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cameronParticipant
The simple answer is that the wse is getting higher than the HTAB value and needs to be increased.
The real question would seem to be why is your model going unstable at those particular cross-sections to cause bad results?
There could a lot of different reasons and varies for each model so we would need more information.
January 31, 2020 at 6:35 pm in reply to: Raising / lowering cross sections from the inversion elevation #12717cameronParticipantI am a little confused to what you want. You don’t want to raise/lower the entire cross-section. You don’t want to raise/lower a section of the channel. Both of these would modify your invert.
The invert of your cross-sections are based on the the lowest point between bank stations. Are you saying you only want to adjust that single point? If you were to only adjust that single point, it may not be the invert anymore if it was raised above another point in the channel.
The channel modification tool can use a generic template or an actual cross-section as the template. You can specify a slope or elevation for it to develop the invert profile you want at the spacing you wanted. You can also control how much of a cross-section changes, either all of it or only what is in the channel.
January 31, 2020 at 2:50 am in reply to: Raising / lowering cross sections from the inversion elevation #12715cameronParticipantYou can use the Channel Design/Modification tool
cameronParticipantReach out the HEC about it. Contact information is on their website.
January 30, 2020 at 6:54 pm in reply to: HEC-GeoRas – Errors during “Floodplain delination Using Rasters” #12710cameronParticipantA couple things going on. First, both Mapper and HEC-GeoRAS create “wse tins” and just apply it to the terrain you provide. The wse tins are based on the cross-sections extents and cover the entire cross-section unless you put a levee feature in the cross-section which it then clips the “tin” to that point.
Second, in the 1D HEC-RAS model, it has no idea if areas should be connected or not. All it does is a calculation based on the shape of your cross-section. This is where understanding limitations of models is important. 2D would more detailed so if you set the model up correctly, it would know if areas should be connected or not.
Not sure what the purpose of your study is for, but if you don’t think water can get to a certain location, I would either put a levee feature there or trim the cross-section shorter. If you are running multiple flows (low and high) where the high flow does get out there, you would have to set the levee elevation just above the low flow wse and below the high flow wse.
If it is for FEMA, they won’t allow a levee feature unless it really is a levee and so you would just have to make it ineffective and then clean it up in GIS.
cameronParticipantYou would have to have a gap between the two connections of at least 1 grid cell I believe. You would connect the upstream end of the channel to the 2D one way and then use lateral structures for each side.
The figure below shows a crude example
cameronParticipantI would use the channel modification tool where you could just enter in the slope you want.
cameronParticipantare you running the model on the network or local machine? Try deleting the hdf file and then running again.
cameronParticipantI would as you mentioned try and fix the model to remove the high velocities by either adjusting grid cells, timestep, or roughness values first.
The results you are showing are at the specified mapping interval you set so it won’t pick up the max values unless they occur at the specified mapping interval.
If you want to just get the max value from the mapping interval, I would use a python script to extract it from the hdf file. If you don’t know scripting, you could set up the program in Mapper to write the output you want (wse, vel, depth, etc..) for every every mapping interval as a raster and then in ArcMap you the mosaic tool to take the max value from all of them.
cameronParticipantDid you try the Bing Maps? I have seen this happen occasionally with Google Maps.
cameronParticipantThe default in the model is set to energy gradeline. This basically makes the bridge think that the energy gradeline is the wse and causes pressure flow.
The link below has some discussion on this in the comments section.
http://hecrasmodel.blogspot.com/2009/08/problems-with-bridges-and-culverts.html
EGL is used because of the conservative assumption that any disturbance in the flow (debris, etc.) could bring the HGL up to the EGL level. If you have a supercritical reach, or if you suspect that the HGL is so far under the deck that using the EGL is not appropriate, then change the pressure flow criteria. Its really just up to your own judgment.
cameronParticipantThere are python and vba code that can read the results. The “Breaking the HEC-RAS Code” book shows how to use the HEC-Controller.
cameronParticipantthe most efficient way would be to use python to read the HDF file to extract these values for you. You could also export the data to rasters and create a model builder in ArcMap if you don’t know python.
cameronParticipantThe program should project on the fly. Have you tried to bring it in using a different projection?
cameronParticipantYou would need to use HEC-GeoRAS.
What I would do though is use Mapper to export out the XS and other data as shp files.
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