GIS for Watershed Modeling Exercise II

At the dialog that appears select your output raster (elev )as the input surface and select the output in Degree or Percent. You will get something like the following:


You can make the slop raster permanent by right click the layer slope of elev, then select Make Permanet:


Calculating Aspect:

Select Spatial Analyst -> Surface Analysis -> Aspect on the Spatial Analyst toolbar. At the dialog that appears select elev as the input surface.



Calculate Flow Direction

-- Assign a flow direction to each grid cell based on the neighboring cell with the lowest elevation
Open the Toolbox (not the spatial Analysis tool bar). Open ArcToolbox, select Spatial Analyst Tools -> Hydrology -> Flow Direction, double click on Flow Direction



Select elev as the input raster and specify names for output rasters (e.g. FlowDir).


Here is the Flow Direction grid:


Compare the result with your hand drawing on the flow direction grid.

Calculate Flow Accumulation


• Flow accumulation is calculated from flow directions.

• It calculates the number of grid cells drain into an individual grid cell.

With ArcToolbox open, select Spatial Analyst Tools -> Hydrology -> Flow Accumulation, double click on Flow Accumulation


to be continued
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