An interesting development in recent years is the understanding that slope stability analysis can be influenced by climatic events. Most geotechnical structures are not shielded from the influences of precipitation and evaporation. However, software tools have only recently been able to fully incorporate the potential influences of climate and its influence on the slope stability failures which may partially or fully go through the unsaturated zone. There are two key elements to analyzing this type of scenario:
Unsaturated shear strength - Any type of solution must be fully able to account for the increase in shear strength caused by an unsaturated soil.
Climatic coupling - Any solution must be able to handle the detailed climatic coupling on an atmospherically-exposed upper boundary. In other words, the relationship between precipitation, potential evaporation (PE), and actual evaporation (AE), must be able to be modeled. | 
