Factors Affecting Erosion by Water

The major variables affecting soil erosion are climate, soil, vegetation and topography. The climate factors and the topographic factors, except slope length, are beyond the power of man to control.

Now we discuss the factors as follows:

Climate:

Climate factors affecting erosion are precipitation, temperature, wind, humidity and solar radiation. Temperature and wind are most evident through their effects on evaporation and transpiration. However, wind also changes raindrop velocities and the angle of impact. Humidity and solar radiation are somewhat less directly involved in that they are associated with temperature. The relationship between precipitation characteristics, runoff and soil loss is complex. In a comprehensive study 19 independent variables, all measuring rainfall characteristics or interactions of combined characteristics, the most important single measure of the erosion-producing power of a rainstorm was the product, rainfall energy times maximum 30-min intensity; for runoff, it was rainfall energy for 24-hr antecedent precipitation.

Soil:

Physical properties of soil affect the infiltration capacity and the extent to which it can be dispersed and transported. These properties that influence erosion include soil structure, texture, organic matter, moisture content and density or compactness, as well as chemical and biological characteristics of soil.

Vegetation:

The major effects of vegetation in reducing erosion are interception of rainfall by absorbing the energy of the raindrops and thus reducing runoff, retardation of erosion by decreased surface velocity, physical restraint of soil movement, improvement of aggregation and porosity of the soil by roots and plant residue, increased biological activity in the soil and transpiration, which decrease soil moisture, resulting in increased storage capacity. These vegetative influences vary with the season, crops, degree of maturity, soil and climate as well as with the kind of vegetative material, namely, roots, plant tops and plant residues.

Topography:

Topographic features that influence erosion are degree of slope, length of slope, size and shape of the watershed. On steep slopes high velocities cause serious erosion by sediment transportation.

Beside these there is another factor which occur soil erosion and that is raindrop.

Raindrop Erosion:

Raindrop erosion is soil splash resulting from the impact of water drops directly on soil particles or on thin water surfaces. Although the impact on water in shallow streams may not splash soil, it does cause turbulence, providing a greater-sediment carrying capacity. Tremendous quantities of soil are splashed into the air, most of it more than once. The amount of soil splashed into the air as indicated by the splash losses from small elevated pans was found to be 50 to 90 times greater than the wash off losses.