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Flow Distance function

Available with Spatial Analyst license.

Overview

For each pixel, the function will calculate the minimum downslope horizontal or vertical distance to pixel(s) on a river or stream into which they flow. If an optional flow direction raster is provided, the down slope direction(s) will be limited to those defined by the input flow direction raster. The output is a flow distance raster.

Notes

To limit downslope directions along which minimum flow distance is measured, provide an optional input flow direction raster that can be derived using the Flow Direction function. Choose from D8, D-Infinity (DINF) and multi-flow direction (MFD) flow models while generating an optional input flow direction raster.

If an optional input flow raster is provided, it is recommended that his raster be created using the Flow Direction tool using the same input surface raster that you will provide to the Flow Distance function.

  • If this input surface raster is void of sinks, the distance measurements would be to stream pixels represented by the input stream raster.
  • If this input surface raster has sinks present, some flow paths can get terminated prematurely by flowing into sinks before reaching streams. In such cases, flow distance measurements for these pixels are calculated only up to the sinks into which they flow.

When the function is run without providing an optional flow direction raster, minimum flow distance is assessed considering all possible downslope flow paths from each pixel to pixels on a stream into which they flow. When the function is run with a D8 flow direction raster, there is only one possible downslope flow path from every pixel to a pixel on the stream, and flow distance is measured along this single flow path.

It is recommended to create the input stream raster using the same input stream raster that is provided as an input to the function. You can create stream rasters from an input surface raster using the Flow Direction, Flow Accumulation, and Con functions respectively. If you wish to use streams from other data sources, for best results, convert them to the input surface raster first then run the Flow Distance function on the result.

Parameters

ParameterDescription

Stream Raster

An input stream raster that represents a linear stream network.

Surface Raster

The input raster representing a continuous elevation surface.

Flow Direction Raster

The input raster that shows the direction of flow out of each pixel.

When a flow direction raster is provided, the down slope direction(s) will be limited to those defined by the input flow directions.

The flow direction raster can be created using the Flow Direction function.

Distance Type

Determines if the vertical or horizontal component of flow distance is calculated.

  • Vertical—The flow distance calculations represent the vertical component of flow distance from each pixel in the domain to the pixel(s) on the stream into which they flow. This is the default.
  • Horizontal—The flow distance calculations represent the horizontal component of flow distance from each pixel in the domain to the pixel(s) on the stream into which they flow.

Licensing

This function requires that the ArcGIS Spatial Analyst extension to be enabled.