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Everything posted by PM_2009

  1. Hi, I realised that my model actually seems to be working like "overland_backwater": the water does not go to the stream when the water level in the stream is higher than the grid/water surface on the grid, but the water does not come out of the channel either, even if I have "allow overbank flow" chosen in the job control. Any idea if there has been this kind of problems with gssha? If this problem were be caused by too high/low channel depth, which one would be more likely to cause this kind of problem (I have tried to define the streams so that the channel bank is about at the same level as the grid, but as the grid is not totally smooth, in some places the channel is "too shallow".) Grateful for any answer, as usual! Pirkko
  2. I have had the overbank flow mode on, but thanks for the answer! Do you know if it would make any difference to use ADE-PC (now using ADE) as overland flow computation method? Pirkko
  3. Hi, I have a question about relationship between the channel flow and the overland flow in GSSHA: In my simulation (overbank flow allowed) I have noticed that in a place, where water rises above the channel bank level and floods to the floodplain, the water level on the flood plain does not rise even close to the same level as the water level in the channel. The channel depth and thalweg elevations are such that the channel bank should be a few centimeters below grid elevation (but I have tried with the channel bank elevation above the grid elevation, with the same problem). The water level in the channel stays above the channel bank elevation (and overland water level) for about 9 days (the time step is 180 sec, max. flow in the channel is 8 m3/s). It seems that the overland water elevation starts to rise only after the channel water elevation has been above the grid elevation for two days or so. The max. overbank water elevation is about half a meter above the channel water elevation. It does not seem to make a difference if Manning’s coefficient on the floodplain is greater than in the channel. Infiltration rate is assumed to be very small. Any ideas why there seems to be this boundary between the channel and the floodplain (is this because the channel flow is calculated as 1D and the overland flow as 2D?) Is there any way to stop this from happening? I got the overland water elevations by adding the water depth on a cell to the grid cell elevation and the channel water level by adding the channel water depth to the node z-value , is this a correct way to get these elevations? Thanks again for any answers! Pirkko
  4. Hi, is there any estimations for soil infiltration parameters (to use in GSSHA) for peat land? I have only found some values for porosity and Ks in literature. thanks! Pirkko M.
  5. Hi, I'm using GSSHA in WMS 8.2. I was wondering what happens if I connect, for example, a trapezoidal channel with depth = 1.5 m to another trapezoidal channel with depth = 1m, and then use the "smooth stream arcs" so the channels are not running uphill at any point. Does the "smooth stream arcs" actually smooth the elevations of the banks of the channels, and does this mean that if a deeper channel connects to a shallow channel, the bottom of the channel goes half a meter up in the connecting point even when "the smooth stream arcs" show that the channels are smoothed? Another question i have is that if the channel runs, for example, a meter below the grid (because, as in the reality, the channel goes through "hills" where the elevation of the ground is something like two meters above the general ground elevation), does the model add a meter to the defined channel depth or what? What is the relationship between the grid and the channel in this kind of situation? What if the water in the channel rises above the defined channel bank but not higher than the grid surface? Thanks again for any answers! -Pirkko-
  6. hi, i'm having a problem with adding lakes and running the gshha then... Basically, the lake fills up, but then the water doesn't go out of the lake as discharge (in the end the lake is full but there is no discharge, longer total time doesn't change anything). I have tried different outlet structures, but they don't seem to make difference. (Btw, when there is a weir with a crest point elevation, is that elevation from the grid or the actual z-value i want for the crest? I assumed the latter, but tried the former too...) There is some flow out of the lake, but it's maybe a tenth of the flow into the lake, even at the highest peak. Is there something i have missed about connecting the lake to the outlet and the outlet to the channel? Should the embankment be connected to the channel leading out of the lake? I don't know if this is connected to this problem, but if I try to chance the attributes of the embankment after running GSSHA, WMS always crashes. thanks for any advise, -Pirkko-
  7. PM_2009

    Flat areas?

    Hi again, now I noticed that, after choosing "interpolate grid cell elevations to streams" box at 2D-grid creation, the 2D-grid has about 1 meter high banks around the streams (to keep the stream elevations below the grid?), and this stops the overland flow from reaching the stream and makes it pool in the places where two streams meet. Is there any way to stop this from happening, other than not choosing this interpolate grid cells- option? Related to this, is it normal that when I (before creating the 2d-grid) manually add streams to my stream network created from the TOPAZ accumulation data (there is some ditches in the area that don't show in the TOPAZ), I have to manually add the z-values: the z-values in the vertices and nodes are 0.00 when i first draw the streams? Because I think this might be part of the problem: I can't put enough vertices to the added streams for them to fit to the DEM perfectly -> stream elevations above the ground level. Thanks for any suggestions, again -Pirkko-
  8. PM_2009

    Flat areas?

    I used the hydrologic wizard to making interpolate the grid cell elevations to stream elevations and now water leaves as discharge, thank you, again!
  9. PM_2009

    Flat areas?

    Hi, I managed to get my GSSHA simulation run now with the diffusive wave channel routing, and the water doesn't pool on the surface. The problem is, the water seems to stay in the channels. I get the following summary file: volume of rainfall to overland: 696000.0 volume remaining on surface: 88271.4 final volume in channels (cu. m): 603714.1 volume of discharge: 5829.7 Total time is already set as 10000 minutes, so too short simulation time should not be a problem (I think?). Manning's roughness in channels is set to 0.05. I have smoothed the channels, and there should be no adverse flow. Still, in some places the channel slope is small. Is this why the water stays in the channel instead of leaving the area as discharge? Is there something I could do about this? Thanks!
  10. PM_2009

    Flat areas?

    Yes, I'm using GSSHA. I'll try the hydrologic modeling wizard, thanks!
  11. PM_2009

    Flat areas?

    hi, I am modelling a watershed (with wms 8.2), using a 25 m grid DEM. The problem is that, even after removing digital dams, the water doesn't seem to leave the area. In the summary file, it says that almost all of the rain is accumulated on the surface and almost none is going out of the area as flow. When I click the "depth" on, it seems that the places the water accumulate to are not always where the TOPAZ accumulation is shown. Also, the accumulated water doesn't leave through the streams (like it does in reality) even if the stream goes through the place of accumulation. My watershed area is very flat, there is quite a few flat dem cells too. When I run the TOPAZ, the streams don't go to exact places they are in reality. Is there anything I can do to make the water stop from accumulating on the surface? Would it help to define the streams as trapezoidal? Thanks! Pirkko
  12. Thank you, I used the hydrologic modeling wizard and it's working!
  13. Hi, is there a way in WMS 8.2 to restore all the settings back to the original without installing WMS again? Thanks for any ideas! -pirkko-
  14. Hi! I’m a newbie with the GSSHA and trying to run GSSHA simulation, but get nowhere with creating a 2D-grid with the Create Grid command. I’m using WMS version 8.2 I’m following instructions in http://www.gsshawiki.com/gssha/Tutorials:1...low_Model_Setup I have a 25 m resolution DEM, and I have run the TOPAZ, created the basin and stream arcs, and made a polygon from the basin. In Greate Grid window (after selecting the basin polygon), I have chosen a base cell size of 25m. Then I have chosen “interpolate from DEM” in the next prompt. Instead of even grid, I get grid with cells that are 25 m wide but 1287 m “tall”. When I try to run GSSHA (after defining precipitation etc.), I get error: “The grid size specified in the project file 24,…m differs from the north-south dimension of the raster grid cells 1287,… m as calculated from the Watershed_Mask header. Check your data to make sure they agree.” My DEM is of a very flat area, which has caused some problems before, but I don’t think the problem is with my DEM because I have the same problem when using DEMs from the tutorial file. Furthermore, I have managed to create the 2D-grid just fine from this DEM using WMS 8.1. Maybe there is something wrong with grid settings? I don’t remember touching any of the grid settings, but is there a way to return all settings to their original form? I would be most grateful for any help anyone could give! -Pirkko M.-
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