Sunday, 4 December 2016

raster - How to build an artificial 'dam' across a river?


I have a DEM. Created all files related to watershed including accumulation, direction, streams etc... I'm stuck creating a dam. I request you to please let me know how to build an artificial 'dam' across a stream/river.


Please suggest any software/methods to do.




Answer



Well, the "de facto" way of doing it, if I understood you correctly (you want to modify a DEM to contain the dam and it's lake) you will need to create a separate DEM just for the dam.


The way to do it is to use a flat DEM with the height of your lake. Create a constant DEM. It cannot be a rectangular DEM, it must have the shape of the lake contour.


http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=Create_Constant_Raster


After that just replace the values on the original DEM that intersect your lake polygon by this constant DEM. It should provide you with a flat area surface DEM containing your lake.


In this step you will need a polygon,with the lake shape. Convert it to Raster and make it constant (with the value of lake height). Then you can easily replace the values on the old dam (do not sum the values, otherwise you will have just heightened the terrain) using map algebra tools.


http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=Single_Output_Map_Algebra


To model the actual dam, i would suggest another software, as Google SketchUp.


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