Chapter 31 - Infiltration Rate, Surface Retention, Runoff.

Infiltration is the rate in which water soaks into the soil mass through the spaces between particles and openings in the soil. This infiltration rate depends on five factors: 1) the physical characteristics of the soil 2) the amount of moisture present in the soil 3) the type and extend of vegetation cover 4) the slope of the surface 5) the nature and duration of the rainfall. When a great amount of precipitation is introduced, such as in a rainstorm or during the spring as snow and ice melts, the water may exceed the infiltration rate. This means that the water is unable to infiltrate the soil, and remains on the surface of the soil in the form of puddles and pools. This surface water collects in irregularities in the soil surface, logs, twigs, and heaps of leaves, which act as micro-dams. This situation is called surface retention; when the water exceeds the ability of the micro-dams to retain it, the water flows over the land as surface runoff. This picture is form our fieldtrip to the Oxbow in the south of Edmonton.