From Gsshawiki
Jump to: navigation, search

The basic process used in WMS to create a grid is to first delineate the watershed boundary and streams from a DEM and convert the results to a bounding polygon for the watershed. This bounding polygon is then “filled” with grid elements of the appropriate size for the planned simulation, and elevations for grid cell centers are interpolated from the original DEM. WMS provides multiple options for creating the bounding polygon, but the recommended method is to use a DEM. WMS supports both USGS file formats as well as Arc/Info ASCII grid files.

The size of grid cells used for a GSSHA simulation will vary depending on the area of the watershed and objectives of the simulation, as well as computing resources. Inevitably some of the grid cells will need to have elevations adjusted to create more “natural” and numerically stable overland flow. There are a few options in WMS to help identify and mitigate problem cells. The need to edit grid cells is most easily identified by running a basic simulation to examine areas on the grid that pond excessively. Setting up and running a basic simulation is the content of the next chapter.

Related Topics

GSSHA Wiki Main Page
Primer Main Page

Obtaining DEM data for watershed delineation
Watershed delineation
Grid sizes
Constructing a grid