2. Erosion Processes

Recognition of the type of erosion occurring on an area and knowledge of factors controlling erosion are important in avoiding problem areas and in designing control measures. Erosion can be broadly classified into two types -mass erosion and surface erosion. Mass erosion includes all erosion where particles tend to move en masse primarily under the influence of gravity forces, It generally includes various types of landslides plus nonrainfall associated erosion (dry creep). Surface erosion is defined as movement of individual soil particles by forces other than gravity alone such as overland flow of water and raindrop impact. Here, dry creep will be considered a surface erosion process because many soil stabilization measures designed to control surface erosion are also effective in controlling dry creep.

Surface erosion ia a function of three factors: (a) the magnitude of forces available (wind, raindrop splash, overland flow, and so forth); (b) the inherent erosion hazard at the site in question (soil detachability characteristics, slope gradient, and so forth); and (c) the amount of material available to protect the soil surface (vegetation, litter, mulches, and so forth). Mass erosion is controlled by the balance between the shear strength and the shear stress within the soil or fill material at the site in question; as long as shear strength exceeds shear stress, the site remains stable.

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Last Modified: 07/05/2007