You experience the interplay between driving forces and resisting forces each time you drive down a steep slope. The main driving force in most land movements is gravity. The main resisting force is the material's shear strength. Slope angle , climate , slope material , and water contribute to the effect of gravity. Mass movement occurs much more frequently on steep slopes than on shallow slopes.
Water plays a key role in producing slope failure.
In the form of rivers and wave action, water erodes the base of slopes, removing support , which increases driving forces . Water can also increase the driving force by loading , i.e., adding to the total mass that is subjected to the force of gravity. An increase in water also contributes to driving forces that result in slope failure. The resistance to downslope movement is dependent on the shear strength of the slope material. Water contributes to resisting forces when sediment pores are partially filled with water.