Tool 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.

Author: O.Conrad (c) 2003
Menu: Terrain Analysis|Hydrology|Topographic Indices

Parameters

	Name	Type	Identifier	Description	Constraints
Input	Slope	Grid (input)	`SLOPE`	-	-
	Catchment Area	Grid (input)	`AREA`	-	-
	Transmissivity (*)	Grid (optional input)	`TRANS`	-	-
Output	Topographic Wetness Index	Grid (output)	`TWI`	-	-
Options	Grid system	Grid system	`PARAMETERS_GRID_SYSTEM`	-	-
	Area Conversion	Choice	`CONV`	-	Available Choices: [0] no conversion (areas already given as specific catchment area) [1] 1 / cell size (pseudo specific catchment area) Default: 0
	Method (TWI)	Choice	`METHOD`	-	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