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..
| | Name | Type | Identifier | Description | Constraints |
|---|
| Input | Slope grid (rad) | grid, input | A | A slope angle grid (in rad__ans) | - |
| Catchment area grid (m2) | grid, input | B | A catchment area grid (in square meters) | - |
| Min Density grid (g/cm3) | grid, input, optional | Cmin | A grid representing minimum material density (in g/cm3) | - |
| Max Density grid (g/cm3) | grid, input, optional | Cmax | A grid representing maximum material density (in g/cm3) | - |
| Min Hydraulic conductivity grid (m/hr) | grid, input, optional | Dmin | A grid representing minimum material hydraulic conductivity (in m/hr) | - |
| Max Hydraulic conductivity grid (m/hr) | grid, input, optional | Dmax | A grid representing maximum material hydraulic conductivity (in m/hr) | - |
| Min Thickness grid (m) | grid, input, optional | Emin | A grid representing minimum material thickness (in m) | - |
| Max Thickness grid (m) | grid, input, optional | Emax | A grid representing maximum material thickness (in m) | - |
| Min Friction angle grid (degree) | grid, input, optional | Fmin | A grid representing minimum material friction angle (in degrees) | - |
| Max Friction angle grid (degree) | grid, input, optional | Fmax | A grid representing maximum material friction angle (in degrees) | - |
| Min Bulk cohesion grid (MPa) | grid, input, optional | Jmin | A grid representing minimum bulk cohesion | - |
| Max Bulk cohesion grid (MPa) | grid, input, optional | Jmax | A grid representing maximum bulk cohesion | - |
| Output | CR values | grid, output | G | Resulting critical recharge (m/day) grid | - |
| CR classes | grid, output, optional | H | Classified critical recharge (-) grid | - |
| Options | Grid System | grid system | PARAMETERS_GRID_SYSTEM | - | - |
| Global minimum density (g/cm3) | floating point number | fCmin | Constant value if no raster set | Default: 1.600000 |
| Global maximum density (g/cm3) | floating point number | fCmax | Constant value if no raster set | Default: 1.600000 |
| Global minimum conductivity (m/hr) | floating point number | fDmin | Constant value if no raster set | Default: 2.700000 |
| Global maximum conductivity (m/hr) | floating point number | fDmax | Constant value if no raster set | Default: 2.700000 |
| Global minimum thickness (m) | floating point number | fEmin | Constant value if no raster set | Default: 1.000000 |
| Global maximum thickness (m) | floating point number | fEmax | Constant value if no raster set | Default: 1.000000 |
| Global minimum friction angle (degree) | floating point number | fFmin | Constant value if no raster set | Default: 33.000000 |
| Global maximum friction angle (degree) | floating point number | fFmax | Constant value if no raster set | Default: 33.000000 |
| Global minimum bulk cohesion (MPa) | floating point number | fJmin | Constant value if no raster set | Default: 0.000000 |
| Global maximum bulk cohesion (MPa) | floating point number | fJmax | Constant value if no raster set | Default: 0.000000 |
| Parameter sampling runs | integer number | fK | Number of sampling cycles | Default: 1 |