# D8 Distance To Streams

(c) 2010 by David G. Tarboton
Computes the horizontal distance to stream for each grid cell, moving downslope according to the D8 flow model, until a stream grid cell is encountered.

## Parameters

Number of Processes
Integer
  The number of stripes that the domain will be divided into and the number of MPI parallel processes that will be spawned to evaluate each of the stripes.
D8 Flow Direction Grid
Raster Grid
  This input is a grid of flow directions that are encoded using the D8 method where all flow from a cells goes to a single neighboring cell in the direction of steepest descent. This grid can be obtained as the output of the "D8 Flow Directions" tool.
Stream Raster Grid
Raster Grid
  A grid indicating streams. Such a grid can be created by several of the tools in the "Stream Network Analysis" toolset. However, the tools in the "Stream Network Analysis" toolset only create grids with a value of 0 for no stream, or 1 for stream cells. This tool can also accept grids with values greater than 1, which can be used in conjunction with the Threshold parameter to determine the location of streams. This allows Contributing Area grids to be used to define streams as well as the normal Stream Raster grids. This grid expects integer (long integer) values and any non-integer values will be truncated to an integer before being evaluated.
Threshold
Double
  This value acts as threshold on the Stream Raster Grid to determine the location of streams. Cells with a Stream Raster Grid value greater than or equal to the Threshold value are interpreted as streams. Default value 50.

## Outputs

Distance to Streams
Raster Grid
  A grid giving the horizontal distance along the flow path as defined by the D8 Flow Directions Grid to the streams in the Stream Raster Grid.