Topographic Wetness Index (One Step)
| Author(s) | O.Conrad (c) 2014 |
| Library ID | ta_hydrology |
| Tool ID | twi |
| Version | 1.0 |
| Menu | Terrain Analysis | Hydrology | Topographic Indices |
Description
Calculates the Topographic Wetness Index (TWI) based on the supplied Digital Elevation Model (DEM). Slopes (Beta), Specific Catchment Areas (SCA), and a depressionless DEM for SCA calculation are derived internally.
TWI = ln(SCA / 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.
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
| | Name | Type | Identifier | Description | Constraints |
|---|
| Input | Elevation | grid, input | DEM | - | - |
| Output | Topographic Wetness Index | grid, output | TWI | - | - |
| Options | Grid System | grid system | GRID_SYSTEM | - | - |
| Preprocessing | choice | PREPROCESSING | - | Available Choices:
[0] Fill Sinks (Wang & Liu)
[1] Sink Removal
Default: 0 |
| Flow Routing | choice | FLOW_METHOD | - | Available Choices:
[0] Deterministic 8
[1] Rho 8
[2] Braunschweiger Reliefmodell
[3] Deterministic Infinity
[4] Multiple Flow Direction
[5] Multiple Triangular Flow Direction
[6] Multiple Maximum Downslope Gradient Based Flow Direction
Default: 0 |
Command Line
Usage: saga_cmd ta_hydrology twi [-DEM ] [-TWI ] [-PREPROCESSING ] [-FLOW_METHOD ]
-DEM: Elevation
grid, input
-TWI: Topographic Wetness Index
grid, output
-PREPROCESSING:
Preprocessing
choice
Available Choices:
[0] Fill Sinks (Wang & Liu)
[1] Sink Removal
Default: 0
-FLOW_METHOD:
Flow Routing
choice
Available Choices:
[0] Deterministic 8
[1] Rho 8
[2] Braunschweiger Reliefmodell
[3] Deterministic Infinity
[4] Multiple Flow Direction
[5] Multiple Triangular Flow Direction
[6] Multiple Maximum Downslope Gradient Based Flow Direction
Default: 0