This is a version of the Shalstab stability model for the evaluation of the proneness to instability of each pixel based on an infinite slope model with steady hydrological conditions.
The output is composed of two maps: the map of the potentially unstable pixels and the map of the minimum steady state rainfall to cause instability.
The parameters used for the evaluation of the stability conditions are:
- the contributing area draining across
- the contour length of the lower bound
- the soil transmissivity when saturated
- the local slope
- the ratio between soil bulk density and water density
- the net rainfall rate
- the gravitational acceleration
- the soil thickness
- the effective soil cohesion
For some of these parameters it is possible to insert as input either a map with the spatial distribution or a single constant value that will be used over all the basin (trasmissivity, tgphi, cohesion, hs, q, rho). There is the possibility to run a simulation where some parameters are maps and others are constant values.
The output is a map of values with the following meaning:
- 1 : unconditionally unstable
- 2 : unconditionally stable
- 3 : stable
- 4 : unstable
- 8888 : pixel characterized by rock (if soil thickness < 0.01)
It will be evaluated also the minimum rainfall to instability, and the output is a map of values with the following meaning:
- 0 : unconditionally stable
- 1 : 0 <= qcrit < 50
- 2 : 50 <= qcrit < 100
- 3 : 100 <= qcrit < 200
- 4 : qcrit >= 200
- 5 : unconditionally unstable
Inputs
- the map of slope
- the map of a/b
- a constant value or the map of trasmissivity
- a constant value or the map of the tangent of the friction angle
- a constant value or the map of cohesion
- a constant value or the map of soil thickness
- a constant value or the map of effective precipitations (net rainfall)
- a constant value or the map of the ratio between soil bulk density and water density
Output
- the map of the minimum rainfall to instability
- the map of stability classes