Slope failures generally occur during or after prolonged periods of rainfall or an intense rainfall.
During rainfall, part of the rainwater will seep into the slope and fill up the voids among soil particles or rock fissures, leading to increase in groundwater pressure and decrease in ground strength and stability of the slope.
The ingress of precipitation can cause softening of the surface layers of cohesive soils, leading to reduction in effective cohesion of the soils and the development of shallow failure surfaces, i.e. debris flow.
Civil Engineer, Shimin Zhuang, discusses the special design considerations for slopes that are subject to heavy rainfall and climate change, taking a look at design methodology and good practices for slope protection.