Tool SHALSTAB

This tool 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 tool 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..

Author: A. Günther (c) 2012
Menu: Terrain Analysis|Slope Stability

Parameters

	Name	Type	Identifier	Description	Constraints
Input	Slope grid (rad)	Grid (input)	`A`	-	-
	Catchment area grid (m2)	Grid (input)	`B`	A catchment area grid (in square meters)	-
	Min Density grid (g/cm3) (*)	Grid (optional input)	`Cmin`	A grid representing minimum material density (in g/cm3)	-
	Max Density grid (g/cm3) (*)	Grid (optional input)	`Cmax`	A grid representing maximum material density (in g/cm3)	-
	Min Hydraulic conductivity grid (m/hr) (*)	Grid (optional input)	`Dmin`	A grid representing minimum material hydraulic conductivity (in m/hr)	-
	Max Hydraulic conductivity grid (m/hr) (*)	Grid (optional input)	`Dmax`	A grid representing maximum material hydraulic conductivity (in m/hr)	-
	Min Thickness grid (m) (*)	Grid (optional input)	`Emin`	A grid representing minimum material thickness (in m)	-
	Max Thickness grid (m) (*)	Grid (optional input)	`Emax`	A grid representing maximum material thickness (in m)	-
	Min Friction angle grid (degree) (*)	Grid (optional input)	`Fmin`	A grid representing minimum material friction angle (in degrees)	-
	Max Friction angle grid (degree) (*)	Grid (optional input)	`Fmax`	A grid representing maximum material friction angle (in degrees)	-
	Min Bulk cohesion grid (MPa) (*)	Grid (optional input)	`Jmin`	A grid representing minimum bulk cohesion	-
	Max Bulk cohesion grid (MPa) (*)	Grid (optional input)	`Jmax`	A grid representing maximum bulk cohesion	-
Output	CR values	Grid (output)	`G`	Resulting critical recharge (m/day) grid	-
Output	CR classes (*)	Grid (optional output)	`H`	Classified critical recharge (-) grid	-
Options	Grid system	Grid system	`PARAMETERS_GRID_SYSTEM`	-	-
	Global minimum density (g/cm3)	Floating point	`fCmin`	Constant value if no raster set	Default: 1.600000
	Global maximum density (g/cm3)	Floating point	`fCmax`	Constant value if no raster set	Default: 1.600000
	Global minimum conductivity (m/hr)	Floating point	`fDmin`	Constant value if no raster set	Default: 2.700000
	Global maximum conductivity (m/hr)	Floating point	`fDmax`	Constant value if no raster set	Default: 2.700000
	Global minimum thickness (m)	Floating point	`fEmin`	Constant value if no raster set	Default: 1.000000
	Global maximum thickness (m)	Floating point	`fEmax`	Constant value if no raster set	Default: 1.000000
	Global minimum friction angle (degree)	Floating point	`fFmin`	Constant value if no raster set	Default: 33.000000
	Global maximum friction angle (degree)	Floating point	`fFmax`	Constant value if no raster set	Default: 33.000000
	Global minimum bulk cohesion (MPa)	Floating point	`fJmin`	Constant value if no raster set	Default: 0.000000
	Global maximum bulk cohesion (MPa)	Floating point	`fJmax`	Constant value if no raster set	Default: 0.000000
	Parameter sampling runs	Integer	`fK`	Number of sampling cycles	Default: 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 <double>] [-fCmax <double>] [-fDmin <double>] [-fDmax <double>] [-fEmin <double>] [-fEmax <double>] [-fFmin <double>] [-fFmax <double>] [-fJmin <double>] [-fJmax <double>] [-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:<double>	Global minimum density (g/cm3)
	Floating point
	Default: 1.600000
  -fCmax:<double>	Global maximum density (g/cm3)
	Floating point
	Default: 1.600000
  -fDmin:<double>	Global minimum conductivity (m/hr)
	Floating point
	Default: 2.700000
  -fDmax:<double>	Global maximum conductivity (m/hr)
	Floating point
	Default: 2.700000
  -fEmin:<double>	Global minimum thickness (m)
	Floating point
	Default: 1.000000
  -fEmax:<double>	Global maximum thickness (m)
	Floating point
	Default: 1.000000
  -fFmin:<double>	Global minimum friction angle (degree)
	Floating point
	Default: 33.000000
  -fFmax:<double>	Global maximum friction angle (degree)
	Floating point
	Default: 33.000000
  -fJmin:<double>	Global minimum bulk cohesion (MPa)
	Floating point
	Default: 0.000000
  -fJmax:<double>	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)