Pocket Guide - FLO
Contents
1. e The floodwave speed will be bound by a reasonable limiting Froude number e The model will run fast without numerical surging or over steepening of the floodwave 40 Guidelines Notes 41 Notes Making Flood Maps Mapper creates a diverse array of high resolution graphical plots including flood hazard maps including Ground surface elevation Maximum water surface elevation Maximum depth area of inundation Maximum velocity Final depth Final velocity Specific Energy Impact Pressure lt Static Pressure Levee freeboard deficiency Scour deposition and bed changes for the sediment transport option Manning N values Time to Peak Discharge dam and levee break Time to One Foot dam and levee break Time to Two Foot dam and levee break Temporally variable depth and velocity Flood hazard maps Shape files Some of the maps can be generated for floodplain channel and street flow Combined channel and floodplain maximum depth plots can also be generated Most of the maps can be displayed as either grid element plots line contour maps and shaded contour maps Shape files for importing results to GIS are automatically generated for most of the Mapper plots Some guidelines to consider when developing flood maps are 42 Flood Maps e The flood hazard map resolution is only as good as that of the topographic data base e Use background aerial images to enhance the f2. Pocket Guide PRO Model Contact Information General FLO 2D Software Inc P O Box 66 102 County Road 2315 Nutrioso AZ 85932 Phone 928 339 1935 www flo 2d com contact flo 2d com Purchasing Karen O Brien karen flo 2d com English 928 339 1935 Noemi Gonzalez Ramirez noemi flo 2d com Spanish 786 223 0410 Technical Support FLO 2D Karen O Brien karen flo 2d com 928 339 1935 Table of Contents Resources iii 3 Mantrals D rr 3 Workshop Lessons nun ann en 4 Power Point Presentations ecce detecte 4 Website www flo 2d com eene 5 bBEO2DIGense seseoeoeseoeseoendonesCoed UON UO UO 5 FLO 2D Suite of PfOSTAUDS icc ce aee oce eee 6 Set 7 General Ovet VIEW pt D 8 TEBAS CS osinon neeesser scope nere rere Pee nee ER snes 8 New Features and Enhancements ees 8 Porting From Version 2009 to the PRO Model 8 Get nbe StaftedissesegeocooeoosodC dodecened ede onion 11 What data is requited scie ooesocuces ocean 11 Before you Statt iiem rr MR ED ERR 12 Estimate the Project area s cedente tenerent 12 Selecting the grid element size eiae eei ss 13 Start simple tben add detail ssis iissa tem 14 Savina data aeq eru ur RR EORR REEL ER EXER REX UR tates 15 Building Project ee 2a een 16 Some General Guidelines ciere imer te ens 16 Mud and Debris Flow Simulation eee 1 Channel Hints and Gu
3. FLOWM DAT mudflow and then copy the appropriate file to INFLOW DAT before running the model 28 Guidelines Data Errors Data input errors may result in the model termination with an error message The error message will report a Unit number that is asso ciated with the data input file that contains an error Referring to these numbers may help you to debug input data errors Review ER ROR chk file for the report about potential errors encountered on Data files 9 OLER DAT 52 TREET DAT 10 CADPTS DAT 57 LEVEE DAT 30 CONT DAT 68 HYDROSTRUC DAT 31 FPLAIN DAT 85 XSEC DAT 32 RAIN DAT 89 RAINCELL DAT 33 INFIL DAT 95 EVAPOR DAT 34 INFLOW DAT 119 CHANBANK DAT 36 CHAN DAT 120 FPXSEC DAT 37 AREDAT 125 FPFROUDE DAT 38 MULT DAT 180 WSTIME DAT 39 SED DAT 1557 SWMMFLO DAT 50 OUTFLOW DAT A complete list of file unit numbers can be found in the Data Input Manual 29 Guidelines Troubleshooting Is the flood simulation running OK Volume Conservation and Numerical Surging There are several indicators to help address modeling prob lems The most important one is volume conservation The FLO 2D results should be reviewed for the following volume conser vation surging timestep decrements and roughness adjustments with limiting Froude numbers Any flood routing model that does not report on volume con servation should be suspected of generating or losing volume A
4. ARF s For large flood events the assignment of individual cell ARF values generally has limited effect on the area of inundation For local flooding detail individual grid element ARF assignment 35 Guidelines may be justified Channel Cross Section Adjustments Typically five to ten channel elements are represented by a surveyed channel cross section Selecting a cross section to represent the transition reach between wide and narrow channel segments re quires engineering judgment Use the PROFILES program to interpolate the transition between surveyed cross sections Channel Slope Adjustments Adverse channel slopes can be simulated by FLO 2D Smooth ing out an irregular slope condition over several channel ele ments to represent reach average slope conditions may speed up the simulation Cross sections with large scour holes can result in local adverse slopes that misrepresent the average reach con ditions Review the channel slope in PROFILES Street Flow Streets generally convey only a small portion of the flood volume but may be important for flood distribution to remote areas of the grid system Streets are important to flood delineation in urban areas High street velocities may cause numerical surging and slow the simulation down Assign reasonable limiting street Froude numbers to adjust the street n values Afew important things to consider Some modeling tips for unconfined flood simulations are present ed R
5. Tutorials Tutorials and lessons located in the FLO 2D help folder Doc uments FLO 2D Documentation flo_help will assist through out a project Please check the website to download any newly posted tutorials lessons Estimate the project area One of the keys to setting up an efficient model is to determine the project area and estimate a desired grid element size The project area 12 Getting Started should be located in a FLO 2D grid system so that it is not affected by either inflow or outflow conditions The inflow and outflow nodes should be considered as non essential nodes sources and sinks and these should be located outside the project influence area Selecting the grid element size Once the overall project area has been identified estimate the grid system size as a rough rectangle and determine the approximate number of grid elements that would be required for different size square grid elements such as 50 ft 100 ft 200 ft etc Selecting the grid element size will control how fast your FLO 2D flood simula tion will run FLO 2D users often choose a grid element that is smaller than necessary A small grid element combined with a high flood discharge can result in long flood simulations times To help with the grid element size selection the following criteria are suggested The estimated peak discharge e a divided by the surface area of the grid element A should be less than 10 cfs per square ft Opeak Asus l
6. nodes and add the variables in Line 2 in OUTFLOW DAT Channel Output Channel output can be reviewed in several ways The channel output data is written to a series of ASCII output files including BASE OUT HYCHAN OUT CHANMAX OUT DEPCH OUT and others The HYDROG program will display a plot of the hydro graph for each channel element It also has a routine to review average hydraulic conditions flow area bed shear stress hydraulic radius velocity etc in a channel reach covering sev eral channel elements that user can select in the HYDROG pro gram The PROFILES pro gram can be applied to review the water surface profile spatial variation in peak discharge mobile bed profiles water surface in each cross section or the cross section geometry changes associated with scour and deposition Finally MAXPLOT and MAPPER will graphically define the relationship between channel and floodplain volumes by map ping the inundated areas 25 Channel Hints Notes Notes 26 Modeling Guidelines Some Basic Data File Checks Grid System The grid system should begin with grid element 1 and have no missing element numbers There should be no dangling grid elements connected only by a diagonal If you add elements to the grid system after the model has been built the FPLAIN DAT and CADPTS DAT files will have to be edited A CHECKER exe program will verify the grid system accuracy Channel Flow The channel should b
7. review of the SUMMARY OUT file will identify any volume conservation problems This file will display the time when the volume conservation error began to appear during the simula tion Typically a volume conservation error greater 0 001 percent is an indication that the model could be improved The file CHVOLUME OUT will indicate if the volume conservation er ror occurred in the channel routing instead of the floodplain routing When troubleshooting components should be switched off and the model simulation run again until the volume con servation problem disappears This will identify which compo nent is causing the difficulty Some volume conservation prob lems may be eliminated by slowing the model down decreasing the timesteps using the stability criteria Most volume conser vation problems are an indication of data errors It is possible for volume to be conserved during a flood simula tion and still have numerical surging Numerical surging is the result of a mismatch between flow area slope and roughness It can cause an over steepening of the floodwave identified by spikes in the output hydrographs or water surface profiles Channel surging can be identified by discharge spikes in the 30 Guidelines CHANMAX OUT file or in the plotted hydrographs using the HYDROG program Maximum velocities also indicate surging To identify floodplain surging you can graphically review the maximum velocities plots in the MAXPLOT or Map
8. with the CONFLU 23 Channel Hints ENCE variables GDS present a list of each pair of sharing contiguous channel elements On your GDS project turn on Channel Confluences on View Components 5 If you have channel elements that will not share flow with the floodplain either overbank or return flow set the NO EXCHANGE parameter for the channel element For ex ample closed concrete culverts which should receive no floodplain inflow to the channel 6 To improve the timing of the floodwave progression through the system a depth variable roughness ROUGHADJ can be assigned on a reach basis The channel roughness should be assigned for the bankfull discharge condition Assigning ROUGHAD will result in an increase in n value with a de crease in flow depth during the flood simulation Channel Data Dependencies It is important to pay attention to variable dependency when simulat ing channel flow To simulate channel flow complete the CHAN DAT and XSEC DAT files and set ICHANNEL 1 in CONT DAT If you turn the ICHANNEL switch on in CONT DAT you must con sider revising other variables including CONT DAT Assign NOPRTC 0 1 or 2 for reporting additional channel output data INFLOW DAT Set IDEPLT grid element with a channel inflow hydrograph to plot a channel inflow hydrograph on the screen at runtime Assign IFC C for channel inflow hydrographs 24 Channel Hints OUTFLOW DAT Assign KOUT for channel outflow
9. D model and its processor programs prior to starting a new project Information about upcoming training sessions and webinars is posted to the webpage FLO 2D License The FLO 2D model license can be reviewed in the FLO 2D subdi rectory For the FLO 2D Basic Model the license allows unrestrict ed distribution and use The FLO 2D Pro Model is a site license and it states that the FLO 2D model can be loaded on any computer in the office of purchase The license does not include the right to copy or distribute the FLO 2D Licensed Software outside the license office The license does not permit the use of the FLO 2D model on a computer outside of the license office Resources FLO 2D Suite of Programs FLO 2D Two dimensional flood routing model for river and unconfined overland flooding GDS Pre processor program for graphically creating and editing FLO 2D grid systems and component data MAPPER Mapping software to display FLO 2D results PROFILES Pre processor and post processor program for graphic displays of the channel bed profile cross sections and predicted water surface profiles HYDROG Post processor program to display channel and cross section hydrographs Resources Set up Computational Requirements FLO 2D is compatible with the MS Windows operating sys tems including the newer versions of Windows Recommend ed minimum computer requirements are 4 gb RAM Faster is better Projects with a large grid sys
10. TRFNO streets When the computed Froude number exceeds the limiting Froude number the n value is slightly increased 0 001 for the next timestep This change in cell n value will improve the match between the slope flow area and n value dur ing the simulation When the limiting Froude number is no longer exceeded the n value is gradually decreased to the origi 32 Guidelines nal value The changes in the n values during the simulation are reported in the ROUGH OUT file For the next FLO 2D simu lation the n value adjustments can be made to grid element us ing the maximum n values reported in ROUGH OUT The maximum n values are also reported in FPLAIN RGH CHAN RGH and STREET RGH files that are created at the end of a simulation These RGH files can then be renamed as data input files DAT for the next flood simulation e g FPLAIN RGH FPLAIN DAT Reviewing and interpreting the results FLO 2D results include the maximum area of inundation maximum flow depth temporal and spatial hydraulic results channel or flood plain cross section hydrographs peak discharge and other hydraulic output Either the MAXPLOT or the MAPPER programs can used to graphically review the model output The flow depth results can be plotted as either line contours or shaded contours in MAP PER The FLO 2D flood simulation can be terminated at any time during the run by clicking on Exit on the window menu bar or by clicking the close bu
11. ainfall and Infiltration on Alluvial Fans Alluvial fan surfaces can be as large as the upstream watershed Fan rainfall can contribute a volume of water on the same or 36 Guidelines der of magnitude as the inflow flood hydrograph at the fan apex Infiltration losses can also significantly affect floodwave attenuation Infiltration losses should be calibrated with respect to the watershed percent loss by adjusting the hydraulic conduc tivity Spatial variability of the hydraulic conductivity can be as signed with the GDS program Sediment Bulking of Flood Hydrographs For a mudflow alluvial fan simulation sediment concentration can be adjusted in the INFLOW DAT file For desert alluvial fans sediment concentrations in flood events can reach 15 by volume For concentrations less than 20 by volume the flow will behave like a water flood The primary effect of increasing the sediment concentration is to bulk the flow volume Do not invoke the mudflow component MUD 1 in CONT DAT un less sediment concentrations greater than 20 by volume are expected Use the XCONC factor CONT DAT to bulk desert alluvial fan flows by 10 to 15 by volume Do not set both the MUD and ISED switches to on in the CONT DAT file in the same simulation Model Calibration and Replication of Flood Event Estimating flood hydrology both rainfall and flood hydro graphs can represent a significant departure from reality when replicating historical fl
12. animation and tem poral output one new output file is generated TIMDEP HDF5 in HDF5 binary format This file will replace the TIM DEP OUT file and improve data access speed and reduce file size Porting data files from Version 2007 and earlier FLO 2D Mod els Data files from model versions 2007 and earlier require that the data files first be updated to Version 2009 format to be able to format changes to Version PRO For data files versions prior to 2007 it is suggested that the data files be edited directly by re ferring to the Version 2009 Data Input Manual and using an ASCII text editor 10 Overview Getting Started What data is required DTM Data To start a FLO 2D model visualize the project area and compile available mapping imagery and digital terrain model DTM da ta The imagery and DTM points must have the same coordinate system If aerial imagery or digital topo maps are not provided with the project you may be able to purchase then through the in ternet The most common formats for digital imagery are tif sid and jpg files and these must have corresponding georefer enced world files e g tfw sdw and jew If photogram metric or LiDAR data are not available lower resolution DEM data can be used Elevation data formats that are accepted by the GDS are ASCII x y z data sets and elevation shape files Hydrologic data Hydrologic data for FLO 2D flood simulations include both rainfall and dis
13. cantly more timestep decreases than the other elements listed in the file the attributes of the sticky grid elements such as topogra phy slope or roughness can be adjusted The goal is to make the 31 Guidelines model run as fast as possible while still avoiding numerical surg ing If a floodplain element is causing most of the timestep decreas es check the SURFAREA OUT file to determine how much sur face area is left in the floodplain element for flood storage If the floodplain element contains a channel bank there may be very little surface area left for flood storage This will cause the model run slowly with exchanges the flow between the channel and flood plain To fix this problem 1 Remove other components from the channel bank element including streets or ARF values 2 Shorten the channel length XLEN in CHAN DAT This will increase the surface area in the channel bank floodplain elements 3 Decrease the channel cross section width in the PRO FILES program Limiting Froude Numbers There is a unique relationship between floodwave movement and wave celerity and the average flow velocity defined by the Froude number This physical relationship between the kinematic and gravitation forces involves the slope flow area and flow re sistance To use the limiting Froude number estimate a reasona ble maximum Froude number for your flood simulation and as sign values to FROUDL floodplain FROUDC channels or S
14. charge hydrographs These data bases can usual ly be obtained from the local state or federal agencies It is suggested that the hydrologic data be carefully reviewed because the flood volume will determine the area of inundation The us er must also decide whether infiltration and evaporation losses will be simulated Floodplain and channel detail If river cross sections bridges culverts buildings and streets ate to be simulated the user must be able to locate these fea tures with respect to individual grid elements Aerial imagery is 11 Getting Started invaluable for this purpose Component data may be required for these components Bridges and culverts will need rating curves or tables Streets will need width and curb height data River cross sections may have to be surveyed or extracted from DTM data bases Before you start Check for updates and work through the tutorials and workshop lessons that pertain to your project In addition review the FLO 2D License Agreement on page iii of the FLO 2D User s Manual to understand your options for installing the program on multiple com puters Updates When starting a new FLO 2D project the first step is to visit the website www flo 2d com and download any model proces sot program manual or document updates New features are added to the programs throughout the year Program revisions and bug fixes are listed on the web site in the FLO 2D Model Revisions document by date
15. e grid elements should be individually assessed in terms of elevation n value slope and surface area To speed up a slow simulation in addition to modifying the cell or channel attributes you can increase the Courant numbers The default values for the Courant numbers for floodplain channel and streets is 0 6 If the DEPTOL or WAVEMAX stability parameters are being applied the TIME OUT file will list the grid element timestep decreases associated with these parameters Adjustments can be made to these parameters to speed up the model Primarily the focus should be on improving the rela tionship between the flow area slope and roughness for the specific grid or channel elements The guidelines for applying the numerical stability parameters are as follows 38 Guidelines Initially run the model with Courant numbers 0 60 DEPTOL 0 and WAVEMAX 0 and an appropriate limit ing Froude number e g FROUDL 0 9 subcritical flow on an alluvial surface The timesteps are varied only by the Courant stability criteria Review the maximum velocities in MAXPLOT or MAP PER to determine the location of any inappropriate high velocities related to numerical surging and increase the n values of all the grid elements in the vicinity You can also review VELTIMEC OUT channel and VELTIMEFP OUT floodplain Increase the cell n values for those elements and the contiguous neighbors with un reasonable high velocities You can automate the n
16. e an octagon shape NW 1 NE 8 5 w E a 2 sw S SE 7 3 6 Saving data When you are running many project simulations save the data files fre quently Suggestion Use one folder for project testing and a differ ent one for project editing 15 Getting Started Building a Project Create a Project Folder Start by creating a subdirectory for the project data files and im port the DTM data base files maps and aerial photos Build the Project Files Use the GDS to build a grid system Data files can be graphically created in the GDS You can follow the GDS Getting Started lesson to initiate a project For easy access put the GDS icon on the desktop Run the FLO 2D model Once the eight required basic data files have been created CADPTS DAT FPLAIN DAT TOPO DAT MAN NINGS_N DAT CONT DAT TOLER DAT INFLOW DAT and OUTFLOW DAT an over land flood can be simulated You can run a FLO 2D simulation by 1 GDS click on Run FLO 2D command in the File menu 2 Double click on FLO EXE in the project subdirectory Put FLOPRO EXE in the project folder first Some General Guidelines Data Input When the data format seems confusing review the example pro ject data files provided in the Example Projects subdirectory of the FLO 2D Documentation folder File Management The output files in the project folder will be overwritten during 16 Build a Project subsequent model runs To save any output f
17. e organized from upstream to down stream in CHAN DAT and should be continuous At a channel confluence the downstream main channel grid ele ment must be lower in elevation than the confluence element Eliminate channel elements with a channel length XLEN less than 50 of the grid element side width Instead connect the channel elements across the diagonal Create a positive bed slope at channel inflow and outflow nodes 27 Guidelines Inflow Outflow Nodes Inflow and outflow nodes should not have other components such as hydraulic structures streets ARF s etc Outflow nodes should not be doubled up Outflow nodes should have up stream floodplain elements as neighbors Use only one line of outflow nodes Minimize the outflow nodes Separate the out flow nodes from other components such as levees or hydraulic structures by 3 5 elements Inflow elements are sacrificial and their purpose is to get the flow on the system without slowing down the model You can split the inflow uniformly between several floodplain elements to speed up the model when a very high peak inflow discharge is assigned For the channel you can create an artificially large cross section to accomplish the same results Create separate input hydrograph file for clear water or mud flow simulations The sediment concentration assigned to the discretized hydrograph has to be removed for a water flood simu lation Create one file INFLOWW DAT for water and IN
18. ection shape for each channel element will be interpolated between those channel elements with assigned cross sections Assign the Channel length Within the Grid Element The channel length XLEN within a grid element is calculated by the GDS automatically The channel lengths are then summed and reported by GDS for each segment The river cen ter line distance can be estimated with the GDS Measure Dis tance along a Line tool The individual XLEN values can then be adjusted so that the reach length is exact Adjust the Channel Bed Slope and Interpolate the Cross Sections The cross section geometry and slope can be re interpolated between any two channel elements in the PRO FILES program The result of this interpolation is an adjusted cross section shape and bed slope The assigned surveyed cross sections retain their original shape and elevations The bed slope for rectangular and trapezoidal can also be adjusted Assign the Manning s n value Initially a uniform Manning s n value can be assigned to all the channel elements Using the limiting Froude number FROUDC in Line 1 of the CHAN DAT file spatially variable n values can be adjusted The n value should represent a com 22 Channel Hints posite flow resistance for the entire channel including bed irreg ularities obstructions vegetation variation in channel geometry channel expansion and contraction potential rapidly varying flow and variable river platform Poor s
19. election of n values particularly underestimating n values or failure to pro vide spatial variation in roughness can result in numerical surging Additional Channel Data Instructions The user can select several options when setting up the channel data file including grouping the channel elements into segments specify ing initial flow depths identifying contiguous channel elements that share discharge CONFLUENCE identifying channel elements that don t share discharge with the floodplain NOEXCHANGE assign ing limiting Froude numbers and specifying depth variable n value adjustments These options are discussed in more detail in the CHAN DAT file description in the Data Input Manual A few in structional comments follow T Organize the channel segments and elements from upstream to downstream with the channel inflow element being the first element in the file Dividing the channel into segments by cross section geome try may facilitate organizing and reviewing the results For example a segment may represent a tributary or a concrete section of the main channel The key to accurate channel routing is to balance the rela tionship between the slope flow area and roughness Chan nel routing is usually more stable if the natural cross section routing routine is used Use at least 10 stations to define a cross section Channel elements that are contiguous and share discharge e g tributaries must be identified
20. idelines eene 20 Overviewasussesikuenuunnenbnekenekemeborebtihe 20 Creating the Channel Data File erre 20 Additional Channel Data Instructions sse 23 Channel Data Dependencies etate 24 Modeling Guidelines ea 21 Some Basic Data File GBecks aeaceosceoeocoeseoen eoo 24 D ta EXtOtS p 29 Reviewing and interpreting the results ssssss 33 Make some adjustments sos ee eoe ore doe 34 A few important things to consider 36 Improving model speed and stability cesses 38 How t speed up the FLO 2D model 38 Makino Flood Maps iiec accen aenea eee 42 Resources Manuals FLO 2D manuals deliver electronically are provided in the FLO 2D Documents folder The manuals are FLO 2D Reference Manual The Reference Manual provides an overview of 2 dimensional flood routing Modeling theory and the FLO 2D component system is discussed There are some instructional comments and discussion of modeling parameter data including sediment transport roughness and infiltration Data Input Manual The data input manual contains descriptions of all the input pa rameters There are instructions for installation and getting started as well as for using the pre processor and post processor programs The manual also discusses data range and limitations output files and a trouble shooting GDS Manual This manual contains a description of the GDS componen
21. iles that might be overwritten rename the file or create a new folder copy all the DAT files into it and then run the new flood simulation in that folder Graphics Mode To view a graphical flood progression over your project flow domain follow these steps 1 Click File Run FLO 2D on the GDS and turn on the graphics display switch LGPLOT 2 in CONT DAT file selecting Detailed Graphics in the Time Control and Plot Variables dialog Assign an update screen refresh time Update Time Interval on Graphics Display in the lower right hand corner of the FLO 2D Control Variables to 0 05 or 0 10 Simulating Channel Flow To add a main channel to an overland flood routing routine fol low this procedure 1 2 Review workshop lesson 3 4 and 5 If surveyed cross section data is available create the XSEC DAT file first Then generate the CHAN DAT file in the GDS Interpolate the cross section data in the GDS or in PRO FILES Set the Main Channel check box switch ICHANNEL 1 in the CONT DAT file Prepare any channel inflow hydrographs in the file named INFLOW DAT Select a channel inflow hydrograph to be plotted IDEPLT in INFLOW DAT file 17 Build a Project Ts 8 Assign channel outflow node s in OUTFLOW DAT Review the Channel Hints and Guidelines section Mud and Debris Flow Simulation Simulating mud and debris flows requires additional data 1 Turn On the MUD switch o
22. it the data the grid developer system GDS program is used Other FLO 2D pre and post processor program can be called from the GDS New Features and Enhancements New model components and features are frequently added to the FLO 2D model system resulting in a new release about once every two years Between new releases updates minor enhancements and bug fixes are posted to the website as necessary typically on a monthly basis New features may include new components such as storm drain model interface more efficient computational code enhanced multi processing code or new sediment transport equations See the web site for the new features in the next version Porting From Version 2009 to the PRO Model A converter program CONVERTER_PRO exe was created to au tomate the required data file revisions to port the Version 2009 data files to the Pro Model format It may be necessary to update older 8 Overview model data files to version 2009 before porting to the Pro Model The main data file revisions can be summarized as follows initiation switch for surface water storm drain exchange in CONT DAT indi vidual Courant number assignment for floodplain channel and streets in TOLER DAT timestep accelerator in TOLER DAT ex tension of the Width Reduction Factors for eight flow directions in ARF DAT elimination of the NOFLOC s and creation of the new confluences in CHAN DAT parameter to enable runoff from the ARF area of the g
23. ith debris 0 10 0 20 34 Guidelines Shallow Flow on asphalt or concrete 0 10 0 15 Fallow fields 08 0 12 Open ground no debris 04 0 10 Asphalt or concrete 02 0 05 Spatial variation of n values can affect the floodwave progres sion travel time and reduce surging but may not significantly impact the area of inundation particularly for longer flood du rations When assigning n values the focus should be on the total flow resistance not just the roughness associated with bed friction Consider flow expansion and contraction flow in bends form drag and other potential non uniform flow conditions When adjusting n values review the TIME OUT and ROUGH OUT files to complete the n value revisions Edit Topography The interpolation of DTM points to assign elevations to grid el ements is not perfect even when the GDS filters are applied It may be necessary to adjust some elevations on the floodplain af ter you review the result MAXPLOT and Mapper can be used to quickly locate grid elements with unreasonable flow depths that may constitute inappropriate depressions Flood plain depressions can sometimes occur along a river channel if too many D TM points located within the channel banks Floodplain Surface Area Reduction The distribution of flood storage on the grid system can be affected by buildings and obstructions This loss of storage can be represented by assigning area reduction factors
24. lood maps e Contour line width and shaded contour may splash over floodplain features such as levees and this can affect map resolution appearance e Computing and plotting flow depths over the DTM points improves the inundation map resolution e Map resolution controls include contour intervals All CADD and GIS programs have to accommodate topographic data base resolution and contour splash e g flood contours that cover levees buildings bluffs or other features Map resolution is a function of the point density grid element spacing contour line width and plotting algorithm Mapper has options to address these resolution issues Maximum flood depth computation over DTM points By importing the DTM ground elevation points into Mapper and subtracting the ground elevation from the FLO 2D predicted maxi mum grid element water surface elevation flow depths are computed for every DTM point Plotting the DTM point flow depth shaded contours instead grid element shaded contours will greatly enhance the map resolution A file FLO2DGIS OUT of these D TM point flow depths can also be created to import this data to GIS Shapes file generation Mapper automatically generates shape files for each flood map in the project folder that can be imported to GIS or CADD programs for further editing 43 Flood Maps
25. oods When attempting to match measured flood stages high water marks or channel discharges focus first on obtaining a reasonable estimate of the flood volume then concentrate on the model details such as n values ARF s and street flow Remember that flood volume is more important than peak discharge for a flood routing simulation 37 Guidelines Improving model speed and stability The FLO 2D PRO model increases the role of the Courant number to control the magnitude of the computational timestep By varying the Courant number within a limited range of the assigned value the number of ineffective timestep reductions can be decreased This enables the computational timestep to gradually adjust to numerical stability criteria The PRO model has eliminated the dependence on DEPTOL and WAVEMAX stability parameters The dynamic wave stability criterion WAVEMAX is now a secondary option to control the timestep For most overland flow applications including those involving overbank rivers flooding the Courant number will suffi cient for numerical stability The dynamic wave stability criterion remains an option for more complex river simulation How to speed up the FLO 2D model Slow model flood simulations typically have timesteps that are less than 1 second and a large number of grid elements in excess of 1 million cells Review TIME OUT to determine which grid elements are the culprits in slowing down the model The attributes of thes
26. per post processor program You can also review the VELTIMC OUT channel or VELTIMFP OUT floodplain files for unreasonable maximum velocities Surging can be re duced or eliminated by increasing n values or decreasing stability criteria TOLER DAT Reducing the Courant number will de crease the timesteps If the decreasing the timesteps fails to eliminate the surging then individual grid element topography slope or roughness should be adjusted This can be accom plished in the GDS for floodplain flow For channel flow the PROFILES program can be used to make adjustments to the cross section slope or geometry For channel surging abrupt transitions in flow areas between contiguous channel elements should be avoided Setting a lower limiting Froude number for a channel reach may also help to identify the problem Sticky Grid Elements When the flood simulation is running slowly the TIME OUT file can be reviewed to determine which grid elements are causing the most timestep decreases TIME OUT lists the top twenty floodplain channel or street elements sticky elements that caused the model to slow down The file also sorts the timestep decreases by the stability criteria Adjustments can be made in the stability criteria to more equably distribute the timestep de creases The model is designed to advance and decrement timesteps so there have to be grid elements listed in the TIME OUT file If one or two grid elements have signifi
27. ption check box in CONT DAT file Turn off the XCONC and ISED sediment transport switches in the CONT DAT file form Create the M line Line 1 in the SED DAT file Assign sediment concentrations or volumes to the inflow hydrographs in the INFLOW DAT file Review the document Simulating Mudflow Guidelines in the FLO 2D flo help folder Modeling Sediment Transport Mobile bed simulation is complicated and should be attempted only after a rigid bed model is fully functional 1 Turn on sediment transport switch ISED 1 in the CONT DAT file form Turn off the mudflow switch MUD 0 and set XCONC 0 00 in the CONT DAT file form Assign the SED DAT file sediment parameters For channel sediment transport set ISEDN 1 for each channel segment in CHAN DAT Read the Sediment Transport Total Load section in the FLO 2D User s Manual 18 Build a Project discharge cfs im s cms length depth ft m hydraulic conductivity inches hr mm hr Rainfall abstraction inches mm soil suction inches mm velocity fps mps volume acre ft m cm viscosity poise dynes s cm poise yield stress dynes cm dynes cm 19 Build a Project Channel Hints and Guidelines Overview Review the CHAN DAT file description in the Data Input Manual It includes a list and explanation of all channel variables and instruc tions on how to apply them The mos
28. rid in RAIN DAT and extension of infiltration capabilities in INFIL DAT Other enhancements involve optional data or components CONT DAT Surface water storm drain exchange can be simulated with a runtime interface with the EPA SWMM model The new switch to initiate the storm drain component is SWMM at the end of line 3 seventh variable A default of no storm water simulation is SWMM 0 CHAN DAT Confluence pairs replace the NOFLOCs in the CHAN DAT file This data input revision is automated with the CONVERT ER PRO program RAIN DAT The switch IRAINBUILDING enables the rainfall on buildings to contribute the runoff on the grid element instead of being an assumed storm drainage loss INFIL DAT Spatially variable depth limited infiltration storage parameter and a global hydraulic conductivity adjustment factor were add ed to the INFIL DAT file Overview Optional Data File Revisions For better integration with GIS and CADD programs two new data files are generated automatically by the GDS and FLO PRO Model TOPO DAT and MANNINGS_N DAT New op tional data files include FPFROUDE DAT spatially variable limiting Froude number SWMMFLO DAT storm drain inlet geometry and OUTRC DAT depression storage rating tables There are also optional revisions in the following files HYS TRUC DAT SED DAT CONT DAT LEVEE DAT and BREACH DAT Binary backup files allow simulations to be re started from the last output interval For
29. s must be neighbors Assign the Preliminary Channel Data The GDS will list the selected channel elements in a dialog box Preliminary channel data such as shape channel element number channel extension direction roughness n value channel length and cross section number can be assigned in the channel editor dialog box Define the Right Bank Element The channel width can be larger than the grid element For ex ample a channel may be 1000 ft wide while the grid element is only 200 ft wide The left and right bank elements can be sepa rated by several grid elements The channel component interacts with the right and left bank elements to share discharge with the floodplain Each bank element can have a unique top of bank elevation Assign the Cross Section Number Assign the surveyed cross section number in XSEC DAT to the corresponding channel element in CHAN DAT Assign a zero 21 Channel Hints 0 value to the rest of the channel element cross section num bers Typically there are only a limited number of cross sec tions and many channel elements Before interpolation there fore the channel profile will look like a staircase After you click on the GDS Interpolation button each channel element will have a unique cross section and bed elevation and the cross sections numbers in XSEC DAT and CHAN DAT will corre spond and will be renumbered from top to bottom starting with cross section number 1 Both the slope and cross s
30. t 10 cfs ft 3 cms m If the Qpear Asurf is greater than 10 cfs ft the model should be expected to run more slowly After the grid element size has been selected proceed with establish ing the grid system using the GDS There are GDS workshop lessons to assist you in getting started on a new project Estimated FLO 2D simulation times are listed below for a short flood duration of 24 hrs ot less 13 Getting Started lt 50 000 Fast minutes 50 000 100 000 Moderate hour 100 000 1 000 000 Slow hours gt 1 000 000 Hours to Day or more Start simple then add detail The first flood simulation for any project will be a simple overland flow model upon which a more detailed flood simulation will be gradually built A suggested order of component construction is as follows Rain fall Infiltration Channels Levees Streets Buildings Hydraulic Structures culverts weirs and bridges Multiple Channels rills and gullies Mud and debris flows sediment transport As new components are added to a model and tested other compo nents switches can be turned off in the CONT DAT file FLO 2D routes flows in eight directions as shown in the following figure The four compass directions are numbered 1 to 4 and the 14 Getting Started four diagonal directions are numbered 5 to 8 Some components such as levees ate placed on boundaries of the grid element The grid element boundaries creat
31. t important aspect of simulating channel flow is to correctly balance the slope flow area and roughness to replicate field condi tions In the FLO 2D model river flooding using the channel com ponent is simulated as one dimensional depth averaged flow Each channel element is represented by rectangular trapezoidal or sur veyed cross section Simulating river flow requires the following data e Channel location with respect to the grid system e Channel roughness e Length of channel within the grid element e Channel cross section data Channel slope is computed as the mean bed elevation difference be tween the channel elements Channel elements must be contiguous to be able to share channel discharge Creating the Channel Data File The procedure for creating a river channel simulation is as follows see Channel and PROFILE Lessons 20 Channel Hints Select Channel Cross Sections River cross section survey data is organized in the XSEC DAT file with a station and bed elevation format Each cross section may represent one or more channel elements Each channel el ement is assigned a cross section in the CHAN DAT For chan nel design projects a rectangular or trapezoidal cross section may be selected Locate the Channel Element with Respect to the Grid System Use the GDS processor programs to identify the left bank channel element see the GDS Channel Lesson 4 For flow to occur through a river reach the channel element
32. tem gt 1 000 000 cells can put a demand on older computer systems Installation To install the FLO 2D software package onto the computer hard drive download the installation files to your computer and initi ate the SETUP exe file The default installation subdirectory for the model is C Program Files x86 FLO 2D Resource materials are loaded into a subdirectory identified as FLO 2D Documentation in the standard location named Documents by Windows The final step of installation is software activation For activation key email us at activation flo 2d com Un install You can remove the FLO 2D program and all of its attendant software from your computer using the standard Windows Re move Program procedure From the control panel run the Re move Programs utility and remove FLO 2D Some of the ex ample projects and document may still be in FLO 2D folder To complete the un install process delete the FLO 2D subdirecto fy Set up General Overview The Basics FLO 2D was written in the FORTRAN 95 computer language There are other coding languages embedded in the model Depending on your computer speed project application and flood duration the flood simulation might have a runtime ranging from 5 minutes to more than a day The code has been optimized for 64 bit multiple processor computers Virtually any Windows computer will suffice but faster and bigger is better To generate the basic data files and graphically ed
33. ts and all the graphic data editing and viewing tool commands It has a section on Getting Started and detailed images to help the user apply the FLO 2d model Mapper Manual This manual contains a description of the MAPPER com ponents and tools It has detailed instruction on creating flood 3 Resources maps Workshop Lessons The FLO 2D Software package comes with workshop lessons and tutorials to help the user utilize the many components and features These include Workshop Lessons Lesson 1 Getting Started GDS Lesson 2 GDS Component Editing Lesson 3 GDS Channel from scratch Lesson 4 HEC RAS Cross Section Conversion Lesson 5 PROFILES Cross Section Interpolation Lesson 6 Creating Flood Maps with MAPPER Lesson 7 Rainfall and Infiltration Lesson 8 HEC RAS to FLO 2D Conversion Lesson 9 Hydraulic Structures Lesson 10 Levees Walls and Berms Lesson 11 Streets and Buildings Lesson 12 Dam Breach Power Point Presentations Many of the Power Point presentations that are used in FLO 2D short courses and training are available at the FLO 2D website These Power Point presentations cover most of the FLO 2D features and components Resources Website www flo 2d com The FLO 2D website contains extensive information about flood modeling You can also download models updates and purchase services Updates to the FLO 2D programs are posted at the website frequently Check for new updates to the FLO 2
34. tton in the upper right hand corner of the window The simulation will terminate after the current timestep is completed and the output files will be generated and saved This enables the user to recognize if the flood simulation is running poorly e g too slow or not conserving volume and stop the simulation without losing the opportunity to review the output data It is also possible to restart the flood simulation from the point that the model was terminated by using the binary file backup option IBACKUP 1 33 Guidelines Make some adjustments The following adjustments to the data files may improve the simula tion and speed up the model Spatial Variation of n values Most numerical surging is due to underestimated n values The n values listed below represent steady uniform flow a condition rarely encountered during flooding Dense turf 17 0 80 Bermuda and dense grass dense vegetation 0 17 0 48 Shrubs and forest litter pasture 0 30 0 40 Average grass cover 0 20 0 40 Poor grass cover on rough surface 0 20 0 30 Short prairie grass 0 10 0 20 Sparse vegetation 0 05 0 13 Sparse rangeland with debris 0 cover 0 09 0 34 Plowed or tilled fields Fallow no residue Conventional tillage Chisel plow 0 008 0 012 Fall disking 0 06 0 22 No till no residue 0 06 0 16 No till 20 40 residue cover 0 30 0 50 No till 60 100 residue cover 0 04 0 10 Open ground w
35. value adjustments with the limiting Froude number assignments for floodplain channel and street flow Review the n value revisions in ROUGH OUT Make n value adjustments in the files FPLAIN RGH and CHAN RGH for any high n values in ROUGH OUT Also make roughness adjustments for any observed high maxi mum velocities then replace FPLAIN DAT with FPLAIN RGH or CHAN DAT with CHAN RGH The same approach can be used for the streets Run the simulation and continue to replace FPLAIN DAT and CHAN DAT until ROUGH OUT is essentially empty A few incremental n values changes in ROUGH OUT will not affect the simulation or the area of inundation If the model simulation still has numerical surging evi denced by hydrograph spikes or high velocities after the limiting Froude number n value adjustments reduce the Courant numbers by 0 1 e g from 0 6 to 0 5 The Courant number range is 0 2 to 1 0 If inappropriate high velocities are persistent run the model 39 Guidelines with Courant number reductions first then assign the DEPTOL 0 2 and WAVEMAX 0 25 and review the TIME OUT file Also note the change in timesteps report ed in SUMMARY OUT It may be necessary to make DEPTOL and WAVEMAX adjustments if the model is too slow The result of following this procedure will be e A calibrated model for overland roughness values in which the discretized numerical system in both time and space will better simulate the movement of the floodwave
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