SAGA-GIS Module Library Documentation (v2.2.2)

Module SHALSTAB


This module is a realization of the SHALSTAB (Shallow Slope Stability) model from Montgomery & Dietrich (1994). The model computes grid cell critical shallow groundwater recharge values (CR in mm/day) as a measure for relative shallow slope stability, utilizing a simple model that combines a steady-state hydrologic model (a topographic wetness index) to predict groundwater pressures with an infinite slope stability model. For computation, a slope (in radians) and a catchment area (in m2) grid are required. Additionally, information on material density (g/cm3), material friction angle (°), material hydraulic conductivity (m/hr), bulk cohesion (MPa) and depth to potential shear plane (m) are required that can be specified either globally or through grids. The module produces a continuous CR (mm/day) raster with unconditionally stable cells blanked, and unconditionally unstable cells as CR = 0. Optionally, a classified CR grid can be calculated representing seven stability classes.

Reference: Montgomery D. R., Dietrich, W. E. (1994) A physically based model for the topographic control on shallow landsliding. Water Resources Research, 30, 1153-1171..

Parameters

 NameTypeIdentifierDescriptionConstraints
InputSlope grid (rad)Grid (input)A--
Catchment area grid (m2)Grid (input)BA catchment area grid (in square meters)-
Min Density grid (g/cm3) (*)Grid (optional input)CminA grid representing minimum material density (in g/cm3)-
Max Density grid (g/cm3) (*)Grid (optional input)CmaxA grid representing maximum material density (in g/cm3)-
Min Hydraulic conductivity grid (m/hr) (*)Grid (optional input)DminA grid representing minimum material hydraulic conductivity (in m/hr)-
Max Hydraulic conductivity grid (m/hr) (*)Grid (optional input)DmaxA grid representing maximum material hydraulic conductivity (in m/hr)-
Min Thickness grid (m) (*)Grid (optional input)EminA grid representing minimum material thickness (in m)-
Max Thickness grid (m) (*)Grid (optional input)EmaxA grid representing maximum material thickness (in m)-
Min Friction angle grid (degree) (*)Grid (optional input)FminA grid representing minimum material friction angle (in degrees)-
Max Friction angle grid (degree) (*)Grid (optional input)FmaxA grid representing maximum material friction angle (in degrees)-
Min Bulk cohesion grid (MPa) (*)Grid (optional input)JminA grid representing minimum bulk cohesion-
Max Bulk cohesion grid (MPa) (*)Grid (optional input)JmaxA grid representing maximum bulk cohesion-
OutputCR valuesGrid (output)GResulting critical recharge (m/day) grid-
CR classes (*)Grid (optional output)HClassified critical recharge (-) grid-
OptionsGlobal minimum density (g/cm3)Floating pointfCminConstant value if no raster setDefault: 1.600000
Global maximum density (g/cm3)Floating pointfCmaxConstant value if no raster setDefault: 1.600000
Global minimum conductivity (m/hr)Floating pointfDminConstant value if no raster setDefault: 2.700000
Global maximum conductivity (m/hr)Floating pointfDmaxConstant value if no raster setDefault: 2.700000
Global minimum thickness (m)Floating pointfEminConstant value if no raster setDefault: 1.000000
Global maximum thickness (m)Floating pointfEmaxConstant value if no raster setDefault: 1.000000
Global minimum friction angle (degree)Floating pointfFminConstant value if no raster setDefault: 33.000000
Global maximum friction angle (degree)Floating pointfFmaxConstant value if no raster setDefault: 33.000000
Global minimum bulk cohesion (MPa)Floating pointfJminConstant value if no raster setDefault: 0.000000
Global maximum bulk cohesion (MPa)Floating pointfJmaxConstant value if no raster setDefault: 0.000000
Parameter sampling runsIntegerfKNumber of sampling cyclesDefault: 1
(*) optional

Command-line

Usage: saga_cmd ta_slope_stability 2 [-A <str>] [-B <str>] [-Cmin <str>] [-Cmax <str>] [-Dmin <str>] [-Dmax <str>] [-Emin <str>] [-Emax <str>] [-Fmin <str>] [-Fmax <str>] [-Jmin <str>] [-Jmax <str>] [-fCmin <str>] [-fCmax <str>] [-fDmin <str>] [-fDmax <str>] [-fEmin <str>] [-fEmax <str>] [-fFmin <str>] [-fFmax <str>] [-fJmin <str>] [-fJmax <str>] [-fK <num>] [-G <str>] [-H <str>]
  -A:<str>    	Slope grid (rad)
	Grid (input)
  -B:<str>    	Catchment area grid (m2)
	Grid (input)
  -Cmin:<str> 	Min Density grid (g/cm3)
	Grid (optional input)
  -Cmax:<str> 	Max Density grid (g/cm3)
	Grid (optional input)
  -Dmin:<str> 	Min Hydraulic conductivity grid (m/hr) 
	Grid (optional input)
  -Dmax:<str> 	Max Hydraulic conductivity grid (m/hr) 
	Grid (optional input)
  -Emin:<str> 	Min Thickness grid (m)
	Grid (optional input)
  -Emax:<str> 	Max Thickness grid (m)
	Grid (optional input)
  -Fmin:<str> 	Min Friction angle grid (degree) 
	Grid (optional input)
  -Fmax:<str> 	Max Friction angle grid (degree) 
	Grid (optional input)
  -Jmin:<str> 	Min Bulk cohesion grid (MPa) 
	Grid (optional input)
  -Jmax:<str> 	Max Bulk cohesion grid (MPa) 
	Grid (optional input)
  -fCmin:<str>	Global minimum density (g/cm3)
	Floating point
	Default: 1.600000
  -fCmax:<str>	Global maximum density (g/cm3)
	Floating point
	Default: 1.600000
  -fDmin:<str>	Global minimum conductivity (m/hr)
	Floating point
	Default: 2.700000
  -fDmax:<str>	Global maximum conductivity (m/hr)
	Floating point
	Default: 2.700000
  -fEmin:<str>	Global minimum thickness (m)
	Floating point
	Default: 1.000000
  -fEmax:<str>	Global maximum thickness (m)
	Floating point
	Default: 1.000000
  -fFmin:<str>	Global minimum friction angle (degree)
	Floating point
	Default: 33.000000
  -fFmax:<str>	Global maximum friction angle (degree)
	Floating point
	Default: 33.000000
  -fJmin:<str>	Global minimum bulk cohesion (MPa)
	Floating point
	Default: 0.000000
  -fJmax:<str>	Global maximum bulk cohesion (MPa)
	Floating point
	Default: 0.000000
  -fK:<num>   	Parameter sampling runs
	Integer
	Default: 1
  -G:<str>    	CR values
	Grid (output)
  -H:<str>    	CR classes
	Grid (optional output)