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Basin

Available with Spatial Analyst license.

Summary

Creates a raster delineating all drainage basins.

Usage

  • The drainage basins are delineated within the analysis window by identifying ridge lines between basins. The input flow direction raster is analyzed to find all sets of connected cells that belong to the same drainage basin. The drainage basins are created by locating the pour points at the edges of the analysis window (where water would pour out of the raster), as well as sinks, then identifying the contributing area above each pour point. This results in a raster of drainage basins.

  • To create the input D8 flow direction raster, the Flow Direction tool must be run using the default flow direction type D8.

    The best results will be obtained if when the input D8 Flow Direction raster was created, the Force all edge cells to flow outward option (FORCE in Python) was enabled.

  • All cells in the raster will belong to a basin, even if that basin is only one cell.

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

Syntax

Basin (in_flow_direction_raster)
ParameterExplanationData Type
in_flow_direction_raster

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

A flow direction raster can be created with the Flow Direction tool, using the default D8 flow direction type .

Raster Layer

Return Value

NameExplanationData Type
out_raster

The output raster that delineates the drainage basins.

This output is of integer type.

Raster

Code sample

Basin example 1 (Python window)

This example determines the drainage basins of an input flow direction Grid raster.

import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
outBasin = Basin("flowdir")
outBasin.save("C:/sapyexamples/output/outbasin01")
Basin example 2 (stand-alone script)

This example determines the drainage basins of an input flow direction Grid raster.

# Name: Basin_Ex_02.py
# Description: Creates a raster delineating all drainage basins.
# Requirements: Spatial Analyst Extension

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

# Set environment settings
env.workspace = "C:/sapyexamples/data"

# Set local variables
inFlowDirectionRaster = "flowdir"

# Execute FlowDirection
outBasin = Basin(inFlowDirectionRaster)

# Save the output 
outBasin.save("C:/sapyexamples/output/outbasin02")

Licensing information

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

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