Chris Smemoe

WMS Development Team
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Everything posted by Chris Smemoe

  1. Hi, There is a way to re-extract and update only selected cross sections but it's not an easy procedure and would require you to edit some of the WMS .map and cross section database files using a text editor. I guess I don't really recommend this approach. I guess you have a couple of options. One is the approach you mention, where you extend any cross sections that don't intersect the bank lines so they're beyond the bank lines. This would require you to re-extract all your cross sections, and your edits based on survey data would be deleted. You would need to re-enter your survey data for each of your cross sections in this case. This should not be too difficult since you should already have the survey data saved as a cross section database file. It would just be time-consuming, especially if you have lots of cross sections. Another approach is to edit each cross section's geometry and point properties by going to the cross section attributes | Assign Cross Section | Edit and then adding the left and right bank stations manually into the Point Props window. The drawback of this method is that your left and right overbank lengths will not be computed by WMS for the cross sections where the left and right banks are manually defined. When you run HEC-RAS, you will get an error message for each of these cross sections. You can then compute the left and right overbank lengths for these cross sections using the measure tool in WMS. You would have to re-enter these lengths in HEC-RAS each time you export your model from WMS. So it may be worth it to you to update your cross section arcs in WMS, re-extract the cross sections, and re-merge your surveyed cross sections, but that's up to you. I agree that it would be nice to just update selected cross sections in your cross section database file, but this option is not yet available in WMS. Hope this helps, Chris
  2. Thanks for the input. I have noticed this also. I added a request to create a fill box for the color legend. This should be fixed in a future download of WMS.
  3. Anything is possible, but this would be difficult or impossible to do just using the HMS interface. You'd probably have to edit the HMS text files using a text editor or use WMS to combine models somehow. Chris
  4. I had another few thoughts on this issue you're having with the cross sections. I will insert some of your original questions: I don't have any general rules of thumb, though I think you can generally assume that your surveyed cross sections are more correct than your extracted cross sections. Since your surveyed cross sections are more correct than your extracted cross sections, I think you can assume that you can line up your cross sections using the east bank, as in screen shot B. This is assuming that your surveyed cross sections extend to the east bank as extracted from the DEM. It could be that your surveyed cross section extends only to a certain point (not to the bank point) on the extracted cross section. In this case, you would line up the east bank of your survey cross section at that same point on your extracted cross section. If you have good elevation values on your surveyed cross section, you could approximate the location of this point along your extracted cross section. Yes, I think the odd shape will impact your RAS model. You want your cross sections to be as similar as possible from one cross section to the next downstream cross section in your model. This is especially true for running an unsteady RAS model, where abrupt changes in cross section geometry can cause model instabilities. You could try filtering/removing points along your extracted cross section using the filter tool in the cross section attributes dialog or just by removing them manually before merging cross sections. It looks like you have lots of points in your channel cross section. This can be a good thing, but can be problematic if you're trying to merge cross sections where the geometry does not match. I hope this helps, Chris
  5. I don't have any general rules of thumb regarding which bank to use to align your cross section in your model. I can tell you how to fix the problem you're having with the strange shape when you insert the survey cross section based on the lower bank. One way to fix this is to add an additional point to your survey cross section so your cross section is long enough to be inserted into your extracted cross section without any gaps. I don't know if this makes sense. You should probably always use the "Insert All" option when merging instead of the "Blend All" option when merging. Hope this helps, I'll think more about which bank station to use and if anything comes to me I'll reply to this thread. Chris
  6. There are various ways of computing the lag time for a diversion. It's up to you to determine the method you want to use to compute the lag time and any losses for the diversion. Normally you wouldn't have the same lag time for all the diversions in your watershed unless all the diversions have the same length, slope, and geometry. It would be best to either calculate the lag time manually or to use the Muskingum-Cunge method where you define a diversion length, slope, and the channel geometry. HMS will compute the lag time if you use this method. There are not really any good tools for calculating the lag time for a diversion in WMS for an HMS model. The diversions would have to have the same geometry, length, roughness, and slope for the lag time to be the same. The impact the lag time has on the model calculations is that the hydrograph downstream of the diversion is routed based on the lag time. This means if the lag time for a diversion reach is 30 minutes, it takes 30 additional minutes for the hydrograph to reach the downstream end of the diversion and the hydrograph peak is translated by 30 minutes. There's also a storage attenuation of the hydrograph that occurs along the diversion reach that will decrease the peak flow when the hydrograph is routed using some of the HMS routing methods. Chris
  7. I'm not sure why it's saying the Snyder method. My version of HMS actually did not show the same screen as yours. I wonder what version of HMS you're using. I'm using version 4.1. Send an email to or call Aquaveo Tech support if you want somebody here to look at your model and possibly help you. As far as the style sheets and the reports menu, it's complicated to use. A simple search on google for "Reports menu HMS style sheets" turns up some good results. The best ones I've found are from HEC here and another one here. You could just modify the style sheets included on these sites as needed. Figuring out what names to use in the style sheets and the format is the hard part. I don't have a good source for that. Hope this helps, let me know if you're able to figure out anything with the kinematic wave routing. You could always use the Snyder or Clark transform or just the SCS transform if nothing else works and if that option is available to you. Chris
  8. Ayman98, I do not recommend using the "lake" polygon attribute in the drainage coverage. If you need to define a lake, just define a basin as you normally would (the basin would include the lake, but the lake would not be represented by a polygon or arcs in your watershed) and then convert the basin's outlet point to a "reservoir" type by going to the hydrologic modeling module, right-clicking on the outlet, and then select Add | Reservoir. Then define your HMS reservoir data in the HMS Properties dialog. There are several ways of defining a reservoir in HMS. In general, you need some sort of storage-capacity-discharge curve that is a plot of the volume of water in the reservoir and the outflow from the reservoir at different elevations. There are tools in WMS to help you generate these curves. To get to the tools, Select the reservoir outlet and then select Calculators | Detention Basins to define your storage capacity-discharge curves and then map the curves to the HMS model when you're done. Hope this helps, Chris
  9. Ayman98, You can specify a sink in HMS. Any water that enters a sink just leaves the watershed and does not contribute to the watershed hydrograph. I don't know if this is what you want, but this may be an option for you if you have something like this. You could also model something like this using a diversion if you want some water to bypass the injection well and continue to the watershed outlet point. In either case, you could not model what's happening with the groundwater using HMS. You'd have to use some other model like GSSHA if you want to model surface-groundwater interaction. Or you could run HMS and take the hydrograph from the diversion or sink and use this as an injection well input to a groundwater model like MODFLOW. WMS has options to add sinks or diversions at outlet points. Just right-click on the outlet and select Add | Diversion or Add | Sink. When you export the HMS model, the diversion or sink will be included with your model. There's also a loss model in HMS called the SMA model that you might find useful for what you're doing. The SMA model divides the losses into several layers or "buckets", such as the canopy, soil, and a couple of percolation layers. Any water that exits the second percolation layer is assumed to go to the groundwater. You could use the output from the second percolation layer to determine how much water is entering the groundwater aquifer from your watershed. I don't know how you would use this method with an injection well like yours though. Hope this helps, Chris
  10. I am certainly not an expert on the Kinematic wave method implemented in HMS. I wonder if you increase the number of subreaches on your kinematic wave channels and/or on the overland flow plane. The default is five, but maybe increasing this value will make it so you don't get the first warning you're getting related to the time step. Increasing your channel length by an order of magnitude and decreasing your slope by an order of magnitude should change your results, but maybe not by as much as you think. I tried changing these numbers on a basin and increasing channel length/decreasing slope by a factor of 3 or 4 for each value resulted in only a 2% change in the peak flow. The resulting hydrograph was slightly attenuated when I decreased the slope, and this was expected. The amount of change in your peak flow (if nothing else has changed) seems low if you're referring to the results from changing a single basin in your model. I have no idea why your method would show the Snyder method when you print the results. How are you printing the results? Are you using the HMS reporting tools in the Tools | Reports menu? I usually look at the results in the "Results" tab in the HMS interface and I don't see a place where it prints the transform method in this area. HEC does not provide direct support for their models, but you could try reporting your problem as a bug report to HEC and see if they respond to your problem or help with your modeling issues. Their bug report page is located here: Hope this helps. Let us know what you figure out so others will know how to solve similar problems, Chris
  11. We are pleased to announce that a GSSHA course will be held free of charge to a limited number of attendees. Government workers with expertise in hydrology have highest priority in attending this course. Please contact Chris Smemoe at Aquaveo or see the information below for more information about this course. Workshop on Watershed Modeling with GSSHA April 11-13, 2017 Arctic Hydrology in GSSHA April 14, 2917 Hydrologic Engineering Center, Davis, California You will learn the basics of: • Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model, developed at the U.S. Army Corps of Engineers, Engineering Research and Development Center and the University of Wyoming • Dept. of Defense Watershed Modeling System (WMS), developed by Aquaveo LLC • Spatial data needed to estimate distributed GSSHA model parameters, including data requirements, basics of GSSHA/WMS and how to find and use spatial geographic data to develop GSSHA models using the WMS Hydrologic Model Wizard. • Simulating Arctic hydrology with GSSHA in the one day course feature on April 14. The GSSHA model with WMS support constitutes a complete watershed analysis system that can be used for a variety of hydrologic science and engineering computation and design evaluation, such as flood simulation, hydrologic impacts of land use change, and best management practice design and testing of flood mitigation measures. This course will feature new developments in sediment transport and artic hydrology. Course Layout: Through a combination of lectures and experiential applications, the course features the spatially distributed modeling components of this system. The course begins with an overview of the capabilities of the WMS to ensure maximum benefit from the hands-on portions of the class. Attendees will learn to use WMS to set up GSSHA models that include overland flow, infiltration, distributed rainfall, hydraulic structures, continuous simulations, flood inundation mapping, and sediment transport. A one day course on Artic Hydrology will feature snow melt accumulation and melt, simple methods in GSSHA to simulate seasonally frozen soil, and soil water/thermodynamic modeling in GSSHA for seasonally frozen soils as well as permafrost regions. Outcome: Having completed this course, attendees will gain a working knowledge of the U.S. Army Corps of Engineers (USACE), Engineer Research and Development Center (ERDC) GSSHA model that is supported by the Watershed Modeling System (WMS) interface software. You will also understand how, when, and why you might be able to apply the tools to specific studies as well as understand the input data requirements. This class provides the user with sufficient background to easily set up a sophisticated hydrological model. Who Should Attend? The course is intended for anyone interested in flooding, the effects of landscape changes on hydrology, and/or analyzing best management practices and flood control measures, sediment transport and cold regions hydrology. Experience with hydrologic modeling and numerical methods are a plus but not absolutely required. Some college-level background in hydrologic science and/or engineering is required. Instructors: This short course will be taught by the lead GSSHA developer Dr. Charles W. Downer and GSSHA developer and cold regions expert Dr. Nawa Raj Pradhan, USACE-ERDC. Utility: Once GSSHA models are developed, they can be archived and run in the LINUX supercomputer environment. The GSSHA code is parallelized using OpenMP for execution on multi-core CPUs and is being parallelized by USACE-ERDC for execution in a distributed memory environment. Requirements: Your own computer with the latest version of the Watershed Modeling System (WMS) software installed. This software can be downloaded from You will be provided with information to license WMS at the start of the course. You can download the tutorials here: These materials will also be available at the course. Fees, access, other: The course is offered free of charge by dedicated civil servants, just trying to make it great. The course is taught at the Hydrologic Engineering Center, 609 Second Street, Davis, CA. PDHs are awarded based on contact hours. There are 30 possible contact hours. Information: For information about the course contact: Charles W. Downer For local Davis, CA information contact Dr. Billy E. Johnson Schedule: The basic course is three days, followed by a one day artic hydrology section. The afternoon of Day 3 is comprised of extensive training on sediment transport, including new in-stream sediment transport features in GSSHA. Day 1 – Introduction to GSSHA and Building a Basic GSSHA Model with the Hydrologic Wizard Day 2 - GSSHA Model Applications Day 3 - GSSHA Advanced Topics Morning – Groundwater Afternoon – Sediment transport Day 4 – Artic Hydrology A detailed itinerary follows. DETAILED SCHEDULE Day 1 Tuesday, April 11. Introduction to GSSHA and Building a Basic GSSHA Model with the Hydrologic Wizard Start Finish Duration Activity Topic 08:30 08:45 15 Greeting Introduction of Instructors/Attendees 08:45 09:30 45 Lecture Introduction to Hydrologic Modeling – Presentation 1 09:30 10:15 45 Lecture Introduction to GSSHA – Presentation 2 10:15 10:30 15 Break 10:30 10:45 15 Lecture WMS overview using digital spatial data Presentation 4 10:45 11:00 15 Lecture Images and projections – Pres 5 11:00 11:25 25 Workshop WMS basics and images – Tutorial 40 through 7 11:25 12:00 30 Demo Using the WMS Hydrologic Model Wizard 12:00 13:00 60 Lunch 13:00 13:20 20 Lecture Watershed delineation using DEMs – Presentation 7 13:20 13:40 20 Lecture Overland flow modeling in GSSHA – Presentation 8 13:40 13:50 10 Lecture Basic model setup in WMS – Pres 9 13:50 14:10 20 Workshop Basic model setup with WMS with the Hydrologic Wizard - Tutorial 47 sec. 8 14:10 14:40 30 Lecture Stream routing – Presentation 12A 15:40 14:55 15 Lecture Assigning channel properties with WMS – Presentation 12B 14:55 15:10 15 Break 15:10 15:30 20 Workshop Adding streams to your model with the Hydrologic Wizard – Tutorial 47 Sec. 9 15:30 15:45 15 Lecture Developing index maps with spatial data - Presentation 10 15:45 16:15 30 Lecture Modeling infiltration – Pres 11A 16:15 16:25 10 Lecture Using WMS to develop infiltration inputs – Presentation 11B 16:25 16:45 20 Workshop Adding overland processes to your model using the Hydrologic Modeling Wizard – Tutorial 47 Section 10-16 16:45 17:00 15 Recap of 1st day Day 2, Wednesday, April 12, 2017 GSSHA Model Applications Start Finish Duration Activity Topic 08:00 08:15 15 Lecture Distributed rainfall – Presentation 14B 08:15 09:15 60 Workshop Distributed rainfall – Tutorial 49 09:15 09:30 15 Break 09:30 09:45 15 Review Distributed rainfall 09:45 10:15 30 Lecture Hydraulic structures and embankments – Presentation 15 10:15 10:30 15 Lecture Using WMS to develop land-use change scenarios – Pres 17 10:30 12:00 90 Workshop Land use change – Tutorial 50 & 51 12:00 13:00 60 Lunch 13:00 13:45 45 Lecture Continuous simulations - Pres 18 ABC 13:45 14:45 60 Workshop Continuous simulations – Tutorial 52 14:45 15:00 15 Review Continuous simulations 15:00 15:30 30 Lecture Flood inundation modeling – Pres 20&21 15:30 15:45 15 Break 15:45 16:45 60 Workshop Flood inundation modeling – Tut 55 Day 3, Thursday, April 13, 2017 GSSHA Advanced Topics Start Finish Duration Activity Topic 08:00 08:45 45 Lecture Groundwater Modeling Fundamentals 30 08:45 09:15 30 Lecture Groundwater Modeling in GSSHA 31 09:15 10:00 45 Lecture Using WMS to develop groundwater model inputs - Pres 32 10:00 10:15 15 Break 10:15 11:15 60 Workshop Basic Groundwater Modeling – Tut 59 11:15 12:15 60 Workshop Surface groundwater interaction – Tut 60 12:15 13:30 75 Lunch 13:30 14:00 30 Lecture Sediment Transport – Pres 21 14:00 14:15 15 Lecture Sediment Transport Interface – Pres 21A 14:15 15:00 45 Workshop Sediment Transport – Tutorial 53 15:15 15:30 15 Break 15:30 16:00 30 Lecture In-stream sediment transport 16:00 16:45 45 Workshop In-stream sediment transport 16:45 17:00 15 Lecture Additional resources – Presentation 23 Day 4, Friday April 14, 2017 Arctic Hydrology Start Finish Duration Activity Topic 08:00 08:30 30 Lecture Arctic 1 - Continuous simulations with snow – Pres 19 08:30 09:15 45 Workshop Arctic 1A - Continuous simulations with snow - Tutorial 64 09:15 09:45 30 Lecture Simple frozen soil options in GSSHA 09:45 10.00 15 Break 10:00 10:30 30 Workshop Simple frozen soil options in GSSHA 10:30 10:50 20 Lecture Soil thermodynamics modeling theory 10:50 11:20 30 Lecture Modelling effects of frozen soil and hydrological dynamics in permafrost regions 11:20 12:20 60 Workshop Simulation of frozen soils and hydro -Simulating soil temperature profile. -Active layer hydraulic conductivity. -Watershed discharge. 12:20 13:30 70 Lunch 13:30 14:00 30 Discussion Simulation of frozen soils and hydro
  12. Here is some further information about this GSSHA course. If you cannot attend the course, you can attend via the teleconference link as shown below: VTC – The course will be broadcast via internet and teleconference. Information is below: Meeting Number: 8774119748 Code: 1445950 Teleconference Phone Number: 1-877-411-9748 Access Code: 1445950 Pass Code: 3803
  13. Long, Let me know how things go. Thanks, Chris
  14. Long, I don't have any suggestions other than trying to fix the sharp transitions in channel geometry by making sure your channel cross sections represent the actual channel bathymetry. What is the resolution of the DEM you're using to extract the cross sections? Are the channel bottom elevations represented in the DEM? If not, maybe you can modify the cross sections extracted from the DEM to include an approximation of the actual channel cross section as well as the channel thalweg. If your model runs with the same cross sections assigned to the nodes of your links, this tells me that the instability is introduced from the different cross sections at each node of your stream network. You could try decreasing your number of nodes/cross sections in your model by merging the arcs in your GSSHA coverage. Alternatively, you could try making some of the cross sections closer together where there are sharp transitions, changes in slope, or abrupt changes in Manning's roughness. I think it's just a matter of trial and error from here. You could also try sending your model to Chuck Downer and see if he replies and has any input. He would be interested in getting the model working better for your case. Hopefully this helps, Chris
  15. Naglaa, Your DEM probably has over 30 million cells, which is probably too many cells to run in TOPAZ. I'd run your model using TauDEM using the parallel processing (Use MPICH2") option. If you have a powerful computer with lots of memory and processors, that would be the best option for running TauDEM. You need to select the button to register MPIEXEC your computer if this is your first time running this option. You can select the default for the number of processors (4) or you can enter the number of processing cores on your computer, which I think is anywhere from 4 to 8 on computers nowadays. Hope this helps, Chris
  16. David, The depressions are retained on the DEM and in your model after running TOPAZ. The purpose of TOPAZ, when used with WMS, is to find the areas of high flow accumulation in your watershed. WMS can then determine stream locations from these accumulation values. TOPAZ itself does change your elevations to accomplish its purpose, but the DEM elevations in WMS are not changed. So because of this, TOPAZ may actually create areas of high flow accumulation (streams) that do not actually exist in a landscape like the one you are working on. You can always edit the streams created by WMS to more accurately represent aerial photograph or topographic map data for your area. So the answer to your question is that no, TOPAZ does not change your elevation data in WMS, but the flow accumulation values and stream network generated from running TOPAZ may not represent what actually happens in your watershed. The elevation values on your grid are changed when you run the "Clean Digital Dams" command from the GSSHA menu on your 2D Grid. This is when your depression polygons are used to define which elevation values you don't want changed. You can be certain any elevation values on your 2D Grid inside depression polygons are not changed, and you can confirm this by turning on the option to display Digital Dams in the 2D Grid display options. GSSHA takes significantly longer to run when you have lots of depressions like you have, but if this is what you're trying to do, the extra time is probably worth it to you. Hope this helps, you might want to contact Cody Alberts here at Aquaveo. He has had some experience in modeling areas with lots of depressions like yours using GSSHA. Let me know if I can help with anything else. Chris
  17. David, There's not a specific tutorial that describes how to maintain depressions to WMS. But you should be able to use your polygon shapefile to define your depressions fairly easily. You need to make sure you're using the most recent version of WMS on our web site since there was a bug in a recent release of WMS. Setup your basic model, but don't run the cleandam program until you've added your depression polygons. Here is what you do (after you have defined your initial model): 1. Read your polygon shapefile using File | Open. 2. Make sure the GSSHA coverage you're using with your model is the active coverage by selecting it. Go to the GIS Module. Select Mapping | Shapes->Feature Objects. Select Yes to convert all your shapefile data to map data. Step through the wizard to convert your data. Don't worry about mapping any attributes. 3. Go to your GSSHA coverage, which should now contain your shapefile polygons. Select the select polygon tool and select all your depression polygons. Select Feature Objects | Attributes and change the polygon type to "Depression Mask". 4. You should now be able to continue building your model and run the "cleandam" program before running GSSHA. The cleandam program is accessed from the GSSHA menu in the 2D Grid module (Clean Digital Dams) or from the Hydrologic Modeling Wizard (the Clean Up Model step). There's a display option to show digital dams in the 2D Grid Data display options. The digital dams inside your depression polygons should be maintained after running cleandam and the other digital dams should be removed. There are actually some WMS tutorials on our web site that have some discussion of digital dams. A tutorial you might be interested in going through is called "Updating a GSSHA Model using the MWBM Wizard" and can be accessed by going to our tutorial page here and clicking on the Distributed Hydrology tutorial tab. I hope this helps, Chris
  18. Long, Yes, I'd say if there are sharp transitions between adjacent cross sections of your channel you could get some model stability problems. I don't know if it is feasible, but could you try changing all your channels to just use trapezoidal cross sections? Then you could work on adding the natural cross section information once you get the trapezoidal cross sections running with the OVERBANK_FLOW option. Maybe you could save your modified model to a different folder. Another thing you should check is your stream thalweg elevations in relation to your grid cell elevations that intersect your stream. The grid cell elevations should be approximately the same as your TOB elevations. You can check and edit these elevations in the WMS Map Module under the GSSHA | Smooth Stream/Pipe Arcs menu item. Check your GSSHA summary file (.sum) to see if there are any warnings you're overlooking when you run your GSSHA project. If you check these things and make sure your cross sections have fairly smooth transitions and you're still having trouble getting a stable GSSHA model, you could contact Chuck Downer. He is the main GSSHA programmer and he should be able to help you if you send him your model and the specific issue you're having. His email address is on the main page. I hope this helps, Chris
  19. Long Yang, Yes, the model picks the largest Y values in the XY series as the TOB for natural channels. I'm not sure what you're asking in the second part of your question, but unless you have the OVERBANK_FLOW option defined, any water in your channel will stay in your channel when the depth exceeds the TOB. In this case, the model uses linear extrapolation to determine the channel elevations beyond the given channel geometry data. You will get a warning in the GSSHA summary file if this happens. Hope this helps, Chris
  20. Yanglong, After a little bit of looking around, I found the following description on this page: "The top of bank (TOB) is defined as the thalweg elevation plus the stream depth. For trapezoidal channels the user specifies the stream depth and the thalweg elevations [this is the "depth" parameter in WMS]. For natural cross sections TOB is taken from the XY point series inputs." I hope this helps, Chris
  21. Yanglong, I think the top of the bank is determined from the elevation of the cell through which the stream travels, but I'm not completely sure about this. There is a channel Depth parameter that's defined in GSSHA, but I don't know if this is used to determine the top of the bank. I'll need to check into this more and get back with you. If the OVERBANK_FLOW option is on, flow from the channel to the overland flow cells occurs if the water surface elevation in the channel is higher than the water surface elevation on the overland flow cells. I'll see what I can figure out and get back with you about this. Chris
  22. Denise, In your Elevation-Area table, is your minimum elevation value 1278 or less? It needs to be so HMS has enough information to route the flow through the detention basin since your outlet is at 1278. So check your table and make sure the minimum elevation is 1278 or less. If it is not, you should be able to manually change the value. This may or may not solve your problem, but it's something you should look at. There are lots of input parameters when defining a detention basin; it could be a problem with one of your other parameters also. Chris
  23. Ayman98, You don't need to worry about that error message. The model checker shows errors in the HEC-1 model and not in the HMS model. For most things, these models are the same but if you're using the frequency storm they're not the same. Go ahead and save and run your HMS model and it should work fine. Chris
  24. JCR, Are you defining the downstream boundary condition as an overland flow boundary condition? You probably can remove that downstream boundary condition; it's not needed and probably won't do anything. If you only have a single upstream variable flow boundary condition, the hydrograph at the downstream end of your model should match this upstream boundary condition after the time it takes for the water to arrive at this location. You should check a couple of things in your model. First, make sure your stream arc is defined as either a trapezoidal or a cross section channel. This tells GSSHA that you want to run the 1D Hydraulic model for this cross section and the depths and flows will be computed along the length of the stream and your upstream boundary condition will be used. Second, make sure you turn on the option in the GSSHA Job Control dialog to run Diffusive Wave routing (No routing is the default). Finally, make sure you don't have any adverse slopes along your stream. You do this by selecting the arcs along the length of your stream and then Smoothing the streams along these arcs using the option in the GSSHA menu at the top of the WMS window. Doing these things should improve stability. Make sure you select the Model Checker command in the GSSHA menu in the 2D Grid module and fix any errors or warnings that show up. You can also decrease your time step to 2 seconds, but I don't think this will fix the problem you're having. I hope this helps. Let me know how things go with your model. Chris
  25. Something strange is going on with your model. Normally, Total flow = Direct flow + Baseflow and the numbers do not add up for your model. Also the (Excess * Basin Area * unit conversion factors) should = Direct flow. Are you getting any warnings when your run your HMS model? If so, what are they? What kind of model are you running? Is it a ModClark simulation? If you contact technical support they may be able to help you. Chris