Python code to implement some of the equations in Iverson (2000):
Iverson, R. M. (2000), Landslide triggering by rain infiltration, Water Resour. Res., 36(7), 1897–1910, doi:10.1029/2000WR900090.
Get the paper here: http://onlinelibrary.wiley.com/doi/10.1029/2000WR900090/full