lclements

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About lclements

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  1. All If I wanted to model a large river channel and floodplain using 2D only, how would people go about including the river channel bathymetry into the DTM? LiDAR will provide the terrain data, but will poorly-define the river channel itself. Is there a way to use channel cross section data to modify the base DTM to reflect the surveyed channel? We have regular channel cross-sections, and would like to use this data to 'carve' a more detailed channel through the DTM. The method will need to account for any meanders etc... Are there clever ways to do this in Arc/MapInfo/QGIS? Any pointers gratefully received :-)
  2. Hi Phil, Yes I do mean depth varying Manning's n.... Cheers, L
  3. All, We are running a rainfall model using TuFLOW, which uses variable Manning's for the 2D domain to help maintain model stability. However, the thought occurred as to why it is not more common to incorporate variable Manning's into all models? Is this something that people have given much thought to, or is a constant Mannings roughness value considered to be appropriate? Any thoughts would be most welcome. Regards, L
  4. Dear all, I am modelling a circular culvert and trying to understand the relevant form loss coefficients and inlet/outlet losses. Specific queries are: - How would I best represent a trash screen on the upstream face of a circular culvert? - Is it best to account for bends along a culverted length using increased Mannings or a form loss coefficient? - What are appropriate form loss values? There appears to be limited guidance in the literature regarding losses at culverts- is there any particularly relevant guidance that may be of benefit to me? Thanks! :-)
  5. Dear all, I have tried to convert a GEOTIFF from QGIS into ASCII format for reading directly into the tgc. However, I get the following error message: ERROR 2333 - Insufficient header information in external grid file. Check format of file. I have tried to use the asc_to_asc conversion, and have also checked that QGIS is not converting the data into Golden Surfer format. Are there any other reasons why Tuflow cannot handle the ASCII? Any pointers gratefully received. Regards, Laura