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ENGEO <br /> INCORPORATED <br /> and/or organic debris which flow downslope with speed. Most of the material is transported <br /> away from the area of initial ground failure. <br /> Soil creep is the slow, often imperceptible, deformation of slope materials under low stress <br /> levels, which normally affects the shallow portion of the slopes, but can be deep seated where a <br /> weak zone of soil or bedrock exists. It results from gravitational and seepage forces, and may be <br /> indicative of conditions favorable for landsliding. Creep can be caused by wetting and drying of <br /> clays, by solution and crystallization of salts, by the growth of roots, by burrowing animals and <br /> by down slope movement of saturated ground. Colluvium refers to the mantle of loose soil and <br /> weathered bedrock debris that progresses down hillsides by creep. <br /> The District shall also be concerned with erosion and sedimentation affecting developed lots or <br /> improvements, subject to the provisions of Section II. Erosion is defined as the process by which <br /> earth materials are loosened and removed by running water on the ground surface or in the <br /> subsurface. Sedimentation is the depositing or settling of soil or rock particles from a state of <br /> suspension in a liquid. <br /> Hilly terrain open space either in a natural condition or particularly on excavated slopes can be <br /> subject to erosion. Landslide deposits which are sometimes in a loosened condition are <br /> particularly prone to erosion. Earth flow -, debris flow- and mud flow -type landslides typically <br /> have an area of deposition or accumulation (sedimentation area) at their base. Graded slopes in <br /> the District, particularly those in excess of 20 feet in vertical height or those not sufficiently <br /> vegetated, can be subject to erosion and therefore a source of transported sediment. <br /> 4867.1.002.01 <br /> October 10, 2000 6 <br />