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

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.

Böhner, J., Selige, T. (2006): Spatial Prediction of Soil Attributes Using Terrain Analysis and Climate Regionalisation. In: Böhner, J., McCloy, K.R., Strobl, J.: SAGA - Analysis and Modelling Applications. Göttinger Geographische Abhandlungen, Vol.115, p.13-27. PDF

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. doi:10.1002/hyp.3360050103

Parameters

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