the training room Copies of the completed training evaluation forms are included in Appendix C of this report A total of seven participants filled in the evaluation form All the participants indicated that the general content of the training was about what they had expected and rated the overall assessment of the training as excellent Of the participants who responded five stated that the training would allow them to undertake their work related to flood hydrology river modelling and flood risk management much more effectively in the future with one stating that it would allow them to undertake these duties slightly more effectively Many of the participants indicated that they had found the course and exercises challenging The general feedback was summed up well by one participant
76. ant In time Parties persons with a direct interest stake in an issue Rate of work required by a river to transport water and sediment Astronomic tide plus storm surge water levels Screens in front of structures where rubbish is collected for removal Flood with a return interval the length of time between floods exceeding given magnitude of T years A general concept that reflects our lack of sureness about someone or something ranging from just short of complete sureness to an almost complete lack of conviction about an outcome Deterministic technique for relating rainfall to runoff The response of a catchment to a unit depth usually 1 cm of effective rainfall in a unit time 4 July 2006
77. ari2001 End Time HHimm 11 15 Figure 5 Time Window data for the Vaisigano East gauge Enter the Vaisigano rainfall data from Table 1 into the Table tab under the Component Editor as shown in Figure 6 eT Ry Time Series Gaga Tine Window Tabie Graph Time do Yi Hmm Precip aion iia inc 10Jan200 10 00 1OJan2001 10 15 60 0 1Quan2008 10 30 60 0 1 Jan2001 1045 40 0 10Jan2001 11 00 40 0 Timna 14 15 20 0 Figure 6 Manual entry of the rainfall data A plot of this data can be viewed by clicking on the Graph tab Creating the basin model Begin by creating the basin model by selecting Components Basin Model Manager menu item Create a new basin model with a Name of Vaisigano 1 and a Description of Existing conditions Create the element network The Vaisigano catchment will be represented with three subbasins two routing reaches and two junctions Use the following steps and Figure 7 to create the element network 1 Add the three sub basin elements Select the subbasin icon on the tool bar Place the subbasin icons by clicking the left mouse in the Desktop window 2 Add the two reach elements 3 Add the two junction elements 4 Connect Subbasin 1 to Reach 1 Place the mouse over the subbasin icon and click the right mouse button Select the Connect Downstream menu item Place the mouse over the upstream end of the reach icon and click the left mouse button
78. atchment Run HEC RAS model for design flows Start flood mapping Continue flood mapping EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States Samoa Capacity Building in Flood Risk Management Vaisigano River Apia 12 APPENDIX C Completed Training Evaluation Forms Appendices C to G available only in digital format EU SOPAC Project Report 69d Lumbroso amp others Appendix C Completed training evaluation forms TRAINING EVALUATION FORM Training in flood hydrology river hydraulics and flood mapping Was the general content of the training about what you had expected LT Yes B No How do you think the training will help you carry out any work related to flood hydrology river modelling and flood risk management in the future Much more effectively B Slightly more effectively _ The same as before Did you rate the speakers as T Good Reasonable Poor Were the presentations _ Too technical About right C Not technical enough What was your overall assessment of the training 4 Excellent Good Reasonable Poor What was your assessment of the training material T excetlent 1 Good _ Reasonable Poor How did you find the training exercises Too challenging ET About right Too easy What were the strengths and weaknesses of the training pa stres ha o y pik eesti a Groen x av J Copy Yu La eS wet als eo QSQA u ued oyan J k
79. ation Gage window enter Vaisigano East forthe Name and Vaisigano East rain gauge for the Description Click the Create button to add the precipitation gauge to the project The Vasigano East precipitation gauge is added to the Precipitation Gages folder under the Time Series Data folder in the Watershed Explorer Click the plus sign next to the gauge name The Watershed Explorer expands to show all time windows for the precipitation gauge A default time window was added when the gauge was created Select the time window in the Watershed Explorer to show all the time windows for the precipitation gauge Select Manual Entry from the Data Source dropdown menu and a Time Interval of 15 minutes from the dropdown menu as shown in Figure 4 KS Teas Series Gage Hame Vaisigano East Des riptiorr Valsigario East rain paige fe Dala Source Marval Ertry E w Time Indervat 15 Winutes a E e nae Figure 4 Time sertes gauge for Vatsigano East rain gauge set up In the Watershed Explorer window double click on the Vaisigano Fast precipitation gauge In the Component Editor open the Time Window tab and change the Start Date and End Date to 10Jan2001 Change the Start Time to 10 00 and the End Time to 11 15 as shown in Figure 5 Time Series Gage Time Wirsiow Table Graph Hame Last Sit Dae ceamar toma Start Time HH mm 10 00 End Date GoM yy 10Jl
80. az Spelt el Rives dan eJ j _ Reload Date T 50 yess ee Reach Upper j Ame Sta xed t 3 1 iv 100 pear Example 1 Steady flow Plan Existing 1807 2006 ai rr ss e ng re S 10 10 wo 20 300 80 400 Station m Da Figure 13 Cross section plot and the selection of profiles Next plot a water surface profile Select Water Surface Profiles from the View menu bar on the HEC RAS main window From the Options menu on the cross section editor select the Profiles option Select the three available profiles This will bring up a water surface profiles for the 1 in 10 1 in 50 and 1 in 100 year floods for the Main River as shown in Figure 14 Profile Plot fe x Fis Options Help Reaches E t Profiles je Reload Data Example 1 Steady flaw Plan Existing 16 07 2006 i i wh 5 WS 1 in 100 year amp i WS Tin 10 year 2m crt 1i too yeer 704 Cra 1 in 10 year ead Ground x OO qO 2009 300 400 5000 Ban Channie Datarea r rf Figure 14 Profile plot for Main River Next plot a computed rating curve Select Rating Curves from the View menu on the HEC RAS main window A rating curve based on the computed water surface profiles will appear for the first cross section on the Main River as shown in Figure 15 You can look at the computed rating curve for any location by selecting the appropriate river reach and river station from the list boxes at the top o
81. be produced 7 CONCLUSION AND RECOMMENDATIONS There is a need for sustained capacity building over a minimum of a five year period within both the MNREM s Hydrology Unit and Meteorology Division This should take a number of forms from members of staff being funded to carry out relevant masters and bachelors degree studies to shorter more focused courses such as the one just delivered It was interesting to note that on the evaluation forms filled out by the participants on the completed course many wanted to focus on learning how to use the hydrological and hydraulic modelling software It is also important to note that before these tools can be used effectively a firm grasp of the theory that underlies them is required Therefore it is recommended that further training in basic hydrological and hydraulic concepts is undertaken before further training is given on the use of specific software tools EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States APPENDIX Samoa Capacity Building in Flood Risk Management Vaisigano River Apia 9 Detailed Training Programme Thursday 13 July 2006 9 00 9 30 9 30 10 00 10 00 10 30 10 30 11 00 11 00 11 15 11 15 11 45 11 45 12 30 12 30 13 30 13 30 14 00 14 00 15 00 15 00 15 15 15 15 15 45 15 45 16 45 16 45 17 00 Friday 14 July 2006 9 00 9 15 9 15 10
82. be closed by double clicking the left corner of the window At this time the Steady Flow Simulation window can also be closed Once the model has finished all of the computations successfully you can begin viewing the results Several output options are available from the View menu bar on the HEC RAS main window including Create section plots Profile plots General plots Rating curves X Y Z perspective plots Detailed tabular output at specific cross section cross section table Limited tabular output at many cross sections Let s start by plotting a cross section Select Cross Sections from the View menu bar on the HEC RAS main window This will automatically bring up a plot of the first cross section on the Main River number 1 9 see Figure 13 You can also step through the plots by using the up and down arrow buttons Several plotting features are available from the Options menu bar on the cross section plot window These options include zoom in zoom out selecting which plans profiles and variables to plot and control over lines symbols labels scaling and grid options From the Options menu on the cross section editor select the Profiles option Select the three available profiles as shown in Figure 13 Select different cross sections to plot and practise using some of the features available under the Options menu bar ea ee ee ee Cross Section eer s pieg T Oix Select Profiles i F D fa Paras P ied
83. bridges and culverts while others provide generic information at all cross sections From the View menu select the Profile Summary Table option A table similar to that shown in Figure 18 should appear Open a new Excel spreadsheet file From the File menu in the Profile Output Table window select the Copy to Clipboard Data and Headings option In the Excel spreadsheet you have opened select the paste options and save the spreadsheet as Example_1_results xls You have now completed the first example X Y Z Perspective Plot File Options Upstream AS 43 z 4 tele 7 J i Downelream RS ha gt Pe e _ Plan Existing 16 07 2006 Example 1 Steady flow 718 Bank Sta Figure 16 X Y Z perspective of the Main River Figure 17 Cross Section Output River Main Frer w Profile 11 aaa ns ft CHEE The energy loss war greater than 1 0 ft D 3 m between the curent and previous cross sea bation Thri may indicate the need lor additonal cross bechor Sa n Enter 1o move ta nest dovmnsteam siver staon oeston Detailed tabular output at a cross section Profile Output Table Standard Table 1 elclel elce Iz mo e rs hepa fe Upp m IU IT ju x k L EAE T Jelelel JA 1a Figure 18 Tabular output in summary table format Exercise2 Adding a bridge to the steady flow river model with a If the Example_1 project is not still o
84. c wave method Before you start the exercise read pages 64 to 67 of the HEC HMS technical manual to give you the background to this hydrological modelling method Now start the exercise The basic model has already been set up However you will have to enter the various parameters for each of the Subbasins These are detailed in the Tables 1 and 2 below Table 1 Subbasin details Subbasin number Collector Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subcollector Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Subreaches 5 Shape Trapezoid Plane 1 Length 3634 Slope 0 07 Roughness 0 15 Area 100 Routing steps 5 Length 4711 Slope 0 04
85. ckground with good math physics and computer skills Specific knowledge in flood hydrology and river hydraulics was missing In general the knowledge base in hydrology modelling and water resources management is currently relatively weak at a technical level Only Sala Sagato Meteorology had some university level education in hydrology and losefatu Eti and Masina Ngau Chun Water Resource have baseline training in hydrology and hydrometry Participants at the course are listed below Participants Mr Sala Sagato Principal Officer Weather Meteorology Division Mr losefa Aiolupotea Strategic Planning Officer PUMA Mr Tumau Peni Sustainable Development Officer PUMA Mr losefatu Eti Hydrology Officer Water Resources Division Ms Masina Ngau Chun Senior Scientific Officer Water Resources Division Ms Litea Biukoto SOPAC GIS Resource Person Ms Alena Lawedrau Moroca SOPAC Hydrology Resource Person Training Coordinator Mr Darren Lumbroso HR Wallingford UK Mr Michael Bonte Grapentin SOPAGC Fiji EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States Samoa Capacity Building in Flood Risk Management Vaisigano River Apia 7 3 TRAINING PROGRAMME The training was delivered in three different forms e formal lectures and exercises e data gathering and work on individual assignments and e joint development of hydrological and hydraulic model for Vaisigano River The forma
86. ction e Need to work with the river to reduce maintenance and capital costs e Need to understand the processes and links between processes so we can work with the river a HR Wallingford Introduction e Many phenomena are difficult to understand and some remain unexplained e Need to combine understanding from geological and physical sciences Ger wang Morphological principles e Overview of river morphology e Sediment transport e Emphasis on introductory and mainly descriptive concepts e Practical applications Ge unwangsq a River morphology e Is concerned with shape plan form pattern and form of rivers e Morphology depends on Water discharge Sediment discharge Sediment characteristics Bed and bank composition Other factors and changes with time Ge unwangaq un Time scales of change e Change can occur at a range of timescales short term weeks months to a few years medium term 10 to 100 of years long term 1000s or millions of years e Engineers are interested in a human scale short and medium term a HR Wallingford Stable channel Different rivers and different reaches of river have different a alignments b cross section shapes c bed and bank material d slopes and valley characteristics Stable channels Za Wallingfo a For equilibrium channels the channel width depth and slope depend upon the discharge and sediment characteristics Relationships given by Regim
87. d storage layouts on line Wet Dry Under dry weather flow conditions Control structure Wet Dry Under dry weather flow conditions Inlet control Channel control 10 Storage reservoirs Other considerations Large land requirement Often not viable for large rivers Environmentally acceptable Local amenity and recreation Nature conservation Land use of areas to be flooded e g agriculture Safety reservoir legislation Pumping Effective method of flood control for relatively small areas and volumes Widespread use in e areas with poor drainage e for local runoff impounded by flood banks e areas affected by mining subsidence Static head typically 3 to 6 metres Pumps may be diesel or electric Channel must have adequate flow and storage capacity i III 1 Wn a HM jib g x 1 ee ea a ie G g ay L o e EIR ENP i 4 i l gI eE qi l i l yt l 4 Metien aces Nfa ig A TM ey 4 i f 11 Ge ve wang Flood forecasting and warning e Fluvial and tidal systems have three components e Detection e Forecasting e Warning dissemination e Achieving response is crucial e Understand the needs of different parties public council police GY veg Flood warning e Messages coded for recipients civil protection services and general public e Effectiveness depends on several factors Having awareness of a warning Being available to respond
88. dow should appear as shown in Figure 12 except yours will not have any plan titles yet The first step is to put together a Plan The Plan defines which geometry and flow data are to be used as well as providing a title and short identifier for the run To establish a plan select New Plan from the File menu on the Steady Flow Analysis window Enter the plan title as Existing Conditions Run and then press the OK button You will then be prompted to enter a short identifier Enter a title of Existing in the Short ID box The next step is to select the desired flow regime for which the model will perform calculations For this example we will be performing Subcritical flow calculations Make sure that Subcritical is the selected flow regime Saving the plan information is done by selecting the Save Plan from the File menu of the Steady Flow Analysis window EI Steady Flow Analysis Fie Help Pian En Shuti F Geomety Fie Emitingiveageomety Draad Flo Fie z wanting co eos stoi Ente to compute water sulaa pahis Figure 12 Steady Flow Analysis Simulation Window Now that everything has been set the steady flow computations can be performed by pressing the Compute button at the bottom of the Steady Flow Analysis Simulation window Once the compute button has been pressed a separate window will appear showing you the progress of the computations Once the computations have been completed the computation window can
89. e sactan had te be samedi war shy Sarg the utca dnt Caiman The pauk each method laked w Corona On ica Gap The pogan sd w Pe oom sector shce mcart method to Ied c cs det Fiver Beare Coch Flesch Kanan RSSI Pe Maw he oes cton had t be extended wama shy dang te et cate The padok seat method isiad te Comemnge om oed Gem The popen od ty he oon tan enai mented w ied Gear s woe la Rau kau a Remi as G NE Peor u lt w allingford Working with water z Oxted Pe F Coe J APPENDIX F Exercises EU SOPAC Project Report 69d Lumbroso amp others Appendix F Exercises Exercise 1 Using HEC HMS to estimate flood flows for the Vaisigano The purpose of this exercise is to estimate flood flows for different design and historical storms using a HEC HMS hydrological model of the Vaisigano River catchment The Vaisigano has been modelled in HEC HMS by splitting it up into 12 different Subbasins as shown in Figure 1 2 Basin Model Vasigano Seles 3 Subbasin 3 s SUbDaSin S subbasin2 S7 l Subbasin 6 Subbasin 4 i Subbasin 1 oe gt muy Subbasin 7 see ye M Junetion 2 Sy Subbasin 8 ep Subbasin 5 Ka og Junction 3 dunction 4 2 Subbasin 9 fr junctions Subbasin 10 Junetion 6 y Subbasin 11 elertunction 7 Subbasin 12 unction 8 Figure 1 HEC HMS model of the Vaisigano River catchment Each of the Vaisigano River catchment Subbasins has been modelled using a kinemati
90. e Use of lined channels in urban areas e g concrete e May not be environmentally acceptable Developed area Control structure Relief channel aswansi Flood relief or bypass channel e Water returned to river below flood risk area e Requires clear route and suitable topography e Control structure at upstream end e g weir or sluice Embankment with control structure Developed area Flood storage area Embankment with control structure AU He wang Storage reservoirs e In many parts of the world it is common practice to attenuate runoff from new developments Storage reservoirs store excess flood water and limit flow passing downstream Control structures required Can cause increased flood risk downstream if incorrectly designed Issues of ownership operation and maintenance Ge rwng Impact on hydrograph Storage adequate A Pre flood storage Post flood storage v 50 lt O A O Ne Impact on hydrograph Filled storage A Pre flood storage Post flood storage Discharge Ae He wager r Storage reservoirs On line reservoir controls Orifice Flume Pipe Weir Notch Vertical gate Radial gate Tilting gate or weir Spillway for overflow energy dissipation needed Off line reservoir Usually has control on main channel Control on bank into storage area Provision to drain reservoir after storm lt a HRWatingrd Floo
91. e maximum flood Q fora catchment with an area A can be estimated from Q 500A Where A gt 90 km Q 100A Where A lt 90 km gt wae Vie Wallingford Working with water Usa am Flooding in Fiji REMEMBER the risk RESPECT the river BE ALERT BE PREPARED a Flood definitions Design flood The flood adopted for the design of a structure e g bridge culvert flood wall Probable maximum flood PMF The extreme flood that is physically possible as a result of the most severe combination of meteorological and hydrological factors GY en vaingerd Estimating flood flows Estimates of peak flood flows magnitude e g peak flow measured during a flood event often from a gauging station Prediction of timing shape and volume hydrograph 0 5 10 15 20 25 30 35 40 45 50 Time hours Page 12 AV HR Wann Working with water ydrology and flood flow estimation Hydrology Flow measurement e rainfall a HR Wallingford e evaporation e groundwater e runoff Hydrographs Statistical ydrograp methods e unit hydrograph e Various methods e Various methods Flood flow estimate av Hwa i STATISTICAL METHODS Avr wang Return period The return period T is the average interval in years between years containing a flood exceeding a given magnitude T
92. e not available and the simulation must be re run Use the Watershed Explorer to compare results from Run 1 and Run 2 Click the Results tab in the Watershed Explorer and select both simulation runs The Watershed Explorer expands to show all the hydrologic elements with results Then select the Outlet junction and watch the Watershed Explorer expand to show all the 15 Day 3 HR Wallingford Working with water rwn Introduction to the training Ne River modelling and flood mapping Why model rivers Why map floods lt y in samoa fib Sie FA ie Weis supposes ve N wer maipe B flow to the seg but we should get ri of ths profesa Fia and Boks CN 5 the samoa flonding dilemma tmey recognise it is C Segieveirsewos Se e Source Samoa uswa a mt 2001 flooding in Apia HR Wallingford Working with water av Rag Programme Concepts and principles of hydraulics River modelling River resistance and roughness River morphology Methods of flood defence Risk and uncertainty Use of HEC RAS modelling software Ultimate objectives 7 OE Re RS RS Hazard Flood map Risk Damage to infrastructure buildings harm to people Page 5 Vie Wallingford Working with water Na Wallingfo a Concepts and principles in hydraulics GY en wang Learning objectives Different principles of flow states Definition and calc
93. e theory a HR Wallingford Stable channels The channel forming discharge is called the dominant discharge which is frequently approximated by the bank full discharge Ge vn wang Channel plan form e Straight channels e Meandering channels common meanders move and may develop in time but system is dynamically stable e Braided channels system of channels which divide and rejoin and are dynamically stable Ge HR wage n Channel plan form a Straight channel reach CS b Meandering channel EN z as s SS c Braided channel reach GU vn waning se Channel plan form A meandering plan form is frequently characterised by the meander wave length amplitude and sinuosity These are related to the river discharge and sediment characteristics Na us Channel plan form Wavelength Amplitude Ge vs waning sei Channel plan form x In braided river systems the intensity of the braiding measured either by number of channels or length of river banks tends to be constant at a specific location but varies with the dominant discharge sediment characteristics and valley slope GU unwangaq us Channel plan form Relationship Between Valley Slope Sy and Equilibrium Water Surface Slope a Sy Spy b Sra gt Sy gt Spui c Sy Sra d Sy Sgs Ge vn wang Channel plan form meanders x Knowledge allows a assessment of stabil
94. efore Did you rate the speakers as L J Good Reasonable C Poor Were the presentations Too technical About right Not technical enough What was your overall assessment of the training LA Excellent Good Reasonable Poor What was your assessment of the training material Excellent 4 Good _ Reasonable Poor How did you find the training exercises L Too challenging About right C Too easy ths and weaknesses of the training S G paula p maly alla sy 3 n Ads aba Jood wo Aull ing Ole 4 Su A was Wn ke sty ar used What areas of flood hydrology river modelling and flood risk management do you think should we concentrate on during the next training and practical sessions in October 2006 Skaala out Ww se focus uiis Ce AE We LMI JA wa 4 ves Q L ll u What other training in the fields of hydrology river modelling and water resources management would assist you in carrying out your work more effectively e IEN c A 62 oleco IES TRAINING EVALUATION FORM Training in flood hydrology river hydraulics and flood mapping Was the general content of the training about what you had expected A ves No How do you think the training will help you carry out any work related to flood hydrology river modelling and flood risk management in the future C Much more effectively M Slightly more effectively _ The same as before Did you rate the speakers as
95. ency curves are used for many design problems Ge vn wang Intensity frequency duration The relationship between rainfall intensity mm hour duration D hours and return period 7 is commonly expressed in the form i KT D a Where K x a and n are constants Intensity frequency duration Return period years 100 1 5 Duration hours oo HR Wallingford Working with water a Hyetograph A hyetograph is a plot of rainfall intensity against time interval It is useful because Rainfall intensity mm hour It can be used in the development of design storms to predict large floods The area under the hyetograph represents the total precipitation in the period The time interval depends on the size of the catchment Hyetograph Time hours Cee CE Ffeective rainfall Effective or excess rainfall is that rainfall that is neither retained on the land surface nor infiltrated into the soil The graph of effective rainfall versus time It can be used in the development of design storms to predict large floods The area under the hyetograph represents the total precipitation in the period The time interval depends on the size of the catchment HR Wallingford Working with water a HW How to estimate effective rainfall Rainfall intensity mm hour Rainfall excess Time hours i iki Runoff process 1 Usually water falling as precipitation retu
96. equency duration curves Understand the runoff process a HR Walingfor Skills acquired To estimate rainfall intensity from a rainfall intensity duration curves To calculate areal rainfall To estimate effective rainfall p HR Wallingford Working with water The Hydrological Cycle a nae i transpiration i i evaporation surface runoff A Tai naa J Site SESETAN i yoke ee eee groundwater flow Page 4 s Baa 7 S us Precipitation The term precipitation denotes all forms of water that reach the earth from the atmosphere The usual forms are e rainfall e snowfall hail e frost dew vate Working with water rawa Precipitation The term rainfall is used to denote precipitation in the form of water drops of sizes larger than 0 5 mm On the basis of its intensity rainfall is classified as Type Intensity 1 Light rain Trace to 2 5 mm hour 2 Moderate rain 2 5 to 7 5 mm hour 3 Heavy rain gt 7 5 mm hour a Hwa Measurement of rainfall intensity Methods by which rainfall intensity can be measured include Tipping bucket rain gauge Weighing bucket type Natural siphon or float type gauge Radar Ge rn wang Tipping bucket rain gauge a pae i p L HR Wallingford Working with water 4 Ae wang Precipitation Samoa 1961 1990 precipitation normals millimeters JAN FEB MAR APR MAY JUN JUL AU
97. er av HR wang Rainfall runoff exercise a HR Wallifig Exercise Rainfall 100 mm in 2 hours 250 TT 1 mT _Centroid of hydrograph Flow m s Time hours a HR Wallingford Exercise From the graph of the flood hydrograph estimate the following i The peak flood flow in m s ii The time to peak in hours iit The time base in hours iv The base flow in m s v The lag time in hours L LL Ol sinou uurL 8 Z 9 G r udeiB5oip u Jo pionu o sinou Z Ul WW OO Il Ju e2i OS OOL s uu mo 4 00 OSC Day 2 Vie Wallingford Working with water Na Wallingfo a An introduction to HEC HMS a HR Wallingford Learning objectives Understand the components of HEC HMS software Understand the different parts of the HEC HMS software interface Understand how to develop a HEC HMS project Ge irwan Skills acquired and reasons for using HEC HMS To know the functionality of the HEC HMS software
98. er Apia 6 1 INTRODUCTION The training in flood hydrology river modelling and floodplain mapping is part of an initiative to build capacity in flood management including forecasting monitoring modelling and mitigation within the technical agencies of the Government of Samoa The aim is to take the participants through the whole process of acquiring analysing and interpreting necessary datasets hydro meteorological and topography which provide the input for flood models to run the models and produce flood risk maps as a basis for the development of appropriate flood mitigation options The development of flood risk maps flood forecasting flood mitigation options and flood management guidelines will be part of the next training component planned for November 2006 Darren Lumbroso flood modelling and water resource specialist from HR Wallingford UK assisted by SOPAC staff delivered the training between 12 July 2006 and 3 August 2006 in the MNREM conference room in Apia The course participants brought their own computers and laptops to the training and the modelling software HEC HMS and HEC RAS had been installed on these computers 2 COURSE PARTICIPANTS The training was the first of its kind for all course participants The participants brought a variety of skills to the training ranging from weather forecasting hydrological data collection to environmental management Participants were also required to have a strong science ba
99. er Surface Floodway Left Bank Station Main Channel amp HR Wallingford Working with water a HRWalingor HEC RAS main window Fie Edt Run view Options Help Piws Steps in developing a hydraulic dun model with HEC RAS Start a new project Enter the geometric data Enter roughness data for cross sections Enter flow data and boundary conditions Performing the hydraulic calculations Viewing and printing the results Vise Wang Steps in developing a hydraulic a model with HEC RAS First draw the river schematic After the river schematic has been draw enter the cross section data Each cross section has a River name Reach name River station Description _ Vie Wallingford Working with water Ae Hwang What data is required to build a HEC RAS model Cross section data in the form of x and y coordinates Topographic details of the floodplain Boundary conditions what are these Ge ve waning se Hydraulic model boundary conditions All hydraulic models requiring boundary conditions Upstream boundary is normally formed by a flow input e g a steady flow or a flow hydrograph The downstream boundary can be formed by a water depth or stage vs discharge rating curve Geometric data window fei HR Wallingford Working with water Ni Basic data required for cross sections Exit Edt Options Plt Help River ButeC a E e e a EE Descrip
100. eriods boundary conditions Predict water levels for existing conditions Include proposed works in model Obtain water levels and compare with base data Iterate to optimum solution ae HR Walinglord How good is the answer How good is the data How good was the calibration How far have you extrapolated from the calibration conditions Be aware of uncertainties Sensitivity tests Realistic margin of safety f Exercise Approaches to river modelling Undertake a group discussion to decide what type of model s and approaches you would use in the three cases described below When deciding the best approach you will have to consider the following e What do you need to know e Scale how big is the area of interest e What is the minimum acceptable accuracy e How complex are the hydraulics e How will the results be presented and who wants to see them When you have decided what type of models to use you should also decide the approximate extent of river to be covered by the model Present you conclusions Case 1 Flood study for the town of Ba in Fiji A major new commercial site has been proposed for the town of Ba in Fiji that has the River Ba running through the centre of it Much of the development areas lay in areas that are likely to flood from the river A study was needed to determine design flood levels in the development areas The town is about 8 km from the sea and the river is tidal with a
101. es e Use Newton s second law e Has magnitude and direction e Used to calculate forces on structures e Can be applied where energy losses are large Scope for confusion av HR Wallingford Uniform Flow Vie Wallingford Working with water n Uniform flow profile R Water surface is approximately parallel to average bed slope Water level Distance a HR waning Uniform flow Central to understanding of open channel hydraulics Energy line water surface slope and channel bed are all parallel The depth is called Normal Depth Several assumptions in the analysis Rarely occurs in practice ZUrawanea Calculating uniform flow x Assumptions are e steady flow regular shape of cross section no change of velocity depth or slope with distance along channel rate of loss of potential energy balances work done against flow resistance but What is really happening Vie Wallingford Working with water AV sn sangeet Uniform flow equation Equation relating slope channel dimensions and velocity Q Ks 2 Q is discharge K is conveyance sis water surface slope Conveyance represents the flow capacity of the channel GY sn wang What is conveyance Links channel dimensions shape and roughness many formulae available Manning s equation K AR 2 3 n K is conveyance A is area R is hydraulic radius n is Manning s roughness coefficient
102. f the plot Plotting options similar to the cross section and profile plots are available for the rating curve plots Plot rating curves for various locations and practise using the available plotting options Hating Curve LS ie m Reload Data Reach Upper RiverSia 1 3 aiti Example 1 Steady flow Plan Existing 16 07 2006 sts x i 6 80 890 1000 1200 oO i Total mars Figure 15 Computed rating curve for River Station 1 9 for Main River Next look at an X Y Z Perspective Plot of the river system From the View menu bar on the HEC RAS main menu select X Y Z Perspective Plots A multiple cross section perspective should appear on the screen as shown in Figure 16 Try rotating the perspective view in different directions Now look at the tabular output Go to the View menu bar on the HEC RAS main window There are two types of table available a detailed output table and a profile summary table Select Detailed Output Tables to get the first table to appear The table should look like the one in Figure 17 This table shows detailed hydraulic information at a single cross sections Now bring up the profile summary table This table shows a limited number of hydraulic variables for several cross sections There are several types of profile tables listed under the Std Tables menu bar of the profile table window Some of the tables are designed to provide specific information at hydraulic structures e g
103. first step is to put together a Plan The Plan defines which geometry and flow data are to be used as well as providing a title and short identifier for the run To establish a plan select New Plan from the File menu on the Steady Flow Analysis window Enter the plan title as Proposed bridge steady flow and then press the OK button You will then be prompted to enter a short identifier Enter a title of BridgeSteady in the Short ID box The next step is to select the desired flow regime for which the model will perform calculations For this example we will be performing Subcritical flow calculations Make sure that Subcritical is the selected flow regime Saving the plan information is done by selecting the Save Plan from the File menu of the Steady Flow Analysis window EI Steady Flow Analysis Pin Eia ooo I Eg Geomety Fie Ein rives geometry Steady Flow Fie Eung conditions steadyliow Entel io compute water cuface profes Figure 11 Steady Flow Analysis Simulation Window Now that everything has been set the steady flow computations can be performed by pressing the Compute button at the bottom of the Steady Flow Analysis Simulation window Once the compute button has been pressed a separate window will appear showing you the progress of the computations Once the computations have been completed the computation window can be closed by double clicking the left corner of the window At this time the Steady Flow Si
104. for flood estimation exercise Year Annual maximum flow m s 1990 1991 1991 1992 1992 1993 1995 1994 1994 1995 1995 1996 1996 1997 1997 1998 1998 1999 1999 2000 2000 2001 2001 2002 2002 2003 2003 2004 2004 2005 2005 2006 Worksheet flood estimation Flood flow Return period T years T n 1 m Vie Wallingford Working with water Na Wallingfo a Exercise Occurrence of flooding within a certain time period Ge rwng The problem A bridge has an expected design life n of 25 years and is designed to pass a flood with a design return period T of 1 in 100 years without being overtopped i What is the probability R of the bridge being overtopped during its 25 year design life n If the designer only wants a 10 chance R of the bridge being overtopped during its 25 year design life n what flood return period T should the bridge be designed to pass a AS The equation Use the equation n R 1 1 1 T Where T is the return period of the design flood n is the design life of the bridge R is the probability of a T year flood occurring during n years The world s maximum floods It is not appropriate in a catalogue of this nature to attempt a systematic analysis of the published data nor to propose avenues of research that might be developed from the data It is appropriate however to define some index which permits an assessment of whether one flo
105. ge gained by the participants over the previous five and half days training EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States APPENDIX B Samoa Capacity Building in Flood Risk Management Vaisigano River Apia 11 Daily Schedule of Activities Wed 12 July Thur 13 July Fri 14 July Weekend Mon 17 July Tue 18 July Wed 19 July Thur 20 July Fri 21 July Weekend Mon 24 July Tue 25 July Wed 26 July Thur 27 July Fri 28 July Weekend Mon 31 July Tue 1 Aug Wed 2 Aug Thur 3 Aug 2pm meeting with Samoan Water Resources Division Hydrological Unit and Darren Lumbroso HR Wallingford consultant out of the UK Hydrology training course Hydrology training course River modelling and floodplain mapping training River modelling and floodplain mapping training Review of available hydro meteorological data Introduction to HEC HMS Review of available hydro meteorological data Introduction to HEC HMS Statistical analysis of available flow data for the Vasigano catchment Investigation of a regional flood frequency approach Development of rainfall runoff hydrographs for the Vasigano catchment Development of rainfall runoff hydrographs for the Vasigano catchment Introduction to HEC RAS and initial development of HEC RAS river model Development of HEC RAS river model Development of HEC RAS river model for the Vaisigano catchment Development of HEC RAS model for the Vaisigano c
106. h What do you think is more important in generating flooding in Samoa a long duration rain storm lasting several days or high rainfall intensities lasting for only a short period e g 2 to 3 hours What are the assumptions you make if you model a uniform steady flow What data do you need to build a hydraulic model of the Vaisigano River What do you understand by the term roughness in the context of river modelling What are its components and how can you assess it Why can you use a weir equation to transform water levels into flow How do you calibrate a hydraulic model of a river and why do you think this is important What are the main elements of uncertainty in hydraulic modelling of a river and how can you assess them 10 What is a flood hazard and how do you define flood risk How would you express the flood hazard of the Vaisigano River and the flood risks to Apia town on a map 11 What are the different options for reducing flood risk to an urban area Which do you consider to be the most appropriate for the Apia urban area 12 What are the different methods by which flood maps can be produced APPENDIX E Training Slides EU SOPAC Project Report 69d Lumbroso amp others Appendix E Training Slides Day 1 Vie Wallingford Working with water Na Wallingfo a Introduction to the training Ge rwng Introductions Who are you What do you hope to gain from the training and the project
107. h of cat tails along channel bottom any value of hydraulic radius up to 10 or 15 ft 3 to 4 6m Addition n for channel condition Degree of irregularity Surfaces comparable with n Smooth The best obtainable for the materials Involved 0 000 Minor Good dredged channels slightly eroded or scoured side 0 005 slopes of canals or drainage channels Moderate Fair to poor dredged channels moderately sloughed or 0 010 eroded side slopes of canals or drainage channels Severe Badly sloughed banks of natural channels badly eroded or 0 020 sloughed sides of canals or drainage channels unshaped jagged and irregular surfaces of channels excavated in rock Multiplier m for sinuosity As proposed by C S James m 1 0 s 1 m 0 57 0 43s lt s lt 1 7 m 1 30 s gt 1 7 Final Calculation of Manning s n n m n n n n n Manning s n roughness Reference Chow 1959 A A 1 A 2 Closed Conduits flowing partly full Metals a Brass smooth b Steel Lockbar and welded Riveted and spiral c Cast iron Coated Uncoated d Wrought iron Black Galvanized e Corrugated metal subdrain storm drain Non Metals a Lucite b Glass c Cement Neat surface Mortar d Concrete Culvert straight and free of debris Culvert with bends connections and some debris Finished Sewer with manholes Unfinished steel form Unfinished smooth wood form Unfinished rough wood form e Wood Stave Laminated treated
108. h sides of dressed stone in mortar random stone in mortar cement rubble masonary plastered cement rubble masonary dry rubble or riprap e Gravel bottom with sides of formed concrete random stone In mortar dry rubble or riprap f Brick Glazed In cement mortar g Masonary Cemented rubble Dry rubble h Dresses ashlar 1 Asphalt smooth rough J vegetal lining C d C Excavated or dredged a Earth straight and uniform Clean recently completed Clean after weathering Gravel uniform section clean With short grass few weeds Min 0 011 0 012 0 021 0 01 0 011 0 01 0 011 0 011 0 012 0 01 0 011 0 013 0 015 0 014 0 016 0 018 0 017 0 022 0 015 0 017 0 016 0 02 0 02 0 017 0 02 0 023 0 011 0 012 0 017 0 023 0 013 0 013 0 016 0 03 0 016 0 018 0 022 0 022 Norm 0 012 0 013 0 025 0 011 0 013 0 012 0 012 0 013 0 015 0 014 0 013 0 015 0 017 0 017 0 019 0 022 0 02 0 027 0 017 0 02 0 02 0 025 0 03 0 02 0 023 0 033 0 013 0 015 0 025 0 032 0 015 0 013 0 016 0 018 0 022 0 025 0 027 Max 0 014 0 017 0 03 0 013 0 015 0 014 0 015 0 015 0 018 0 017 0 015 0 016 0 02 0 02 0 023 0 025 0 02 0 024 0 024 0 03 0 035 0 025 0 026 0 036 0 015 0 018 0 03 0 035 0 017 0 5 0 02 0 025 0 03 0 033 D 1 a b b Earth winding and sluggish No vegetation Grass some weeds De
109. he Example_3 project is not still open from your previous work re open it When you have re opened it go to the File menu on the main window and select Save Project As In the Title box enter Example 4 1 in 100 year with bridge with sediment and in the File Name box enter Example 4 prj Note it is important that you check under the Options menu that the Unit System is set to SI i e Standard International or metric units The purpose of this exercise is to run the previous model you created with the proposed bridge with an unsteady flow and an increase in the river bed caused by the deposition of sediment The first step is to go to the Edit menu in the HEC RAS Main Window and select the Geometric Data editor The Geometric Data editor shown should open In the Geometric Data editor go to the Tools in the menu and select the Fixed Sediment Elevations option A window similar to that shown in Figure but without an increased in the bed level should open A geomorpholoigical study of the river has indicated that in ten years the upstream bed level at River Station 1 9 will increase from 70 0 m to 71 5 m and the downstream bed level will increase from 67 5 m to 70 0 m The purpose this exercise is to establish what effect this level of sedimentation will have on the 1 in 100 year flood levels In the Fixed Sediment Elevation window click on the Interpolate tab see Figure 1 make sure you window looks exactly the same as Figure 1 The
110. he flood with return period T is referred to as the T year flood The probability P of a T year flood happening in any one year is 1 T s HR Wallingford Working with water a Hwang Statistical analysis of data 1 Produces flood estimates based on recorded historical pattern of runoff events 1 Select annual maximum floods from the period of record e Ensure independence e Use water years 2 List events in descending order and give rank m 3 Count total number of events in series n GY rn anger Statistical analysis 3 _ Probability P associated with each event can be computed from a number of formulae eg P m or P m 0 44 n 1 n 12 To predict flows for any return period need a graph However plotted on graph paper P against Q is unlikely to follow a straight line Several theoretical distributions have been proposed e g Gumbel Generalised Logistic Log Pearson Vie Wallingford Working with water PPr Statistical analysis 4 Rank Flood flow Annual Return period T m m s probability years P m n 1 0 0196 0 0392 0 0588 0 980 AS Statistical analysis 5 If instead of plotting P against Q you plot the reduced variate y against Q where y in In T T 1 Then for Gumbel the points should be a straight line Extrapolate line to predict design floods GY in vaingerd Statistical a
111. hese Meteorologic models are as follows 1 in 100 year 1 hour duration storm with the file name 1h_100y_ARI 1 in 100 year 2 hour duration storm with the file name 2h_100y_ARI 1 in 100 year 3 hour duration storm with the file name 3hr_100y_ARI 1 in 100 year 4 5 hour duration storm with the file name 4 5hr_100y_ARI 2001 flood with rainfall data from Dr Yeo s study on the 2001 flood with the filename 2001 flood 2001 flood with rainfall data from the Meteorology Division s on the 2001 flood with the filename 2001 flood Meteo The first step is to run the HEC HMS model with all for all of these different rainfall events Refer to the HEC HMS manual if you are having difficulties For each run view the hydrograph that is produced at Junction 8 of the model Which of the 1 in 100 year storms generates the highest peak flow Export the data for each of the hydrographs to a spreadsheet Now use these six hydrographs to run the HEC RAS model you built in Exercise 5 Refer to the HEC RAS user manual if you are having difficulties importing this data Which of the 1 in 100 year flood hydrographs gives you the highest water levels HEC RAS exercises Exercise1 Setting up a steady flow river model Using Windows Explorer set up a sub directory on your computer called C HEC RAS Examples Open the HEC RAS proeram by double clicking on the HEC RAS Icon The main window should appear as shown in Figure 1 Hl HEC RAS 3 1 3 Fie Edt Run Wew Opt
112. ilename d work Samoa Example Sdss 1 DS Mixed Flow Regine see menu OptionsMined Flow Options Figure 6 Unsteady Flow Analysis Simulation Window Once the model has finished all of the computations successfully you can begin viewing the results Several output options are available from the View menu bar on the HEC RAS main window including Create section plots Profile plots General plots Rating curves X Y Z perspective plots Detailed tabular output at specific cross section cross section table Limited tabular output at many cross sections Let s start by looking at Stage and Flow hydrographs Go to the View menu and select Stage and Flow Hydrographs Investigate the shape of the various water level and flow hydrographs for the different cross sections When you have done this go to the View menu and select Water Surface Profiles Click on the black arrow and you will see an animation of how the water surface changes with time Next look at an X Y Z Perspective Plot of the river system From the View menu bar on the HEC RAS main menu select X Y Z Perspective Plots A multiple cross section perspective should appear on the screen Try rotating the perspective view in different directions Now press the black arrow and you should see an animation of how the water surface changes with time Now look at the tabular output Go to the View menu bar on the HEC RAS main window There are two types of table avail
113. in AV sn samme Water surface profile Plot of stage against distance along the channel Water surface f Ss o gt Ka G D T gt 8 z 1500 2000 Distance m GV sr sang Hydraulic radius Represents the shape of the cross section Ratio of Area A to Wetted Perimeter P R A HR Wallingford Working with water i Flow resistance The effect of the river bed and banks to slow down the water flow Causes Large scale Vegetation feature gt Dune Ripple RR ST VE ls REOS Bey LAB DL EER AEAN Z Sediment Trash Vie Wallingford Working with water Ge vn wang Probability and frequency Probability The chance that some event e g a flood this year might happen Frequency The rate of incidence of an event especially from observations Often data on frequency is used to estimate probability GV sn samme Flood probability Annual Probability P e The chance that the condition will be equalled or exceeded in any year e Sometimes expressed as a percentage Return Period T e The average interval in years between occurrences of the condition Relationship eT 1 P Vie Wallingford Working with water Na Wallingfo a Precipitation and runoff AVe Learning objectives Understand different forms of precipitation Understand methods to estimate areal rainfall Understand rainfall intensity fr
114. indow and go to Save Geometric Data As Geometry with bridge sediment weir The next step is to put together a Plan The Plan defines which geometry and flow data are to be used as well as providing a title and short identifier for the run To establish a plan select New Plan from the File menu on the Unsteady Flow Analysis window First open the Unsteady Flow Analysis window by going to the Run menu and selecting Unsteady Flow Analysis Enter the plan title as 1 in 100 bridge sediment weir and then press the OK button You will then be prompted to enter a short identifier Enter a title of 100Weir in the Short ID box The next step is to fill in the Unsteady Flow Analysis Window as shown in Figure 5 NOTE The Geometry file and short ID will be different from that shown in Figure 5 Now press the Compute button and the model should run Fa Unstead y Flow Analysis Options Help Plan I m 100 Short ID lini00unsd Geometry File Geomeby with proposed bridge Unsteady Flow Fle Tint 00 year flow Programs to Run Plan Descqiption z Geomety Preprocessor w Unsteady Flow Simulation w Post Processor Simulation Time Window Starting Date 25Jul2006 Starting Time 0000 Ending Date 25 Jul2006 Ending Time fos Oo sesama ae 5 Minute gt Hydrograph Output Interval Detailed Output Intervat 5 Minute DSS Output Filename d work Samoa Example Sdss 1 DS Mixed Flow Regine see menu OptionsMined Flow O
115. ingford Working with water uswa Uncertainty in river modelling How to analyse the uncertainty in river modelling Assess the factors that contribute to the uncertainty Survey accuracy Model calibration Resolution of the river model AU He wang Estimating uncertainty in 1 D river modelling Numerical model resolution a HR Wallingford Cross section spacing a key parameter Depends upon river regularity and slope ratio of areas between sections 2 3 to 3 2 ratio of conveyance between sections 4 5 to 5 4 Page 26 Estimating uncertainty in 1 D river modelling Model cross section spacing Slope 1 in Section Spacing m 300 to 1 000 75 1 000 to 3 000 200 3 000 to 10 000 500 10 000 1000 Contribution to overall uncertainty less than 30 mm rer HR Wallingford Working with water Pawana Estimating uncertainty in 1 D river modelling Etotal E 2 E Eq E is uncertainty in metres E Topography and roughness uncertainty E Calibration uncertainty E Discretisation i e section spacing uncertainty Eriak 1 7 Erota S _ A il stimating uncertainty a in 1 D river modelling E Topography and roughness formula depends on survey method Calibration uncertainty E is estimated from E 1 N XX H model Hobs x Max Qr Q gt N is the number of observation Hops is the observed water leve
116. into two main components e Fast direct Slow Sometimes expressed as a percentage A a amp HR Wallingford Working with water GE eager Stage Stage is the water level measured above a datum usually denoted by the symbol h EPan Discharge Discharge is the rate of volume of water flowing through a river section usually denoted by the symbol Q Measured in cubic metres per second or cumec or e m3 s GY in veingsed Mean flow velocity Discharge divided by flow area NER The velocity is at right angles to the cross section measured in units m s It is a typical value for the section In flood conditions we may calculate average velocities in the channel and for the flood plains Page 6 A a amp HR Wallingford Working with water Gere wang Velocity distribution Variation across a section ee Max V Pr Variation with depth Ni s A stage versus discharge rating curve Plot of stage against discharge 0 bankfull 30 40 Discharge m s GV sn suing Conveyance K A measure of the capacity of a river Conveyance K depends on stage h Q K h s 5 Q is discharge s is water surface gradient s Vie Wallingford Working with water ae HR Wallingford Backwater influence The upstream effects of a control on water level e g e ponding behind a weir e raised water level from constricting the flood pla
117. ions Tp C L S Where C and n are constants related to the catchment S is the slope of the river L is the distance the water has to travel From observed values of lag time between centroid of rainfall and flow pea GY rena Hydrograph computation 1 Construct unit hydrograph 2 Estimate percentage runoff GY sn waned Percentage runoff Percentage runoff is the proportion of the total rainfall input which shows up as rapid response runoff in the river It is estimated from Empirical equations e g US Soil Conservation Service Curve Number Method Observed values if these are available Vie A Working with water a HR WalingoR Hydrograph computation 1 Construct unit hydrograph 2 Estimate percentage runoff 3 Calculate design storm event rainfall 4 Distribute according to chosen profile AV sn sangeet Design storm event Design storm duration D Design storm depth P Design storm profile a HR Wallingford Design storm event x Estimate the critical storm duration in hours Storm Depth is taken from the design rainfall Rainfall depth mm Time hrs Working with water a HR wang Hydrograph computation 1 Construct unit hydrograph 2 Estimate percentage runoff 3 Calculate event rainfall 4 Distribute according to chosen profile 5 Convolute net rain and UH A He vemeee R
118. ions Help Figure 1 HEC RAS main window The first set in opening a HEC RAS application is to start a new project Go to the File menu on the main window and select New Project The New Project window should appear as shown in Figure 2 New Project Selected Fokder Default Project Folder File Hame Steady flow Example Tri dt work i HEC RAS examples L RAS exam ples OK Cancel Heip Create Folder 3 d buora_dl el dive and path then enter a new project tile and file nane Figure 2 New project window Set the drive to the C HEC_RAS_Examples directory In the Title box enter Example 1 Steady Flow and in the File Name box enter Example_1 prj Note it is important that you check under the Options menu that the Unit System is set to SI i e Standard International or metric units The next step in developing a hydraulic river model using HEC RAS is to enter the geometric data This is done by selecting the Geometric Data from the Edit menu on the HEC RAS main menu Once this option is selected the geometric data window will appear as shown in Figure 3 Geometric Data Sizes Fie Edt View Tables Took Help Tools River forage Sa Pump pg eae as aa ene Sat SFE Figure 3 Geometric data window In this example a simple hydraulic model of a river is going to be developed as shown in Figure 4 Draw the river system schematic by performing the following step
119. ischarge Water surface slope 0 000695 1 1439 Average cross sectional area 77 59 m Average flow width 29 m Average hydraulic radius 2 42 m Description of channel Bed material gravel with shallow rock step Banks grass with mature alder sycamore and ash trees Left and right flood plains are short grass pasture Plan Drakelow N O SASS N SSS ANON S ate Ae eS eS QO A TAS See A z x SE SSS NANS S _ SARAH oS SS ENS ASS SENSE SESS SOC CUA Soe SS NN ASN NNN ANAN SESS NN SEN ESS NY ES RARAN x SSN T DAIS SA A E x Se Tate L SHASASSA x SSS SOON astaw ANANAS SASS NN SNA KWA N ANDY Ses Nt SSS As SS ENS SRR SF REN EISAMINA SSS ESS NS SSX RNR RVR SRS SASASSSASSaAS a SANRA SSSSSS SSS sS SS SS ae WEES N ENS SS SASS lt lt s ANS SSS SSS SSS s s ST SS REE ESA EE ENN ET OR SVs AN Elevation MAOD a SES SLE SSK TSS XA SNe S Se NES SSS SSSSS SIMS sS ce SSS Seso SSES PSSS Se WR LAE AVS ASSAN 0 N NSC AS SS N TRON SEES SSES A SSS Ni ANA SEN SA ONN SSS WN x SSAA Ss Se Loree w SS SK SASS SRS w A A SESS sss D RS Co SESS SSS s ms at x ORULA NRANANS NAS EEN Stata X RY Ny CSS se RARS N SD NN ANRA a SASS SS Sa Ste SER SAD SS SS SSS SS RRS SS See S s SRS RRR SS ANNES SSE SSS 2 SSS KAN WA T NN AN N eA Width m Plan and cros
120. ith that event Risk probability x consequence 3 July 2006 Introduction to flood hydrology river modelling and floodplain mapping Risk mapping Roughness Runoff Scenario Source Stage Steady flow Stakeholders Stream power Surge conditions Trash screens T year flood Uncertainty Unit hydrograph a HR Wallingford The process of establishing the spatial extent of risk combining information on probability and consequences Risk mapping requires combining maps of hazards and vulnerabilities The results of these analyses are usually presented in the form of maps that show the magnitude and nature of the risk The effect of impeding the normal water flow of a channel by the presence of a natural or artificial body or bodies bed substrate biotic e g vegetation or abiotic mineral e g bank The amount of rainfall that drains into the surface drainage network to become stream flow A plausible description of a situation based on a coherent and internally consistent set of assumptions Scenarios are neither predictions nor forecasts The results of scenarios unlike forecasts depend on the boundary conditions of the scenario The origin of a hazard for example for a flood it may be heavy rainfall strong winds tidal surge etc Equivalent to water level Both are measured relative to a specified datum A flow in which the magnitude and direction of the specific discharge are const
121. ity Building in Flood Risk Management Vaisigano River Apia 4 ACKNOWLEDGEMENTS The European Commission provided funding for this project task under the framework of the SOPAC EU Reducing Vulnerability Project Additional funding was kindly provided by the EU funded Samoan Water Sector Strengthening Program WaSSP and the SOPAC Water Sector The work was carried out in close cooperation with the Ministry for Natural Resources Environment and Meteorology MNREM and appreciation for managerial support goes to Ausetalia Titimaea Meteorology Amataga Penaia Water Resource and Nadia Meredith WaSSP manager Special thanks to Silver Yance flood modelling consultant of the ADB project for the very helpful co operation and the exchange of data and model results EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States Samoa Capacity Building in Flood Risk Management Vaisigano River Apia 5 EXECUTIVE SUMMARY Floods are a well recognised risk in Samoa frequently causing major damage The floods in April 2001 alone caused an estimated 11 Million Tala in direct losses The aim of this project task is to build capacity in flood management to reduce future losses by strengthening the capacity of technical agencies in flood forecasting mapping and mitigation This report summarises the training efforts by a joint HR Wallingford SOPAC team working together with technical speciali
122. ity of existing channel b design for river training scheme river diversion channel enhancement river restoration Nae Channel plan form meanders Independent variables are a water discharge b sediment discharge c sediment characteristics d valley slope Solution for plan form and cross sectional shape can be obtained Ge unwangaq un Bed and bank features Typical features associated with meandering rivers Cross section shape on bend deeper on outside of bend Pool and riffle sequences linked to plan form Occurrence of point bars deposits of sediment on inside of channel bends Undercutting of banks on outside of bends Ge iranga Elements of channel form PLAN OF MEADER CHANNEL Thoiweg Poor _ S107 Chonnet j Widtas PLAN OF STRAIGHT CHANNEL a HR Walingior Stream power e Stream power is the power or rate of work required by the river to transport water and sediment e Important independent variable which affects channel stability and river morphology e Stream power is a function of gradient and discharge Stream power a HR Walinga Physical impacts straightening e Straightening a meandering stream increases slope locally e Increased slope causes increased sediment transport e Increased sediment transport causes upstream degradation e Increased sediment transport causes downstream deposition where slope flattens in the nat
123. iver modelling and flood risk management in the future _ Much more effectively C Slightly more effectively _ The same as before Did you rate the speakers as Z Good Reasonable Poor Were the presentations Too technical Z About right Not technical enough What was your overall assessment of the training A Excellent Good Reasonable Poor What was your assessment of the training material L Excellent _ Good _ Reasonable _ Poor How did you find the training exercises J Too challenging About right Too easy What were the strengths and weaknesses of the training apat epetan Kors WU Qed ah re Dam was No Qud Q Ke C lt COS Veacts S YU0 J Wud NU Awak sss DOAN W SS LW ould EE Goad A QO Colt x WL US SQ SOMOQ BAU WL xU OGL Kah Kook ng Goold Sol a Ore WL wR KA What areas of flood hydrology river modelling and flood risk management do you think should we concentrate on during the next training and practical sessions in October 2006 gt OR MATA VW WOM Loa dior nay Wong WAQA A QA LAX d Atelopus p an AN g pLear D Ova qa Kook wazad SAN kay s Ria uM AQ TESA LAL Rosso ONS cakah WAS TT woddls AS What other training in the fields of hydrology river modelling and water resources management would assist you in carrying out your work more effectively WATERTON DLE BLEAK Bh Vena me ote grery SOK Ay WR waqu AN U be Ste voit KY
124. j Edi arth ej EL Inline structure button T Lal zj 0 4288 0 3409 Figure 1 Geometric data window showing inline structure button Inline Structure Data Geometry with bridge se Sielta Reach Dae alte IE E HH Upstream X 18 _ Upstream channel length 500 im oa XO L binh TE qay utton Select the mear for inina struchwe eding Figure 2 Inline structure window In the Inline Structure window go to the Options menu and select Add an Inline Structure option The popup box shown in Figure 3 should appear Add a River Station of 1 71 in this popup box and change the Pilot Flow box from 0 to 10 Inline Structure Data Geometry with bridge se Mele Rive Man River Arop Feact upper gt Rive Sta 1 71 t 3 _ Up tream channel length 500 m HEC RAS Pilot flow Figure 3 Popup box for entering the river station for an inline structure Next click on the Weir Embankment button shown in Figure 2 The window shown in Figure 4 should appear Add the data shown in Figure 4 to your model so that it is exactly the same as shown in Figure 4 lahe Structure Weir Station Lievation tditar weg Crest Sha w Brosd Crested C Ogee Or Cancel Chea J Erte dance between uptieam crot sector and deck maderay ml Figure 4 Inline structure weir station elevation editor Once you have checked that this data is all correct go to the File menu in the Geometric Data W
125. l H oqe iS the modelled water level Q is the design return period Qc is the calibration flow Pirwan Estimating uncertainty in 1 D river modelling The discretion uncertainty Ed is estimated from E 0 1 D AX L D is the bankfull depth L is the backwater length AX is the section spacing a HR Wallingford Working with water Pirwan Topography and roughness Conventional field survey of floodplain topography E 0 12 HD 6 S911 5Nr 65 E 1 7 E 8 Notation HD Hydraulic Mean Depth S River Slope Nr Roughness reliability number max Ge vn waningse Topography and roughness Aerial survey providing spot levels on section lines E 0 12 HD S011 SNr Sn if Nr gt 0 E 1 5 S049Sn083 if Nr 0 E 1 7 E 8 S is the river slope max Sn Survey accuracy number Ge vn wang Topography and roughness Floodplain topography determined from contour maps E 0 63 HD 35 S 13 Nr Sn if Nr gt 0 E 1 4 S023 Sn1 18 if Nr 0 Emax 2 1 E 8 max Vie Wallingford Working with water Ge vn waning sti Survey accuracy number Sn Contour Spot Sn interval accuracy 250 mm 50 mm 500 mm 100 mm 1000 mm 250 mm 2000 mm 500 mm AP vms Calibration reliability number Nr Mean level drop Reliability number m between gauges Nr less than 1 0 0 0 1 0 0 1 4 0 0 4 10 0 7 15 0 8 20 0 9 no calibration data 1 0 a HR Wallingford
126. l training was undertaken over a period of five and a half days The training course was developed using material that has been tried and tested by HR Wallingford Ltd over a number of years It should be noted that considerable effort was made to modify the material to make it specifically relevant to the South Pacific and Samoa A breakdown of the formal lectures and exercises is given in Appendix A and a daily schedule of activities is provided in Appendix B lt is important to note that between Monday 17 July 2006 and Friday 21 July 2006 the participants used the knowledge they had gained on the flood hydrology course to work with Darren and Michael in analysing the flood hydrology of the Vaisigano River catchment Between Friday 28 July 2006 and Wednesday 3 August 2006 the participants on the course used the skills they had acquired to commence constructing a one dimensional HEC RAS hydraulic model of approximately 1 6 km of the Vaisigano River upstream of its mouth at Apia Harbour 4 COURSE MATERIAL As part of the training comprehensive sets of source material and lecture notes were provided to the course participants as hard and partly as softcopies e Acomprehensive set of training notes comprising aglossary of key terms used in flood risk management Appendix G colour copies of all the slides used for the presentations Appendix F the material required for the training exercises and several papers relevant to hydrological
127. me 2122905 1017 18 NOTE 0178 Opened tatin mosa Caitro 1 at tawa H ArI 101724 Message log Watershed explorer HEC HMS 3 0 1 D work Samoa HEC_HMS castro CAS TR OSUSl eee amp 0 w s 4 Fie Edt View Components Parameters Compute Resuts Tool Basin Hame Castro 4 Element Hame Subbasin 3 Downstream Reach 2 Area KM2 5 62 r Loss Method nisl sta x Transform Method Snyder Unit Hydrograph x amp HR Wallingford Working with water Ge rn wang se Message log WARNING 10611 Specified time window contains partial intervals for gage Fire Dept End time adjusted to 16Jan1973 09 40 NOTE 10008 Finished opening project castro at time 21 Jun2006 10 17 18 NOTE 10179 Opened basin model Castro 1 at time 21 tun2006 10 17 24 a HR Wallingford Desktop EPn Developing an HMS model Create a new project Input data needed by the basin and or the meteorologic model Define the physical characteristics of the catchment by editing the basin model Select a method for calculating subbasin precipitation a AV HR Walon Working with water a HR Developing an HMS model Define the control specifications Combine a basin model meteorologic model and control specifications to create a simulation View the results and modify the basin model meteorologic model or control specifications as needed Ge re wsng Creating a new
128. mulation window can also be closed Once the model has finished all of the computations successfully you can begin viewing the results Several output options are available from the View menu bar on the HEC RAS main window including Create section plots Profile plots General plots Rating curves X Y Z perspective plots Detailed tabular output at specific cross section cross section table Limited tabular output at many cross sections Let s start by plotting a cross section Select Cross Sections from the View menu bar on the HEC RAS main window This will automatically bring up a plot of the first cross section on the Main River number 1 9 see Figure 12 You can also step through the plots by using the up and down arrow buttons Several plotting features are available from the Options menu bar on the cross section plot window These options include zoom in zoom out selecting which plans profiles and variables to plot and control over lines symbols labels scaling and grid options From the Options menu on the cross section editor select the Profiles option Select the three available profiles Select different cross sections to plot and practise using some of the features available under the Options menu bar 2 a a c me T xrz srrr rr r rrF rs r x s Sen Sey Ma ere S s aA Select Profiles Bva Profile Digests pase hs ana ET a en Day nh i paa River Main Arver ba Fal rje 5 i ls Y 50 yeas
129. n Supple seedling tree switches such as willow cottonwood or salt cedar where the average depth of flow is 3 to 4 times the height of the vegetation Moderate influence n 0 010 to 0 025 Brushy growths moderately dense similar to willows 1 to 2 years old dormant season along side slopes of channel with no significant vegetation along the channel bottom where the hydraulic radius is greater than 2 ft 0 6m Turf grasses where the average depth of flow is 1 to 2 times the height of vegetation Stemmy grasses weeds or tree seedlings with moderate cover where the average depth of flow is 2 to 3 times the height of vegetation High influence n 0 025 to 0 050 Dormant season willow or cottonwood trees 8 to 10 years old intergrown with some weeds and brush none of the vegetation in foliage where the hydraulic radius is greater than 2 ft 0 6m Growing season bushy willows about 1 year old intergrown with some weeds in full foliage along side slopes no significant vegetation along channel bottom where hydraulic radius is greater than 2 ft 0 6m Very high influence n 0 050 to 0 100 Turf grasses where the average depth of flow is less than one half the height of vegetation Growing season trees intergrown with weeds and brush all in full foliage any value of hydraulic radius up to 10 or 15 ft 3 to 4 6m Growing season bushy willows about 1 year old intergrown with weeds in full foliage along side slopes dense growt
130. n River press the Normal Depth button A pop up box will appear requesting you to enter an average energy slope at the downstream end of the river see Figure 10 Enter a value of 0 0004 m m then press the Enter key This completes all the boundary condition data Press the OK button on the Boundary Conditions form to accept the data Steady F bow Boundary Conditions t Set bounding foe all profiles C Set boundary for one profile at a time Pu lasla E dened Baura L r Caca Dela TU Ran Delete r Figure 10 Steady Flow Boundary conditions The last step in developing the steady flow data is to save the data to a file To save the data select the Save Flow Data As option from the File menu on the Steady Flow Data Editor A pop up box will prompt you to enter a description of the flow data as shown in Figure 11 For this example enter Existing conditions steady flow Once the data is saved you can close the Steady Data editor Save Flow Data As File Hame Selected Folder Dels Project Fodder EOE siegh lon E dwak HEC FAS examples Eung condong sheady fow Carcel Create Fodder ucua d w pana diire ond path adena rew Tithe Figure 11 Saving the flow data Now that all the data has been entered we can calculate the steady water profiles To perform the simulations go to the HEC RAS main window and select Steady Flow Analysis from the Run menu The Steady Flow Analysis win
131. n on the Geometric Data window Once this button is pressed the Cross Section Data Editor will appear as shown in Figure 2 Cross Section Data 4 i x No Data for Plot Figure 2 Cross Section Data Editor In the Cross Section Editor window shown in Figure 2 go to the Options window and Add a new Cross section An input box will appear to prompt you to enter a River Station Identifier This must have a numeric value This numeric value describes where each cross section is located relative to each other within a reach Cross sections are located from upstream the river station with the highest numeric value to downstream the lowest river station The new cross section that you will add to the model will be labelled 1 51 Add the cross section data from the Excel spreadsheet called HEC_RAS_Example_data xls in the Worksheet entitled Bridge Data In order not to extend the total length of the river when you have entered the new cross section you will need to change the Downstream Channel Reach Lengths for the cross section with the station label 1 6 Open cross section 1 6 and change the Downstream Reach Lengths for the LOB Channel and ROB from 500 to 30 as shown in Figure 3 Cross Section Dala Eoisting river peometry Ext Edt Options Pict Help ire annae Appl Data a Mal Birk Keep Prev Pisis _ Clear Prev masma 2 OF dy ya bap abd m f DE gpa 5 T _ RDB fe os 006 Left Rar
132. nalysis 6 1200 Estimate of 1 in 200 year flood is 1003 m s a P E NAE AEA E T Naas none teense tae aan E E Se 2 Estimate of 1 in 100 year flood is 918 m s gasas a nA ERE A EE E N E AE S aa Estimate of 1 in 50 year flood is 833 m s i Flow m s Return period years HR Wallingford Working with water Ae rwng Flood frequency plot oo A flood frequency curve relates the size of a flood to its frequency of occurrence Confidence e Use knowledge of historical floods providing no missing information about extreme floods e Increase n ae V P ee WN N x Ge irwan Some useful y values Return period T Reduced variate years y T 1000 years y 6 91 T 100 years y 4 60 T 50 years y 3 90 T 25 years y 3 20 T 10 years y 2 25 T 5 years y 1 50 a Hwa Sources of uncertainty Choice of statistical distribution fitting procedure etc Duration of records normally so short that it is difficult to extrapolate with confidence Flow series may not be homogeneous e g Change in data collection method position datum Land use change in the catchment e g development Climate change v HR Wallingford Working with water Pirwan Sources of uncertainty Ge rwng Regional flood frequency analysis Regional analysis adopted when data is limited Use flood flows from a hydrologic
133. next step is to add the value of 71 5 in the Upstream Elevation box and the value of 70 0 in the Downstream Elevation box Now click the Apply Sediment Elevations to Selected Range button Now click on the Update Plot button You will see the bed level increase as shown in Figure 1 Now click on the OK button Now go to the File menu in the Geometric Data window and chose Save Geometric Data As Save the new geometric data as Geometry with proposed bridge sediment The next step is to put together a Plan The Plan defines which geometry and flow data are to be used as well as providing a title and short identifier for the run To establish a plan select New Plan from the File menu on the Unsteady Flow Analysis window First open the Unsteady Flow Analysis window by going to the Run menu and selecting Unsteady Flow Analysis Enter the plan title as 1 in 100 year flow with sediment and then press the OK button You will then be prompted to enter a short identifier Enter a title of Sediment in the Short ID box The next step is to fill in the Unsteady Flow Analysis Window as shown in Figure 2 Now press the Compute button and the model should run Cross Section Fixed Sediment Elevation River Main Rives Reach U Upper Main River Upper 1000 BaF Bs LALE Bale Shawne Dir tica 4 SetRangeofValues SelectedArea Goba Eds Beep Ir O O Upstream RS z J t Haat a saa pe __Copy wet Downstream
134. nse weeds or aquatic plants in deep channel Earth bottom and rubble sides Stony bottom and weedy banks Cobble bottom and clean sides c Dragline excavated or dredged No vegetation Light brush on banks d Rock cuts Smooth and uniform Jagged and irregular e Channels not maintained weeds and brush uncut Dense weeds high as flow depth Clean bottom brush on sides Same highest stage of flow Dense brush high stage Natural streams Minor streams top width at flood stage lt 100 ft Streams on plain I Clean straight full stage no rifts or deep pools Same as above but more stones and weeds Clean winding some pools and shoals Same as above but some weeds and stones Same as above lower stages more Ineffective slopes and sections Same as 4 but more stones Sluggish reaches weedy deep pools Very weedy reaches deep pools or floodways with heavy stand of timber and underbrush Mountain streams no vegetation in channel banks usually steep trees and brush along banks submerged at high stages I Bottom gravels cobbles and few boulders 2 Bottom cobbles with large boulders Min 0 025 0 030 0 033 0 035 0 040 0 045 0 050 0 075 0 030 0 040 0 023 0 025 0 03 0 028 0 025 0 03 0 025 0 035 0 025 0 035 0 05 0 04 0 045 0 08 0 025 0 03 0 035 0 03 0 035 0 04 0 035 0 05 0 035 0 04 0 08 0 05 0 07 0 1 Norm 0 030 0 035 0
135. nter the boundary conditions press the Reach Boundary Conditions button at the top of the Steady Flow Data editor The boundary conditions editor will appear as shown in Figure 10 except yours will be blank the first time you open it Boundary conditions are necessary to establish the starting water surface at the ends of the river system A starting water surface is necessary in order for the HEC RAS program to begin the calculations In a subcritical flow regime boundary conditions are only required at the downstream end of the river system If a supercritical flow regime is going to be calculated boundary conditions are only necessary at the upstream end of the river system If a mixed flow regime calculation is going to made then boundary conditions must be entered at all open ends of the river system In this example it is assumed that the flow is subcritical throughout the river system Therefore it is only necessary to enter a boundary condition at the downstream end of the Main River Boundary conditions are entered by first selecting the cell in which you wish to enter the boundary condition Then the type of boundary condition is selected from the four available types listed above the table The four types of boundary conditions are Known water surface elevations Critical depth Normal depth Rating curve For this example use the normal depth boundary condition Once you have selected the cell for the downstream end of the Mai
136. obability of flooding or Annual Average Damages based on the full range of floods that could occur Flood study A comprehensive technical investigation of flood behaviour Fluvial Relating to rivers Freeboard The height above a defined flood level typically used to provide a factor of safety in for example the setting of floor levels and embankment crest levels Hazard A physical event phenomenon or human activity with the potential to result in harm A hazard does not necessarily lead to harm Hazard mapping The process of establishing the spatial extents of hazardous phenomena Heterogeneity Similarity e g heterogeneous catchments will have similar characteristics Hydrograph A graph that shows for a particular location the variation with time of discharge discharge hydrograph or water level stage hydrograph during the course of a flood 2 2 July 2006 Introduction to flood hydrology river modelling and floodplain mapping Hydrometeorology Interpolation Inundation Iteration Pathway Peak discharge Precision Rating curve Receptor Regression Resistance Return period Risk a HR Wallingford Specialist branch of hydrology the study of precipitation and evaporation Estimation of values based on a relationship within the limits of observations Flooding of land with water Process of refining a value to an acceptable level of accuracy by using the output of one calculation as
137. ocity and Froude number we HR Wallingford Working with water GY verge Work in a group Choose some cases and share the results in the group e How sensitive is discharge to depth e How sensitive is velocity to depth e How sensitive is Froude number to depth What happens for different slopes and roughnesses What is the critical slope for n 0 02 Page 4 Ge rn wings The worksheet Worksheet for Exercise on Principles in Hydraulics Manning s n Slope Width Depth Wetted Hydraulic Discharge Velocity m s Froude Perimeter m Radius m m s Number LO N O pa S ui snipey ui d9J uid q uu 1 quinN pnoi3g s w jiSol A S w aBseyosiq o ilneup H D AA p 1V og UIDIAA u S OEY odojs asa us buluuel jauueyd sejnHbueyoy so1lnespAy Ul s l diSuiid UO BSID1BX9 10 JOOUSYION LO N O pa S ui snipey ui d9J uid q uu 1 quinN pnoi3g s w jiSol A S w aBseyosiq o ilneup H D AA p 1V og UIDIAA u S OEY odojs asa us buluuel jauueyd sejnHbueyoy so1lnespAy Ul s l diSuiid UO BSID1BX9 10 JOOUSYION LO N O pa S ui snipey ui d9J uid q uu 1 quinN pnoi3g s w jiSol A S w aBseyosiq o ilneup H D AA p 1V og UIDI
138. od defence works on the hydrograph Figure 3 shows the stage versus discharge relationship at the site before development widening and straightening Sketch the impact of the development and the flood defence works on this relationship a HR Wallingford Figure 2 A Discharge a HR Wallingford Figure 3 A Level m AOD Flow m3 s a HR Wallingford Task 3 There were possibly other options for managing the increased run off from the new development Describe these options and discuss the limitations and likely positive and negative impacts that they may have had Include a sketch of the impacts on the post development hydrograph Figure 4 of the different options a HR Wallingford Figure 4 A Pre development __ Post development Discharge Vie Wallingford Working with water Na Wallingfo a An introduction to HEC RAS a HR Wallingford Learning objectives Understand the components of HEC RAS software Understand the different parts of the HEC RAS software interface Understand how to develop a HEC RAS project Ger waning Skills acquired and reasons for using HEC RAS To know the functionality of the HEC RAS software To appreciate how to develop a simple river model using HEC RAS a HR wana HR Wallingford Working with water Background to HEC RAS HEC RAS Hydrologic Engineering Center s River An
139. od is larger than another that was perhaps observed on a different river In this respect the Francou index k Francou amp Rodier 1967 used in the first edition has been used again in this edition It is given by k 10 1 log Q 6 log A 8 where Q is the largest flood in m s and A is the catchment area in km Fifty four floods with k values greater than 5 were selected from a total of some 1500 floods in the Catalogue These are given in the Table and are plotted logarithmically in the Figure below giving an envelope curve with the following relations O 500A for values of A greater than 90 km and Q 100 4 for values of A less than 90 km It is apparent that the straight line envelope curve above 90 km has a k value of approximately 6 with some points lying above the line and some below it The straight line below 90 km has a value of approximately 5 6 with some departures from this value It will be noted that there are no European countries on the envelope curve most floods in Europe have k values between 3 and 5 Plot of discharge Q against catchment area A for the world s maximum floods Discharge Q m s XIV 105 10 104 Mexico USA N Caledonia 10 ppines apan N Korea S Korea Australia Pakistan China Nepal Japan Phili J 1 Taiwa S Ma Australia India T India Pakistan gascar India
140. or experimental data Mistaken calculations or measurements with quantifiable and predictable differences The probability that a flood will be greater than a set limit Extension of a relationship beyond the limits of observations Sudden and unexpected flooding caused by local heavy rainfall or rainfall in another area July 2006 Wallingford Introduction to flood hydrology river modelling and floodplain mapping Flood A temporary unwanted covering of land by water Flood damage Damage to receptors buildings infrastructure goods production and intangibles life cultural and ecological assets Flood forecasting system A system designed to provide a forecast of flood levels before they occur Flood frequency The probability expressed as a percentage that a flood of a given size will be equalled or exceeded in any given year A statistical expression or measure of the average time period between floods equalling or exceeding a given magnitude See Return Period Flood hazard map A map with the predicted or documented extent of flooding with or without an indication of the flood probability Flood level Water level during a flood Floodplain Area of land adjacent to a river estuary or coast which is subject to inundation by flooding Flood risk Flood risk is defined as Probability of flooding x Consequence of flooding Flood risk is normally measured in terms of economic damages for a particular pr
141. ormulae e Suspended load formulae e Total load formulae Recommended use Ackers White total load formula a aan Improved practices 1 Understand morphological diversity Undertake geomorphological assessment Retain morphological diversity Minimal reduction in channel properties Minimum disruption to bed and banks during and after construction a HR anil Improved practices 2 e Preserve pool and riffle sequences where possible Examine susceptibility of upstream channel to morphological change Avoid creating very deep pools Avoid over widening Avoid artificial liners Set back embankments 11 Av rn vane Mitigation enhancement restoration techniques In stream devices e g deflectors low weirs Reinstate substrate Reinstate meanders if appropriate Create non uniform channels Promote bank stability with tree and bush planting Plan careful management and maintenance 12 Exercise Impact of river works on the morphology and sediments of the river channel Ge irwan General information At the position shown in the catchment Figure 1 a reach of the river was straightened and widened for flood defence purposes A flood embankment was placed adjacent to the river on the left bank to protect property and on the right bank set back 100m on the flood plain to protect arable farm land This work was undertaken twenty years previously Dredging has been undertaken twice within the twenty
142. orologic model 1 Add the Apia and upstream catchment total rainfall amounts to the meteorologic model Select the Precipitation Gages element in the Watershed Explorer to open the Total Storm Gages editor This element should be located one level 10 under the meteorologic model Enter Apia for the Gage Name and 150 for the Total Depth Add the Upstream gauge total rainfall in the same way note the total rainfall for this gauge is 250 mm Total Storm Gages Gage Meme Figure 15 Apia and upstream Total Storm Gages 2 Inthe Watershed Explorer click the plus sign next to the Subbasin 1 element and select the Gage Weights sub component see Figure 16 A Component Editor will open with two tabs Gage Selections and Gage Weights Depth and time weights are required for all precipitation gauges with the Use Gage option set to Yes For this example the Vasigano East gauge will be used for all subbasin elements because it contains the storm pattern the other gauges only contain total storm depths Once the correct precipitation gauges are included for Subbasin 1 select the Gage Weights tab and enter the correct Depth Weight from Table 5 for Subbbasin 1 The Time Weight will be 1 0 for the Vasigano East gauge in all the subbasins see Figure 17 Complete this step for the remaining subbasins Figure 16 Apia and upstream Total Storm Gages 11 Figure 17 Gauge weight
143. pen from your previous work re open it When you have re opened it go to the File menu on the main window and select Save Project As In the Title box enter Example 2 Steady Flow with bridge added and in the File Name box enter Example_2 pry Note it is important that you check under the Options menu that the Unit System is set to SI e Standard International or metric units The purpose of this exercise is to add a bridge to the steady flow that you set up in Exercise 1 A proposed bridge is to be located just downstream of the cross section with the Station Label 1 6 The first step is to select the Geometric Data from the Edit menu on the HEC RAS main menu Once this option is selected the geometric data window will appear as shown in Figure 1 Edit and or creale cross sections KIBR Fie Edit Wew Tables Took Help SEGL anot Fa I J z Ta wiz Pump Saton en Hb Paari View Lt f tee O aki Figure 1 Geometric data window The proposed bridge is to be located 30 m downstream of the cross section labelled 1 6 The first set is to add an additional cross section to your model and alter their properties according Open the Excel spreadsheet called HEC RAS Example data xls There is a Worksheet entitled Bridge Data This includes all the additional data that you will need to add the proposed bridge to your model To enter an additional cross section data press the Cross Section butto
144. per provided as follows i Rank the flows in descending order starting with the highest and finishing with the lowest Give a ranking number m to each flood flow The largest flow will be ranked 1 and the smallest ranked 16 Estimate the return period T of each flood flow using the equation T n 1 m Note in this case n 16 Plot the flood flows on graph paper 1 Plot flood flows on the y axis and return period in years on the x axis s HR Wallingford Working with water Ge vn waning se The problem continued x Draw a straight line through the points and estimate the 1 in 100 year flood flow from the graph Plot the flood flows on graph paper 2 Flood flows on the y axis and return period in years on the x axis Draw a straight line through the points and estimate the 1 in 100 year flood flow from the graph What is the difference between your two estimates of the 1 in 100 year flow using the different types of graph paper ae HR Wallingford The problem continued ix x Which estimate do you think is correct The equation below gives an estimate of the maximum flood Q flow for a catchment with an area of A km What is the maximum flood that could be generated by the catchment Q 100A How does this compare with your 1 in 100 flood flow estimates a HRwvaling 1 in 100 year flood flow estimation Flood flow Return period T m s years T n 1 m Data
145. predicted hydrgraph 1200 VP D predicted hydrograph two 90 190 Time hrs M Flow routing Benefits limited data requirements quick and cheap to use Limitations no water levels except reservoirs not suitable for flow reversal looped systems and tidal systems GU veg Hydrological design Design storm depends on upstream characteristics especially area A single design storm to the outfall will not give design flows at all points across catchment Critical duration of design storm will be shorter in upper catchment than lower catchment Iterative process to get best compromise HR Wallingford Working with water 4 A allin ce Detailed river models Predicts flows and water levels Uses e Design of new works for example flood defences channel improvements structures Impact of new works _ i Panna D tailed river models continued Uses continued Operation of structures e g gates Producing flood maps Reconstruction of past floods Contingency planning Real time flood forecasting Fluvial tidal interaction AV rwm River modelling Hydrodynamics Steady or unsteady flow Require detailed topographic survey Many available packages Widespread use of implicit numerical methods to ensure robustness Too easy to use Vie Wallingford Working with water GU He vance Detailed computational river models e Many standard comme
146. project Create a New Project Name Description Location d iwork Samoa Test_HMS Ga Default Unit System Metric Cancel Prvan Input data manager HR Wallingford Wor Qing with water HR Walling Creating a basin mod He w Gua Few Comte Bente D g2 A ere Aa L lt J Venger NOTE aX Conert NOTE O HR Walling Fie EGR View Comgorerts Parameters Congue Mesuts Toot Global Summary Results for Run Run 17 Project Vesgano Srmutation An Mun 1 Sat of Pun 1 10 00 Baar Modet aro t fra ot Ruri OJjan2001 1230 Meteorologic Modet Gauge weights Compute Tree m2006 164 00 03 Control Spectticntions xw 2001 vime Unite sooo o Myra Drainage Ares Pest Discharge Newent oon ans fact tower PO Oet Reach m An Ao Gs States Sre React Comporerts Compute Besut 7 Subbesr t Marne Run 1 tas Cetergton Danno condones January 20 Subbacr Basin Modet Vesqano 1 Meter kapa Modet Gouge mert Control Specticaions Jar2001 J gma roading t uritatie wih the gren parameters VARNES Error n routing tor Rosch 2 Marg rolling 2 unisti wth the gren parameter NOTE 10185 Frished computing simson run Fun 1 at tee NAO HR Wallington Summary of results graphs Fie Edt View Components Oe aam TJ Venigare jan sets 3 vasgwo 1 Jurcdon Eimert Outer Resuts for Run Ruri 1 OP ran wwen A Graph for Junction Outlet
147. ptions Figure 5 Unsteady Flow Analysis Simulation Window Once the model has finished all of the computations successfully you can begin viewing the results Several output options are available from the View menu bar on the HEC RAS main window including Create section plots Profile plots General plots Rating curves X Y Z perspective plots Detailed tabular output at specific cross section cross section table Limited tabular output at many cross sections Let s start by looking at Stage and Flow hydrographs Go to the View menu and select Stage and Flow Hydrographs Investigate the shape of the various water level and flow hydrographs for the different cross sections When you have done this go to the View menu and select Water Surface Profiles Click on the black arrow and you will see an animation of how the water surface changes with time Next look at an X Y Z Perspective Plot of the river system From the View menu bar on the HEC RAS main menu select X Y Z Perspective Plots A multiple cross section perspective should appear on the screen Try rotating the perspective view in different directions Now press the black arrow and you should see an animation of how the water surface changes with time Now look at the tabular output Go to the View menu bar on the HEC RAS main window There are two types of table available a detailed output table and a profile summary table Select Detailed Output Tables to get
148. r or floodwalls pumping station Flood banks Simple and effective Pumping or storage required for runoff from defended area Limited design standard e g 100 years then overtop or fail Often visually intrusive May cause raised upstream levels backwater effect May cause raised downstream levels loss of storage Ge rn wang Flood banks Design considerations e Location and dimensions Geology soils hydrogeology Bank stability Seepage Bank protection and access Future modifications to design lt a a HR Wallingford PA Floodwalls Take limited space Design for hydrostatic loading freeboard Reinforced concrete or sheet piles Impervious curtain to prevent seepage underneath Face with brick or stone aggregate finish Minimum height for public safety In association with temporary defences a HR Wallingford Developed area Channels enlarged Ge unwangaq un Channel improvements Increase conveyance capacity Increase cross sectional area Reduce roughness Remove bends Increase water surface slope 2 3 stage channels Ge ve wage Channel improvements Issues problems e Decreased depths Increased flow velocities Potential siltation at low flows Dredging may be ongoing Potential morphological re adjustment Environmental impact and disturbance GU rn vege Reducing roughness e Clear banks of dead or overhanging trees e Seasonal reed and weed removal
149. rcial packages have one dimensional hydraulics e Steady flow prediction of water surface profiles use for short lengths of river attenuation small Detailed computational river A AN lingford allingfo models Unsteady flow e Prediction of water level hydrographs e Longer lengths of river attenuation or storage important e Other unsteady effects tides flood storage gate movement etc a rv River modelling software packages CARIMA SOGREAH FLDWAV US NWS ISIS HR Wallingford HEC RAS US Army of Engineers MIKE11 DHI SOBEK Delft Hydraulics HR Wallingford Working with water Ni ee River modelling two dimensional modelling Based on shallow water theory Need irregular grids to fit natural topography Finite element models available commercially Computationally intensive Feasible to use in practice a Hawai Two dimensional modelling Channel and floodplain mesh APs Two dimensional modelling Velocity vector details R Wallingford Working with water Detailed physical models Three dimensional hydraulics Examine complex flow patterns Sites where one dimensional hydraulics inappropriate Sites where accurate prediction essential Avoid scale effects Detailed physical models Laboratory scale model Short lengths of river complex geometry Hydraulic design of structures Typical scales Flood plain models 1 50 to 1
150. rd Working with water Ge vn waning se n Hydrological modelling l Nature of a flood producing system is complex interaction of atmosphere land geology vegetation geomorphology soils activities of mankind a HR Wallingford a Therefo re Modelling can only provide generalised estimates Local information on observed floods is essential to calibrate models Best information on future flood magnitudes is obtained from historical records i e measured flood flows aswa Typical maximum observed flood flows in the South Pacific Country Catchment Maximum Discharge area observed per unit area km flood flow m s km m s Molokai 12 762 63 5 Kauai 58 2470 42 6 Tahiti 78 2200 28 2 Fiji 6139 59 0 Fiji 996 7 8 Fiji 559 34 9 Fiji 447 5 6 American Samoa 14 5 4 Samoa we HR Wallingford Working with water Ni as Typical maximum observec Maximum observed flows m s floods in the South Pacific 60 80 Catchment area km2 Ni Typical maximum observec floods in the world Plot of discharge Q against catchment area A for the world s maximum floods v m E w o 9 ke im Q s a Catchment area A km Ae Hn anger Typical maximum observec floods in the South Pacific For regions of the world such as the South Pacific that have intense rainfall a very approximate estimate of th
151. rns to the atmosphere through evaporation and transpiration However during a storm event this evaporation and transpiration is limited Depending upon the soil type ground cover antecedent moisture and other properties a portion may infiltrate and move horizontally as interflow just beneath the surface or percolate vertically to the groundwater aquifer beneath the catchment The interflow moves into the stream channel Water in the aquifer moves slowly but eventually some returns to the channels as baseflow Water that does not pond or infiltrate moves by overland flow to a stream channel The stream channel is the combination point for the overland flow the precipitation that falls directly on water bodies in the catchment and the interflow and baseflow Ni u Runoff process Evapotranspiration t s Transpiration Evaporation IE Yz WA Interception Evaporation sts soil litter Direct throughfall Gr Rar A yy Satu k AST P ive as Vasa anan ed area se Verlang flow 7s HR Wallingford Working with water Piian Runoff process in HEC HMS Evapo transpiration Land surface infiltration Water body overland flow 3 amp interflow Stream channel baseflow Groundwater aquifer Stream discharge Exercises Vie Wallingford Working with water Na Wallingfo a Precipitation and runoff exercises a Exercise 1 If a total rainfall amount of
152. ross sections Log Log fitting by eye or with software Several equations each for a range of level or change in channel shape through time Rating curves Typical example a HR Wallingford Discharge Q 3 Vie Wallingford Working with water Rating curves a HR Wallingford Reason for loop Water surface at t Rating curves a HR Wallingford Adjustment for looped rating Adjust observations for rising or falling stage during measurement Measured discharge exceeds normal flow on rising flood stage Discharge is less than normal flow on falling flood stage Biggest impacts for rapidly varying out of bank flows and wide flood plains Rating curves Practical difficulties Extrapolation above the highest gauging Backwater from a downstream control Bypass flow under flood conditions a HR Wallingford Out of bank section geometry Seasonal changes growth and decay of vegetation Morphological effects mobile bed alluvial friction f mE HR Wallingford Working with water av ae Rating curves No data for high flows Discharge Ge rwn Rating curves Backwater influence Discharge aP nna Rating curves Backwater length Normal depth Mo curve we Vie Wallingfor Working with water Ge rn wang Rating curves Seasonal influence Level A Rainy season gauging Dry season gauging Discharge
153. rs that affect the shape of stage versus discharge curves Understand the practical difficulties of estimating flows from stage versus discharge curves Understand the uses of stage discharge curves a HR Walingfor Skills acquired To be able to plot a stage versus rating curve To be able to extrapolate a stage versus rating curve to estimate high flows T HR Wallingford Working with water av iu Flow gauging station Satellite or radio Gauge house __ transmitter _ Stage reading and River and well recording equipment levels are the same Si l Inlet pipes a ae Flow gauging station hee T gt 4 as N D Stage m above datum N foe N P Discharge m s m Vie Wallingford Working with water Rating curves Derive information from data Relate river level or depth to discharge a HR Wallingford Unique or looped curves where slope of river is less than 0 4 m km Allow data validation by checking latest measurements against earlier ones Care needed when there is a change of hydraulic condition e g out of bank flow Allows for extrapolation above the highest recorded flow Gen veneer Rating curves Typical rating equations General form of rating over a range of level Q a h b c Coefficient b represents a local datum Coefficient c has some theoretical values for structures and simple c
154. s I Click the River Reach button on the geometric data window A Move the mouse pointer over to the drawing area and place the pointer at the location where you would like to start drawing the river reach 3 Press the left mouse button once to start drawing the reach Move the mouse pointer and continue to press the left mouse buttons to add additional points to the line segment To end the drawing of the reach double click the mouse button and the last button of the reach will be placed at the current mouse pointer location All reaches must be drawn from an upstream to a downstream direction 4 Once the reach is drawn the interface will prompt you to enter an identifier for the River name and the Reach name In this example the River name should be entered as Main River and the Reach name as Upper Geometric Data File Edit View Tables Tools mam uuu ee ee ee m m sm mu w mw wuaumwun unn m Figure 4 Geometric data window with Main River reach drawn The next step is to enter cross section data This is done by pressing the Cross Section button on the Geometric Data window shown in Figure 4 Once this button is pressed the Cross Section Data Editor will appear as shown in Figure 5 Cross Section Data es No Data for Plot Figure 5 Cross Section Data Editor All the data you need is Included in various Worksheets in an Excel spreadsheet called HEC RAS Example _ data xls To enter the cros
155. s Robustness and resilience of the design Reversibility of the option Adaptation for future change Key components of uncertainty in practice a HR Wallingford Hydrological design estimates River roughness estimates Inadequacies inconsistencies uncertainties in historical data Structure blockage assumptions Other components of uncertainty in practice a HR Wallingford Uncertainties in formulae and calculations Impact of climate change e g sea level rise Trends and cycles e g land tilt Changes in land use e g urbanisation of the catchment f Vie Wallingford Working with water GU ornan Hydrological uncertainty Arises from statistical uncertainty Factor of about 2 on discharge for no data equations Possibly 20 uncertainty on 1 in 100 year flood flow with say 30 years data Possibly best to use return period as free parameter Quote a range e g 70 to 140 years instead of 100 years GP irnn River modelling accuracy Hydrological Uncertainty e usually the largest component Flow to level correlation e several factors from the modelling process Level to flood limit correlation e can be improved by better local survey One dimensional river Ax Wallingford Coe modelling accuracy Survey uncertainties Roughness uncertainty Approximations in numerical methods Calibration quality Extrapolation above calibration flows Vie Wall
156. s for Subbasin 2 Define the control specifications Create the control specifications by selecting Components Control Specifications Manager menu item In the Control Specifications Manager window click the New button and enter Jan2001 for the Name and 10 January 2001 for the Description In the Component Editor enter 10Jan2001 for both the Start Date and the End Date Enter 10 00 for the Start Time and 15 00 for the End Time Select a time interval of 5 minutes from the Time Interval drop down list see Figure 18 fi Control Speciications orc 10 January 2001 tl eg Start Dabe dd Lh Start Tie tm 10600 End Date savy an I End Ts Horm 15 00 Tine kerrat 5 Minutes Figure 18 Entering control specifications data Create and compute a simulation run Create a simulation run by selecting the Compute Create Simulation Run menu item Keep the default name Run 1 Select the Vasigano 1 basin model Gauge weights meteorologic model and Jan2001 control specification using the wizard After the wizard closes select the Compute tab of the Watershed Explorer Select the Simulation Runs folder so that the Watershed Explorer expands to show Run 1 12 Click on Run 1 to open the Component Editor for the simulation run Change the description for this simulation run by entering Existing conditions 10 January 2001 storm see Figure 19
157. s in the Watershed Explorer or in the basin model map Change the percentage impervious area to 15 for each of the three subbasins Update the Gauge weights meteorologic model to include the subbasins from the Vaisigano 2 basin model Select the meteorologic model in the Watershed Explorer to open the Component Editor Open the Basins tab and change the Include Subbasins option to Yes for the Vaisigano 2 basin model Urbanised simulation run Create a new simulation run for the future conditions basin by selecting the Compute Create Simulation Run menu item Keep the default name of Run 2 and select the Vaisigano 2 basin model the Gauge weights meteorologic model and the Jan2001 control specifications using the wizard Open the Component Editor for Run 2 and enter Urbanised conditions 10 Jan 2001 storm as the description Compute Run 2 and compare the peak discharges for the urbanised conditions with the existing conditions at the Outlet Results from the two simulations can also be compared from the Results tab of the Watershed Explorer Results are available as long as no modifications have been made to components used by the simulation run For example 1f a constant loss parameter was changed in a subbasin element then the results for all simulation runs in which the subbasin element resides will not be available It is easy to determine if results are available If the simulation run icon is grey then results ar
158. s section data do the following I Open the HEC_RAS_Example_data xls spreadsheet In the Main River Cross section data Worksheet you will find all the data you need In the Cross Section Editor window shown in Figure 5 go to the Options window and Add a new Cross section An input box will appear to prompt you to enter a River Station Identifier This must have a numeric value This numeric value describes where each cross section is located relative to each other within a reach Cross sections are located from upstream the river station with the highest numeric value to downstream the lowest river station In the spreadsheet the River Stations are number 1 9 to 1 1 Enter the upstream cross section first River Station 1 9 as shown in Figure 6 Cross Section Data Plot Options G GBI I Keep Prev XS Plots Clear Prev I in jarmu ha Ha Example 1 Steady flow Plan 06 os gt f 035 Elevation rm Wwe T 50 100 150 200 20 30 350 400 Stalin eri Figure 6 Cross section data entered for River Station 1 9 3 Once all the data has been entered press the Apply Data button This button is used to tell the interface that you want the data to be accepted into memory This button does not save the data to the hard disk This can only be done from the File menu on the Geometric Data Window Plot the cross section to visually inspect the data This is done by pressing the
159. s sections River Trent at Drakelow PH 6 12 95 liine gt Bankfull hydraulic and geometric characteristics 3 2 86 Manning s n roughness coefficient Discharge Water surface slope 0 000437 1 2288 Average cross sectional area 142 5 m Average flow width 54 m Average hydraulic radius 2 62 m Description of channel Bed material unknown Left bank grass with horse chestnut trees at downstream limit of reach Right bank with horse chestnut and beech trees Left flood plain is a golf course with occasional oak yew hawthorn horse chestnut and poplar tree coppice Right bank formed by steep wooded bank lowering to flood plain at downstream limit with beech and chestnut trees with bank grass undergrowth a Plan Description of channel Meander Bed material unknown Bank lining variable concrete wall boat moorings willow hawthorne ash sycamore holly alder and horse chestnut with undergrowth of nettles and bramble Left flood plain parkland with mature elm trees gardens with fences rough asture ight flood plain is parkland with mature elms and limes market gardening Evesham Water level 30 1 86 Cross sections ZRECERRES ERIS WRENS SSS Sore SS QATA RIES sss ways NAG SR RSS SE SR RSS SENS zs ENN SESS SAKA RON SSH SSNS ENA ah SESSA SSS SSSSSSSS SPSS NN SSS SSAA SSS SORIA SEARS Shy a XA SR ee ONS RAR Sooty ANANA RS SAGO TENS A SASSER BAR SS SSS SS SSS SSRs Se AN SESE FANA
160. s the stage Plot this curve on the graph paper up to a stage h of 3 3 m Use your graph to estimate the flow when the stage is 3 2 m How accurate do you think your estimate of the flow at a stage of 3 2 m is Data for rating curve exercise Exercise sheet Discharge m s Q 0 0168 h 0 0424 4 O9L OSL OVI OEL Oc OLL s w BieuS3sidq OOL 06 09 QZ 09 OS OV Oe OC Ol VC SC 9 Le 9 O gt N cO Le CE wi ebe s Vie Wallingford Working with water Na Wallingfo a Overview of flood flow estimation GY sn wang Learning objectives Appreciate expected values of flood flows for the South Pacific Understand statistical methods to estimate the design flood Appreciate the uncertainty in estimating rare floods with limited data a HR Wallingford Skills acquired To be able to estimate the 1 in 100 year return period using annual maximum flow data To be able to estimate the probability of a flood of given probability occurring within a certain period of time HR Wallingfo
161. ss 10 mm Constant rate 2 mm hr Impervious 5 Initial loss 10 mm Constant rate 2 mm hr Impervious 0 Initial loss 10 mm Constant rate 2 mm hr Impervious 15 Initial loss 10 mm Constant rate 2 mm hr Impervious 20 Table 2 Subbasin details continued Subbasin Loss 2 Subbasin Channel number Downstream Junction 1 Area 4 978 km Loss method Initial and constant Transform method Kinematic wave Baseflow method none Downstream Junction Area 4 231 km Loss method Initial and constant Transform method Kinematic wave Baseflow method none Downstream Junction 2 Area 5 607 km Loss method Initial and constant Transform method Kinematic wave Baseflow method none Downstream Junction 2 Area 1 772 km Loss method Initial and constant Transform method Kinematic wave Baseflow method none Downstream Junction 4 Area 0 724 km Loss method Initial and constant Transform method Kinematic wave Baseflow method none Downstream Junction 3 Area 2 009 km Loss method Initial and constant Transform method Kinematic wave Baseflow method none Route upstream No Routing method Kinematic wave Length 3634 Slope 0 07 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 20 Side slope 5 Route upstream Yes Routing method Kinematic wave Length 4711 Slope 0 045 Subreaches 5
162. sts from the Ministry of Natural Resources Environment and Meteorology to produce flood hazard maps of the Vaisigano River in Apia During the first of two visits by the flood modelling specialist of HR Wallingford special emphasis was given on providing baseline knowledge in flood hydrology river modelling and floodplain mapping An introduction in two widely used flood modelling freeware packages was provided enabling the course participants to set up a simple computer model of the Vaisigano River During the next visit in November 2006 the model will be developed further to produce flood hazard maps and flood risk estimates as basis for the development of flood mitigation options and flood management guidelines Improving flood prediction and water resource management requires long term sustainable investment not only in improving and maintaining the hydro meteorological network but also in increasing the capacity of the MNREM s Hydrology and Meteorology Division not only in data collection but also in data maintenance quality control and analysis The extensive training material provided to the course participants forms part of this report in appendices E to G Details on the technical findings and the river cross section survey are provided in separate reports EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States Samoa Capacity Building in Flood Risk Management Vaisigano Riv
163. t J ajujsi ioj wJ alae s 1 Jol By Am Ar sim ppur etc Oo z m m ga ene mas U M UMAPI TTE mars i aa MASI WPe ee eee sae Vakt V Tutuila American Samoa Riverine Flooding Hazard Areas SY ie aa I s r L i Day 4 Vie A Working with water ae Wallingford g Risk uncertainty and error GY en wang Learning objective To understand the difference between hazard and risk To understand the difference between uncertainty and error a HR Wallingford Skilled acquired To be able to assess the uncertainty in river model results To understand conceptual risk models used in flood management a HR Wallingford Working with water Pirwan What is a hazard A hazard is a physical event phenomenon or human activity with the potential to result in harm A hazard does not necessarily lead to harm GU irwan puampie of a flood hazard map Cr owmars 1 in 100 year flood extent fi eng 1 annual prubabilily nf arcurrence 3 1 es N Ti Wh hi te I in 1000 year flood extent 0 1 annual probability of occurrence r R Ck allege Viondewell GY revenge What is risk Risk in its simplest form has two components the probability that an event will occur and the impact or consequences associated with that event Risk Probability x Consequence HR Wallingford Working
164. tables are designed to provide specific Information at hydraulic structures e g bridges and culverts while others provide generic Information at all cross sections From the View menu select the Profile Summary Table option Open a new Excel spreadsheet file From the File menu in the Profile Output Table window select the Copy to Clipboard Data and Headings option In the Excel spreadsheet you have opened select the paste options and save the spreadsheet as Example 2 results xls Compare the maximum water levels from Exercise without the bridge to those that you get from Exercise 2 with the bridge in place What is the difference in maximum water levels directly upstream of the bridge for the 1 in 100 year flood between the existing situation and when the proposed bridge is in place You have now completed the second example Exercise 3 Running an unsteady flow model with the proposed bridge in place If the Example_2 project is not still open from your previous work re open it When you have re opened it go to the File menu on the main window and select Save Project As In the Title box enter Example 3 Unsteady flow with bridge and in the File Name box enter Example_3 prj Note it is important that you check under the Options menu that the Unit System is set to SI i e Standard International or metric units The purpose of this exercise is to run the previous model you created with the proposed bridge with an unsteady flow i
165. the File New menu item Enter Vaisigano for the project Name and Vaisigano land use change study for the description as shown in Figure 2 below Project files will be stored in a directory called Vasigano a subdirectory of C Hmsproj Set the default unit system to Met ric and click the create button to create the project Creale a New Project Decipher Vertaa larvi uch change paf Lonation dl hvrorkihechmspno z Derlnud Und System Metric ie Figure 2 Enter the name description and default unit system of the new project Set the project options before creating the gages or model components as shown in Figure 3 Select the Tools Project Options menu item Set Loss to Initial and Constant Transform to Snyder Unit Hydrograph Baseflow to Recession Routing to Muskingum Precipitation to Gage Weights Evapotranspiration to None and Snowmelt to None Click the OK button and close the Project Options window Project Options Vaisipano Loss iniiai and Constant Transform Snyder Unit Hydrograph w Routing Evapotranspiraliorc 4 Figure 3 Enter the project options Input data Create a precipitation gage for the Vaisigano East data Select the Components Time Series Data Manager menu item Make sure the Data Type 1s set to Precipitation Gages Click the New button in the Time Series Data Manager window In the Create A New Precipit
166. the first table to appear This table shows detailed hydraulic information at a single cross sections Now bring up the profile summary table This table shows a limited number of hydraulic variables for several cross sections There are several types of profile tables listed under the Std Tables menu bar of the profile table window Some of the tables are designed to provide specific information at hydraulic structures e g bridges and culverts while others provide generic information at all cross sections From the View menu select the Profile Summary Table option make sure you select the maximum water surface elevation Open a new Excel spreadsheet file From the File menu in the Profile Output Table window select the Copy to Clipboard Data and Headings option In the Excel spreadsheet you have opened select the paste options and save the spreadsheet as Example_5_results xls Compare the maximum water levels from Exercise 4 running with an unsteady flow with no sediment to those that you get from Exercise 5 with an unsteady flow hydrograph and sediment What is the difference in maximum water levels directly with and without the weir in place You have now completed the fifth example APPENDIX G Glossary of Terms EU SOPAC Project Report 69d Lumbroso amp others Appendix G Glossary of Terms Introduction to flood hydrology river modelling and floodplain mapping Accuracy Bankfull capacity Basin river Calibration
167. the river upstream of the barrier site Figure 5 Photograph of a barrier similar to that which is propose Estimated Proposed 1 in 100 year location of flood extent barrier Mouth of for the city of oe 0 000 the river opulation is l with the sea River Sarawak Slope of river 1 3000 x Figure 3 General location map for the River Sarawak 7x N eee N 4 W x g ky H 4 BOM VANES I A 7 amp 1 f Figure 4 Photograph of the river upstream of the barrier site Figure 6 Picture of a barrier similar to that which is proposed Case 3 Proposed bypass channel for the city of Brechin in New Zealand A bypass channel is proposed on a river in New Zealand to reduce flooding in the city of Brechin The location of the bypass channel is shown in Figure 7 The local government requires that there should be no increase in flood levels The river has a slope of 1 in 1 000 A study was needed to assess the impact of the proposed design on flood levels and develop a scheme which will not raise flood levels The bankfull capacity of the river channel through Brechin has been estimated to be 200 m s Calibration data were available for an event which occurred in 1991 which had a flow of 550 m s and an approximate return period of 1 in 100 years w Route of flood K 9 AD bypass channel Y X se SL SAP 15 AL AN lie S r P e E Er P Ss a and po AS APEA v Za S TO ip Stan ER
168. thod Initial and constant Transform method Kinematic wave Baseflow method Recession Downstream Junction 8 Area 0 435km Loss method Initial and constant Transform method Kinematic wave Baseflow method Recession Routing method Kinematic wave Length 4353 Slope 0 044 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 30 Side slope 5 Route upstream Yes Routing method Kinematic wave Length 4590 Slope 0 039 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 25 Side slope 5 Route upstream Yes Routing method Kinematic wave Length 3650 Slope 0 028 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 50 Side slope 5 Route upstream No Routing method Kinematic wave Length 2770 Slope 0 020 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 60 Side slope 5 Route upstream Yes Routing method Kinematic wave Length 1600 Slope 0 0086 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 70 Side slope 5 Route upstream Yes Routing method Kinematic wave Length 961 Slope 0 0007 Subreaches 5 Shape Trapezoid Manning s n 0 05 Bottom width m 80 Side slope 5 There are six different Meteorologic models that have been set up In the HEC HMS model together with their relevant control specifications T
169. tion upstream boundary of butte ct J Ins Row Channel ROB 500 a Hiwa ll Cross section conventions Ba GB Reco Prevx Pits Clea Prev Multiple Reach Date Set Pian Exe Existing Conditions vectrean Left bank Right bank Flow direction aoe into paper a r g iiyji gt FD Bermat cross section data Station x axis Elevation y axis 20 21 19 15 15 Left bank 22 Need to add the distance known as the Reach length between each cross section a HR Wallingford Working with water a HR Cross section interpolation Upstream Section Right Bank Interpolated Section Downstream Section Ge rwng Cross section sub division for conveyance calculation Kio Ki K2 Krob K3 Ge rwng Orientation of cross sections R Wallingford Working with water 3 24 1998 Cross Section 3 J i E Left Ineffective Flow Station A Station ft Geometry is newer than output 822 32 1821 16 Example 1 Existing Conditions 3 24 1998 Cross Section 10 aan aa 4 Left Levee Ground Station Eja Levee Bank Sta 600 800 Station ft Cross Section Warning Geometry is newer than output River SE EE 3613416003 C S Reoch Upper Reach River Sta B J Critical Creek Example 1 Existing Conditions 3 24 1998 Cross Section 8 1 k 1 J WS 100 yt ideti aaah LS Ground Bank Sta lew ation It
170. ulation uniform flow conveyance and flow resistance Typical water surface profiles for various conditions a HR Walingfor d Skills acquired To be able to understand different hydraulic terminology To be able to use simple hydraulic equations HR Wallingford Working with water GY re venga What is hydraulics Study of how water moves Deterministic based on mass conservation and force balance Uses principles of momentum and energy transfer Provides water levels velocities flow rates a HR Walingford Links to other areas Water resources e What are water levels for different flows in different seasons River morphology sediment carrying capacity Water quality e velocities associated with flows and channel shapes and sizes GY in ving Open channel principles Energy and Momentum Uniform flow e Channel conveyance e Resistance equations States of flow Water surface profiles AV HR Walon Working with water AV Hn sang Energy and Momentum Energy is the capacity to do work Kinetic energy from speed Potential energy from position Also heat sound etc Each type has a magnitude value only Energy balance on streamlines Total Energy is conserved Energy losses arise because some energy types are ignored in analysis Page 7 AView Energy and Momentum Momentum is mass times velocity e Changed by forces and impuls
171. ural reach Ge ve waning se Straightened channel Modified bed level Upstream Upstream erosion and downstream deposition in a straightened channel GU irwan Physical impacts enlargec channels e Reduces unit stream power and causes sediment deposition Over widened channels reduce flow velocity Sediment deposition likely to result in channel returning to original equilibrium Sediment deposition occurs forming permanent morphological features Maintenance regime required to maintain arged channel GP rwng Physical impacts embankments e Larger flows are confined e Greater velocities associated with larger flows may affect channel morphology Ge rwng Physical impacts clearance of vegetation e Trees and bushes stabilise banks their removal can result in bank erosion e Emergent vegetation stabilises banks and creates berms and ledges removal can result in erosion and channel widening Ge waning Sediment transport Assessing sediment load is a vital part of understanding river behaviour e Bed load moves on or near the bed e Suspended load carried in suspension e Total load sum of bed and suspended loads e Wash load finest portion of load silt and clay permanently in suspension Wash load is supply limited and is washed through the system Sediment load ts key determinant of the stable river Na a Prediction of sediment load Many formulae of three main types e Bed load f
172. ures available Understand the effects of these changes Ge ve wang Skills acquired To be able to make an informed assessment of the different flood mitigation measures available for a particular site a ss oem Methods of flood defence Flood alleviation structural measures e Hazard is reduced but not eliminated e High capital and maintenance cost Development control non structural e Land use planning in flood risk areas e May be difficult politically Flood warning non structural e Loss of life reduced e Small reduction in other losses ae HR Wallingford Structural measures Aims Reduce flood levels Reduce flood flows Reduce flood impact Solutions Flood banks and walls Channel works Flood storage on off line Flood relief channels Tidal flood barrier Pumping Redevelopment Ne us Choice of flood defence option Constraints Topography and land availability Cost Planning considerations Design standards Public views e Environmental issues Possibilities e Combination of options e g walls and warning Temporary defences _ a HR Non structural measures i e do not change the river hydraulics e Flood forecasting and warning Planning and building control Building restrictions Retrofit runoff control Flood proofing Flood insurance last resort Possible secondary floodwalls or embankments Developed area Flood limit Flood embankments Sluice o
173. urs Time base T m amp HR Wallingford Working with water Y HaWalingS Factors affecting flood hydrograph Shape of the catchment This affects the time water takes to reach the outlet Size of the catchment in terms of area A Size of the flood is often related to A Slope of the channel Drainage density Higher the drainage density the shorter the time to peak Land use Climatic factors Zuna Degree of urbanisation HR Wallingford Working with water Z swas Attenuation from lakes and reservoirs What do you expect the characteristics of a flood hydrograph for the Vasigano catchment to be like Vie Wallingford Working with water awas Unit hydrograph UH theory Unit hydrograph UH is the rapid response of the catchment to unit depth of effective rainfall falling in unit time The concept makes three main assumptions Time invariance unique and constant rainfall runoff relationship e Linearity increase in rainfall causes proportional increase in runoff e Superposition total runoff is sum of individual runoff hydrographs Pirwan Hydrograph computation 1 Construct unit hydrograph a HR Wallingford Unit hyd rog raph TiaG Fina i v mM co o lt Q A m Time hours Pn Wallingford Working with water E a Estimating Tp From empirical equat
174. who wrote EU SOPAC Project Report 69d Lumbroso amp others EU EDF SOPAC Reducing Vulnerability of Pacific ACP States Samoa Capacity Building in Flood Risk Management Vaisigano River Apia 8 Overall the training was an eye opener for me was able to learn more stuff that would enhance my duties at work The lecture material as well as the exercises were well prepared and easy to understand The exercises were a good form of practice putting the theory aspects to work The majority of the participants indicated that in future they would like more training in the use of the hydrological modelling software HEC HMS and the hydraulic modelling software HEC RAS 6 OUTLOOK The training in the use of these software packages will be continued during second visit of the HR Wallingford SOPAC team which is likely to take place in November 2006 This training will not be as formalised as during the first visit The training will take the form of the completion of a hydraulic model of around 2 km of the Vaisigano River This model will be constructed calibrated using available data on historical floods and then used to estimate design flood levels for the Vaisigano in the vicinity of Apia by each of the participants Flood maps will also be produced and flood risk either in terms of direct economic damage or injuries to people will be estimated Further flood mitigation options will be evaluated and flood management guidelines will
175. with water a HR Wal BURNHAM ON SEA US 5 000 to US 5 000 US 1 Page 7 j P A Bae Cinmel ogt 25 77 O Z Fo Kinmel Bay A e a j GO Mort ffihuddian ase P m 7 HG Cottage 5 r A ERRA a ea NE F 2 2 Pen y ffordd Percentage of people with injuries ow tot B 55 tos B 10 to 25 1 to 2 5 C 5 to 10 O 25 to 50 EPn Conceptual risk model Source Rainfall river flow storm surge Pathway Bank failure flood plain flow sewer surcharging Receptor Property people possessions environment Consequence Damages distress disease death degradation v HR Wallingford Working with water A Wallingford ss Acceptability of risk Frequency F versus Impact curve N Frequency against impact number of casualties Three categories of significance Acceptable negligible Broadly acceptable Possibly unjustifiable As Low As Reasonably Practicable ALARP Unacceptable intolerable Intolerable Localtolefrability line Frequency F of N or more fatalities ALAR P Negligible Region 10 100 1000 Num ber of fatalities N AU rwng Perception of risk Individual risk Element of choice and personal control over the hazard Societal risk Imposed by others nature No personal control on acceptance Aversion to high impact consequence events
176. y ML K War abu top Uam move new Sof that God abane my Awd ak wade Vo Leche motorat aed n ul Lp WER ovr he pernas were wh Ard aor by understand The ereite were a good fem A prachee puthte the Leo Dopo te wore Ke only we alanas L Cheertd Woo the onu SHS aod jud Ce denh y b4 kand ro Ratsel R i QALA nA AARE Perat wolna divisiong go we had t Cpe we ISt aha veetes Just MLW Apter Boke inthe fibre w e shoud What areas of flood hydrology river modelling and flood risk manageme do you think should we edr aM AL k concenmirate on during the next raining and practical sessions i Oelober 20062 wa Pte Aala a F alt y A 4 1 i F loud MSE MUA ALAN lt la advourCle byte anig AN aa What other training in the fields of hyarology river modelling and water resources management would CANIS VON IN carrying OME yonr work more effectively Mere of AM We Alowo s a cestoal ude Woda La AL mo in Corp g 60 J AnH Lop Hor APPENDIX D Training Examination Questions EU SOPAC Project Report 69d Lumbroso amp others Appendix D Training Examination Questions 1 One of the most important input parameters for flood modelling is the flow What are the different ways to assess a design flow e g a 1 in 100 years flood and what do you think would be the most appropriate way to assess the design flood flow for the Vaisigano River catchment draining to Apia What are the main components of a flood hydrograp
177. ydrologic elements of HEC HMS Source used to introduce flow into the model Sink used to represent the outlet of a catchment Reservoir used to model the attenuation of a hydrograph caused by a reservoir or storage area Diversion used to flow leaving the main channel Ge rwng Subbasin and reach calculation methods Subbbasin Runoff volume Direct runoff using unit hydrograph techniques Baseflow Reach Routing methods including Muskingum Muskingum Cunge Lag Ge vn waning st Meteorologic model and control specifications component The meteorologic model component estimates the precipitation required by the subbasin element It can use various types of precipitation data e g gridded from radar gauges etc Control specifications component Sets the time span of the model run It includes a starting date and time an ending date and time and a computation step Fie E View Components Parameters Compute Renis DEBON a a h X w 4 S HR Wallingford Working with water User interface Toots Hep u s u Eu Component Componerts wp Rents Beem Hama Castro 1 Dement Hame Subbesin 2 Loss Method toi ons Cx Transtorme Method Snyder Unt Myarograph editor Corntort WARMING 10511 Spectied ime window cortona partal rtervals for gage Fire Dept End tise achusted to 1EJant 973 09 40 NOTE 10008 Fished opening prefect centro at ti
178. years The substrate of the river is gravel Tree and bush maintenance has been undertaken on the left bank and grass cutting on the right bank Figure 1 a HR Wallingford Describe the morphological problems which may be occurring in the river due to the flood defence works av HAW More specific information The sediment deposition is becoming a problem in reducing the channel flood capacity but ongoing dredging maintenance is too costly The ecological diversity of the channel is poor at low flows and there is little diversity on the right floodplain The previous alignment of the channel is shown in Figure 2 The land protected by the flood embankment on the right bank has been designated set aside land Figure 2 Previous route of river Set aside land 100m Sediment deposition a HR Wallingford Task gt Describe and discuss the possibilities for this channel to try and a maintain flood capacity b providing more sustainable morphological conditions c improve ecological diversity av HR Wallingford Methods of flood defence a ms Learning objectives Understand the different structural measures and non structural meas
179. you get from Exercise 4 with an unsteady flow hydrograph and sediment What is the difference in maximum water levels directly with and without sediment You have now completed the fourth example Exercise 5 Running an unsteady flow model with the proposed bridge in place an increase in the bed level caused by siltation and an inline weir If the Example_4 project is not still open from your previous work re open it When you have re opened it go to the File menu on the main window and select Save Project As In the Title box enter Example 5 1 in 100 year bridge sediment weir and in the File Name box enter Example 5 prj Note it is important that you check under the Options menu that the Unit System is set to SI 1 e Standard International or metric units The purpose of this exercise is to run the previous model you created with the proposed bridge with an unsteady flow an increase in the river bed caused by the deposition of sediment and a new weir that is to be built upstream of the bridge The first step is to go to the Edit menu in the HEC RAS Main Window and select the Geometric Data editor The Geometric Data editor shown should open In the Geometric Data editor go to the Tools in the menu and click on the Inline Structure button shown in Figure 1 A window similar to that shown in Figure 2 but without any data in it EER Edit and or creale cross sections File Edit Wew Taks Took Help hay k Fifi Cani

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