Sink function

Available with Spatial Analyst license.


Creates a raster layer identifying all sinks or areas of internal drainage.

For more information, see How Sink works in the Spatial Analyst tool help.

This is a global raster function.


A sink is a cell or set of spatially connected cells with a flow direction that cannot be assigned one of the eight valid values in a flow direction raster. This can occur when all neighboring cells are higher than the processing cell or when two cells flow into each other, creating a two-cell loop.

The Sink function only supports a D8 input flow direction raster layer. D8 flow directions can be created using the Flow Direction function and run with default flow direction type D8.

The output of the Sink function is an integer raster, with each sink being assigned a unique value. These unique values have a range that is between one and the total number of sinks. For example, if the total number of sinks were 1000, the unique values range from 1 to 1000.


Parameter nameDescription

Flow Direction Raster

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

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

Related topics

In this topic
  1. Overview
  2. Notes
  3. Parameters