This tool can be used to divide a landscape into a group of nearly equal-sized watersheds, known as isobasins. The user must specify the name (`dem`) of a digital elevation model (DEM), the output raster name (`output`), and the isobasin target area (`size`) specified in units of grid cells. The DEM must have been hydrologically corrected to remove all spurious depressions and flat areas. DEM pre-processing is usually achieved using either the breach_depressions_least_cost or fill_depressions tool. Several temporary rasters are created during the execution and stored in memory of this tool.

The tool can optionally (`connections`) output a CSV table that contains the upstream/downstream connections among isobasins. That is, this table will identify the downstream basin of each isobasin, or will list N/A in the event that there is no downstream basin, i.e. if it drains to an edge. Additionally, the CSV file will contain information about the number of grid cells in each isobasin and the isobasin outlet's row and column number and
flow direction. The output CSV file will have the same name as the output raster, but with a *.csv file extension.

## See Also

watershed, basins, breach_depressions_least_cost, fill_depressions

## Function Signature

`def isobasins(self, dem: Raster, target_size: float, connections: bool = False, csv_file: str = "" ) -> Raster: ...`

## Project Links

WbW Homepage User Manual Support WbW