This task can be accomplished with the Con tool or using Map Algebra. Flow accumulation outputĪ threshold can be specified on the raster derived from the Flow Accumulation tool the initial stage is defining the stream network system. The output flow direction raster created in a previous step is used as input. To create a stream network, use the Flow Accumulation tool to calculate the number of upslope cells flowing to a location. However, if you want to calculate only the stream network, this step can be ignored. Using the Watershed tool, the watersheds are delineated for specified locations. To ensure proper drainage mapping, these depressions can be filled using the Fill tool. The depressions shown in the graphic above (the scattered colored points) are problematic because any water that flows into them cannot flow out. A sink is usually an incorrect value lower than the values of its surroundings. With the Sink tool, any sinks in the original DEM are identified. Using the DEM as input to the Flow Direction tool, the direction in which water would flow out of each cell is determined. The DEM on which the hydrologic analysis will be performed. The following graphics illustrate the steps involved in calculating a watershed and stream network from a DEM. Using an elevation raster or digital elevation model (DEM) as input, it is possible to automatically delineate a drainage system and quantify the characteristics of the system.
The image below is of a resulting stream network derived from an elevation model: Example stream network derived from elevation model The hydrologic tools allow you to identify sinks, determine flow direction, calculate flow accumulation, delineate watersheds, and create stream networks. The hydrologic modeling tools in the ArcGIS Spatial Analyst extension toolbox provide methods for describing the physical components of a surface.
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