SAGA 9.4.2 | Tool Library Documentation

Topographic Wetness Index


Description

Calculates the Topographic Wetness Index (TWI) using the supplied rasters for slope (Beta), specific catchment area (SCA), and optional transmissivity (T) when the soil profile is saturated: TWI = ln(SCA / tan(Beta)) or with transmissivity TWI = ln(SCA / (T * tan(Beta)))


References


Parameters

 NameTypeIdentifierDescriptionConstraints
InputSlopegrid, inputSLOPE--
Catchment Areagrid, inputAREA--
Transmissivitygrid, input, optionalTRANS--
OutputTopographic Wetness Indexgrid, outputTWI--
OptionsGrid Systemgrid systemPARAMETERS_GRID_SYSTEM--
Area ConversionchoiceCONV-Available Choices: [0] no conversion (areas already given as specific catchment area) [1] 1 / cell size (pseudo specific catchment area) Default: 0
Method (TWI)choiceMETHOD-Available Choices: [0] Standard [1] TOPMODEL Default: 0

Command Line


Usage: saga_cmd ta_hydrology 20 [-SLOPE ] [-AREA ] [-TRANS ] [-TWI ] [-CONV ] [-METHOD ]
  -SLOPE: 	Slope
	grid, input
  -AREA:  	Catchment Area
	grid, input
  -TRANS: 	Transmissivity
	grid, input, optional
  -TWI:   	Topographic Wetness Index
	grid, output
  -CONV:  	Area Conversion
	choice
	Available Choices:
	[0] no conversion (areas already given as specific catchment area)
	[1] 1 / cell size (pseudo specific catchment area)
	Default: 0
  -METHOD:	Method (TWI)
	choice
	Available Choices:
	[0] Standard
	[1] TOPMODEL
	Default: 0