Final answer:
Water can increase slope susceptibility to failure through saturation, excess weight, and the development of debris and mud flows.
Step-by-step explanation:
Water can increase the susceptibility of a slope to failure in several ways. Firstly, when the slope material becomes saturated with water, it can lead to the development of debris flows or mud flows, which can block bridges, tributaries, and cause flooding. Secondly, excess weight from the accumulation of rain or snow can stress weak slopes and lead to failure. Lastly, water can weaken rock and soil slopes through saturation by snowmelt or heavy rains, making them more prone to failure.