WMS:Compute Basin Data

When the drainage coverage feature objects are used to create a hydrologic model the area of the polygons can be determined and used in any of the supported hydrologic models. If the points/vertices used to create the feature arcs also have z values associated with them then WMS will make a rough estimate of the longest flow path and slope along such a path. Finally, if you have derived a watershed from feature objects, but have a background DEM you can compute most of the basin data parameters using the following steps:

1. Import/Read the DEM.
2. Compute the flow directions using TOPAZ.
3. Use the Polygon Basin IDs→DEM command found in the DEM menu in the Drainage module to assign DEM cells a basin id from the feature object polygons.
4. Choose the Compute Basin Data command from the Feature Objects menu of the Map module.

Of course, the results will only be approximate since the actual basin boundaries will not have been derived from the computed flow direction data, but it will provide a reasonable estimate. Ideally you will want to derive the basin boundaries from the DEM and flow direction data and then use the Compute Basin Data command in the DEM menu of the Drainage module.

Related Topics

• Feature Object Guidelines
• Computing Basin Data from DEMs
• Computing Basin Data from TINs