ArcGIS Tutorial: Water flow length

　　Summary

Calculates the upstream (or downstream) distance or weighted distance of the flow path along each cell.

　　Usage

· Water flow length The value type of the output raster is floating-point.

· The main purpose of the flow length tool is to calculate the length of the longest flow in a given basin. This measure is often used to calculate the aggregation time of a basin. This can be done using the upstream option.

The tool can also create a distance-area chart of hypothetical rainfall and runoff events by using the weighted raster as the impedance for downhill motion.

　　Grammar

Flowlength (In_flow_direction_raster, {direction_measurement}, {in_weight_raster})

　　Code instance

　　Flow Length (Flowlength) Example 1 (Python window)

This example calculates the downstream distance along the flow path for each cell.

Import arcpy

From arcpy Import env

From ARCPY.SA Import *

Env.workspace = "C:/sapyexamples/data"

Outflowlength = Flowlength ("Flowdir", "downstream", "" ")

Outflowlength.save ("C:/sapyexamples/output/outflowlen01")

　　Flow Length (Flowlength) Example 2 (stand-alone script)

This example calculates the downstream distance along the flow path for each cell.

# Name: _ex_02.py

# Description:

# 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"

Inweightraster = ""

Directiontype = "Downstream"

# Check out the ArcGIS Spatial Analyst extension License

arcpy. Checkoutextension ("Spatial")

# Execute

Outflowlength = Flowlength (Inflowdirectionraster, Directiontype, Inweightraster)

# Save the output

Outflowlength.save ("C:/sapyexamples/output/outflowlen02.tif")

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ArcGIS Tutorial: Water flow length