SAGA-GIS Module Library Documentation (v2.3.0)

Module Topographic Wetness Index (TWI)

Calculation of the slope and specific catchment area (SCA) based Topographic Wetness Index (TWI)

References:

Beven, K.J., Kirkby, M.J. (1979):
A physically-based variable contributing area model of basin hydrology'
Hydrology Science Bulletin 24(1), p.43-69

Boehner, J., Selige, T. (2006):
Spatial Prediction of Soil Attributes Using Terrain Analysis and Climate Regionalisation'
In: Boehner, J., McCloy, K.R., Strobl, J.: 'SAGA - Analysis and Modelling Applications', Goettinger Geographische Abhandlungen, Vol.115, p.13-27

Moore, I.D., Grayson, R.B., Ladson, A.R. (1991):
'Digital terrain modelling: a review of hydrogical, geomorphological, and biological applications'
Hydrological Processes, Vol.5, No.1

Parameters

 NameTypeIdentifierDescriptionConstraints
InputSlopeGrid (input)SLOPE--
Catchment AreaGrid (input)AREA--
Transmissivity (*)Grid (optional input)TRANS--
OutputTopographic Wetness IndexGrid (output)TWI--
OptionsGrid systemGrid systemPARAMETERS_GRID_SYSTEMGrid 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
(*) optional

Command-line

Usage: saga_cmd ta_hydrology 20 [-SLOPE <str>] [-AREA <str>] [-TRANS <str>] [-TWI <str>] [-CONV <str>] [-METHOD <str>]
  -SLOPE:<str> 	Slope
	Grid (input)
  -AREA:<str>  	Catchment Area
	Grid (input)
  -TRANS:<str> 	Transmissivity
	Grid (optional input)
  -TWI:<str>   	Topographic Wetness Index
	Grid (output)
  -CONV:<str>  	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:<str>	Method (TWI)
	Choice
	Available Choices:
	[0] Standard
	[1] TOPMODEL
	Default: 0