This tool can be used to calculate the elevation of each grid cell in a raster above the nearest stream cell, measured along the downslope flowpath. This terrain index, a measure of relative topographic position, is essentially equivalent to the 'height above drainage' (HAND), as described by Renno et al. (2008). The user must specify the name of an input digital elevation model (`dem`) and streams raster (`streams`). The DEM must have been pre-processed to remove artifact topographic depressions and flat areas (see breach_depressions_least_cost). The streams raster should have been created using one of the DEM-based stream mapping methods, i.e. contributing area thresholding. Stream cells are designated in this raster as all non-zero values. The output of this tool, along with the downslope_distance_to_stream tool, can be useful for preliminary flood plain mapping when combined with high-accuracy DEM data.

The difference between elevation_above_stream and elevation_above_stream_euclidean is that the former calculates distances along drainage flow-paths while the latter calculates straight-line distances to streams channels.

## Reference

Renno, C. D., Nobre, A. D., Cuartas, L. A., Soares, J. V., Hodnett, M. G., Tomasella, J., & Waterloo, M. J. (2008). HAND, a new terrain descriptor using SRTM-DEM: Mapping terra-firme rainforest environments in Amazonia. Remote Sensing of Environment, 112(9), 3469-3481.

## See Also

elevation_above_stream_euclidean, downslope_distance_to_stream, `ElevAbovePit`, breach_depressions_least_cost

## Function Signature

`def elevation_above_stream(self, dem: Raster, streams: Raster) -> Raster: ...`

## Project Links

WbW Homepage User Manual Support WbW