Downslope index (radius)

This tool can be used to calculate the downslope index described by Hjerdt et al. (2004). The downslope index is a measure of the slope gradient between a grid cell and the nearest downslope location that represents a specified vertical drop (i.e. a potential head drop). The index has been shown to be useful for hydrological, geomorphological, and biogeochemical applications. In contrast to the Downslope index tool, which is searching for downslope cells in the D8 flow direction, the Downslope index (radius) tool is searching for downslope cells within a specified radius.

The user must specify:
The name of the input digital elevation model (DEM)
The name of the output grid
The head potential drop (d)
The maximum search radius
The output type. This can be either 'tangent', 'degrees', 'radians', or 'distance'.
Whether the lowest elevation should be used in case no elevation with distance d can be found within the specified radius.

Grid cells containing NoData values in any of the input images are assigned the NoData value in the output raster. The output raster is of the float data type and continuous data scale.

Reference:

Hjerdt, K.N., McDonnell, J.J., Seibert, J. Rodhe, A. (2004) A new topographic index to quantify downslope controls on local drainage, Water Resources Research, 40, W05602, doi:10.1029/2004WR003130.

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