Flow Length (Spatial Analyst)

ArcGIS Pro 3.4 | | Help archive

Available with Spatial Analyst license.

Summary

Calculates the upstream or downstream distance, or weighted distance, along the flow path for each cell.

Usage

  • A primary use of the Flow Length tool is to calculate the length of the longest flow path within a given basin. This measure is often used to calculate the time of concentration of a basin. This would be done using the Upstream option.

    The tool can also be used to create distance-area diagrams of hypothetical rainfall and runoff events using the weight raster as an impedance to movement downslope.

  • The value type for the Flow Length output raster is floating point.

  • When the output raster format is .crf, this tool supports the Pyramid raster storage environment. Pyramids will be created in the output by default. For any other output format, this environment is not supported, and pyramids will not be created.

  • See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool.

Parameters

LabelExplanationData Type
Input flow direction raster

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

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

Raster Layer
Direction of measurement
(Optional)

The direction of measurement along the flow path.

  • DownstreamCalculates the downslope distance along the flow path, from each cell to a sink or outlet on the edge of the raster.
  • UpstreamCalculates the longest upslope distance along the flow path, from each cell to the top of the drainage divide.
String
Input weight raster
(Optional)

An optional input raster for applying a weight to each cell.

If no weight raster is specified, a default weight of 1 will be applied to each cell. For each cell in the output raster, the result will be the number of cells that flow into it.

Raster Layer

Return Value

LabelExplanationData Type
Output raster

The output raster that shows for each cell the upstream or downstream distance along a flow path.

Raster

Licensing information

  • Basic: Requires Spatial Analyst
  • Standard: Requires Spatial Analyst
  • Advanced: Requires Spatial Analyst

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