A Subbasin represents the drainage catchment that receives rainfall during a storm event. In hydrology, a subbasin is used to represent the physical watershed.
A watershed could be defined as an area of land that drains all the streams and rainfall to a common outlet such as the outflow of a reservoir, mouth of a bay, or any point along a stream channel. The word “watershed” is sometimes used interchangeably with drainage basin or catchment.
Commands for Generating Subbasins
There are several commands available in GeoHECHMS which allow the user to draw subbasins manually or automatically on the Map View. Some of the commands work only in the US.
Delineate Subbasins Command
This command uses the project’s local DEM gridded elevation data for the delineation process. It works globally and allows the user to automate the subbasin delineation process. Refer to this article in our knowledge base to learn about how to use this command.
Delineate Watershed Command
This command uses the USGS WMS (Web Map Service) service and the NED (National Elevation Data) to automate the watershed delineation process. It computes the contributing watershed drainage network that drains to a selected map location (outlet point) on the Map View. Refer to this article in our knowledge base to learn about how to use this command.
USGS StreamStats Command
This command works only in the US. It allows the user to click on a stream location in the Map View, prompting the software to delineate the watershed basin boundary, compute the basin characteristics, and provide estimates for flow based upon site-specific USGS regression equations. The software will generate GIS shapefiles containing the determined watershed boundary and basin characteristics, stream flow path, as well as PDF results report for the selected site. Refer to this article in our knowledge base to learn about how to use this command.
Draw Subbasins Command
This command allows the user to interactively draw polygons on the Map View as subbasins. After drawing subbasins, the user can name individual subbasins with a unique ID. Refer to this article in our knowledge base to learn about how to use this command.