Infiltration

Infiltration is the process by which water enters the soil. If the infiltration rate is greater than the precipitation intensity, all the water enters the soil profile and no overland flow occurs. Surface runoff or overland flow seldom occurs in non-perturbed forest soils because of the porus litter layer acting analogous to a sponge. Infiltration rates for surface layers of forest soils are generally in the range of 3 to 50 cm/hr, greatly exceeding most precipitation event intensities. Following timber harvest operations, loss of the litter layer and compaction of the surface horizons may result in decreased infiltration rates and surface runoff which induces soil erosion. Since the most fertile soil horizons occur at the surface of a soil, erosion of these horizons can result in a serious loss of the soil nutrient capital and reduction in stream water quality.