A comparison in numerical solution of Richards equation

We consider the Richards equation for the fluid flow in variably saturated porous media, which is a crucial problem in several application fields like water resource management, assessment of water-related disaster and agriculture. So, efficient methods for the numerical solution of the Richards equation can provide great benefits for society. We define four numerical procedures for the solution of such an equation. The computational performances of these procedures are tested and compared in two experiments: a water infiltration problem for three types of soil, a landslide hazard evaluation on a geographical area