GENERAL GEOLOGY

Detailed explanation-1: -This mechanism of runoff generation is more common in drier climates where vegetation cover is sparse. In humid areas with greater vegetation cover, the water table may lie at the surface in low-lying areas or slope hollows, so that the soil there is saturated.

Detailed explanation-2: -During a heavy rainstorm, runoff is most likely to occur if the surface of the soil is (1) firmly packed clay-sized particles (2) loosely packed sand-sized particles (3) covered by trees, shrubs, and grasses (4) unsaturated and has a gentle slope.

Detailed explanation-3: -At the plot scale, vegetation helps reduce soil loss not only by reducing runoff volume, but also by changing the runoff-sediment yield relationship, resulting that the sediment-reduction rate is higher than the runoff-reduction rate. At the watershed scale, gully erosion and mass wasting process are dominant.

Detailed explanation-4: -Run-off is when water is forced by gravity to move across Earth’s surface towards larger water accumulations. Run-off that occurs on surfaces before reaching a channel, such as a river, is called surface run-off or overland flow.

Detailed explanation-5: -As a result of low infiltration and transmission rates, fine textured soils, such as clay, produce a higher runoff volume than do coarse textured soils, such as sand. Sites having clay soils may require the construction of more elaborate drainage systems than sites having sandy soils.