You may want to use an alternative to the Fill Sinks operation in ArcHydro that generates more realistic flowpaths in flat regions. This is "Fill Sinks Plus". This is a Customized Command or button that can be installed in ArcMap 10.1 by using the ArcObjects.NET as distributed by ESRI. The installation of this button is detailed in http://www.lago-consulting.com/fill_sinks_plus.html. I hope this help. I'm trying to use ArcHydro to find watersheds and flow patterns in an urban area within a river's floodplain. Within the district scale site there is a large, flat area where water collects (this urban district is surrounded by levees, so water flows and collects in this specific area). This is my specific area of study. When I use the Fill Sink tool, it makes the entire area one color as if there is no elevation change. When I use the Flow Direction tool on the incorrect Fill Sink raster, the Flow Direction output has the proper color directions (1,2,4,8,16,32,64,128) but still shows the area as completely flat. If I run the Fill Sink tool on the DEM again, but this time with a Threshold value of 1, the output Fill Sink shows true elevation differences within the area. However, when I use the correct-looking Fill Sink raster in a Flow Direction tool, a correct-LOOKING Flow Direction raster appears but with values 1-255. I cannot move forward with this correct-looking data with the wrong values. Does anyone know how to get to Flow Direction to output the correct elevation differences?
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