Chris Smemoe

WMS Development Team
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Chris Smemoe last won the day on March 1 2011

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About Chris Smemoe

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  1. Long, Let me know how things go. Thanks, Chris
  2. 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
  3. 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
  4. 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
  5. 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
  6. 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 gsshawiki.com page. I hope this helps, Chris
  7. 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
  8. 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
  9. 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
  10. 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
  11. 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
  12. 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
  13. 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
  14. Ayman98, Thanks for your questions. For information on injection or recharge wells, I recommend going through the Tutorial titled "Advanced Groundwater Modeling in GSSHA". The tutorial and the data associated with it can be downloaded under the Distributed Hydrology tab on this page. There is a section in this tutorial on adding wells to your groundwater model and you would just enter a negative pumping rate instead of a positive pumping rate as described in this section. Note that this tutorial has at least one prerequisite tutorial that describes how to define a basic groundwater model. For information about how to define a storage dam, you should go through the tutorial titled "Analyzing the Effects of Land Use Change (Part II)". This first part of this tutorial describes how to define a "Detention Basin", which is the same as a storage dam with possibly different outlet structures. You would probably define a rule curve in the detention basin parameters dialog. Note that this tutorial also has at least one prerequisite tutorial. Defining an artificial pond probably just takes some experience working with GSSHA. There are tutorials and help pages explaining some of the concepts, but there's not a single tutorial. The way I would define an artificial pond is to define depression polygons in a GSSHA coverage where the artificial ponds are located. There's a program called "cleandam" that you run after defining your GSSHA model that removes low points in your model by changing the elevations at these points. When you run cleandam, any grid cells inside depression polygons are ignored and the original elevations on these cells are maintained. So make sure the bottom elevations of the ponds are represented in your grid elevations, define depression polygons in your GSSHA coverage where your ponds are located, and run cleandam as usual and the elevations of your ponds will be maintained after running cleandam. GSSHA will then just use its normal overland flow and infiltration routines for these ponds when you run the model. Note that computation of overland flow with large ponds will require a smaller time step for your model. Hope this helps, Chris
  15. Yes, there are lots of ways of exporting the results from HEC-HMS. One way is to just go to the Results tab and select the node you want the results for, then select Time Series Table and copy/paste (Ctrl + C/Ctrl + V) the data from the table into a spreadsheet for plotting. You can also always screen capture the plots from HMS. There is also a custom reporting tool that uses a .xsl template file to create a report using HMS-computed data. When HMS runs a simulation, it creates a DSS file in the directory where your HMS model is stored. You can read this DSS file into HEC-DSSVue. HEC-DSSVue has several tools for plotting and creating reports from DSS files. That's all the ways I know of to get your results from HEC-HMS into other programs for creating reports. Chris