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How does flow accumulation work?
The Flow Accumulation tool calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. If no weight raster is provided, a weight of 1 is applied to each cell, and the value of cells in the output raster is the number of cells that flow into each cell.
What is a pour point in watershed?
A watershed is the upslope area that contributes flow—generally water—to a common outlet as concentrated drainage. The outlet, or pour point, is the point on the surface at which water flows out of an area. It is the lowest point along the boundary of a watershed.
What do I need to know about r.watershed?
If no map or value is given, r.watershed assumes no disturbed land. This input is used for the RUSLE calculations. Option blocking specifies terrain that will block overland surface flow. Blocking cells and streams stop the slope length for the RUSLE.
Which is the default flow direction in r.watershed?
Flag -s force the module to use single flow direction (SFD, D8) instead of multiple flow direction (MFD). MFD is enabled by default. By -4 flag the user allow only horizontal and vertical flow of water. Stream and slope lengths are approximately the same as outputs from default surface flow (allows horizontal, vertical, and diagonal flow of water).
Which is better r.terraflow or r.watershed?
Thus, if forest canopy exists in valleys, SRTM, IFSAR, and similar data products will cause major errors in r.terraflow stream output. Under similar conditions, r.watershed will generate better stream and half_basin results.
What kind of search algorithm does are watershed use?
Since the S factor is a small number (usually less than one), the GRASS output map is of type DCELL. r.watershed uses an A T least-cost search algorithm (see REFERENCES section) designed to minimize the impact of DEM data errors.