Vegetation cover Vegetation can aid infiltration by slowing the flow of water over the surface and providing passageways along root systems for water to enter the soil. In desert regions or areas that have recently been deforested either by fires or humans, infiltration will be reduced, thus increasing the rate of runoff and decreasing the lag time. Different soil types have different capacities to absorb moisture. Soil type is to a large extent dependent on climate. For example a type of soil that forms in dry, desert-like environments has a thin layer of poorly developed soil overlying a crust of caliche.
Caliche is calcium carbonate that has precipitated out of water infiltrating though the thin soil.
The caliche zone acts as an impermeable layer though which water can only penetrate with difficulty. Such soils in deserts, combined with the lack of vegetation make flash flooding in desert areas more common. If the ground is frozen little water can penetrate. Thus rainfall after a period of cold temperatures may not be able to infiltrate through the frozen ground. Human construction Humans tend to pave the Earth with such things as parking lots, highways, sidewalks, and plazas that prevent infiltration of water into the soil.