Landslide hazard and bioengineering: towards providing improved decision support through integrated numerical model development

The combined hydrology and stability model (CHASM) is a state-of-the-art software tool that aids the assessment of slope stability. The hydrological component of the model solves the Richard’s equation for saturated and unsaturated groundwater flow to derive the pressure head field as it changes through time. The generated hydrological conditions are used as input to limit equilibrium stability computations to derive factors of safety (FOS). The software can be applied to both site-specific problems as well as wide-area assessment to investigate the impacts of dynamic hydrology, with or without vegetation interactions, on slope stability. The program code, originally developed in a UNIX environment using Fortran ’77, has been implemented in the Microsoft Windows environment using C++ with the addition of a graphical user-interface (GUI) to enable more seamless and user-friendly operation. The GUI allows the user to initialise the slope geometry, define the hydrological, vegetation and geotechnical variables and, impose boundary conditions and initial conditions.