Presence of Vegetation | Permeability of Rocks | Size of Drainage Basin | Climate |

The permeability of rocks is determined by the size of the pores between the rock particles. If the rock has small pores, water cannot easily infiltrate into the rock and this means that the rock is impermeable. On the other hand, if the rock has large pores, water can easily infiltrate and thus the rock is permeable. When water flows through an area of impermeable rock,little water infiltrates the ground, as a result there is high surface runoff and leads to a high volume of flow of water.