Final Review

Final Review - V. Erosional Processes Erosion Definitions...

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V. Erosional Processes Erosion Definitions Soil erosion—the process of dislodgement and transport of soil particles by wind and water Dislodgement—the initial movement of a soil particle from the place where it lay. Energy is required. Transport—the subsequent movement of a disloged soil particle. Energy is required. Geological erosion—erosion that takes place without human influence Tolerable soil loss—the maximum rate of soil erosion that will permit the indefinite maintence of soil productivity Surface erosion-- erosion that occurs on a land surface. Sheet erosion (Inter-rill)- erosion that occurs on a land surface from between concentrated flow paths. Rill erosion-- erosion that occurs on a land surface from within concentrated flow paths. Gully erosion-- erosion that occurs in well-defined channels. Mass movement (mass wasting)-- erosion that occurs as cohesive masses of displaced soil. Erodible- -a characteristic of soil or rock (passive). Erosive-- a characteristic of wind and water (active). Since one of the objectives of watershed management was to control or reduce accelerated erosion we shall now briefly consider the erosional process so that we may better understand what it is we are attempting to work with. There are two main categories of erosion: 1. Geological or natural 2. Man-induced Geologic erosion is a natural dynamic process resulting from the uplift of land masses and their subsequent reduction to base level. Man-induced erosion or accelerated erosion is that portion which exceeds the natural erosion phenomena. In our definition of erosion, we spoke of erosive agents and we shall study erosional processes from that standpoint. These agents are namely wind and water. Forms of Water Erosion: 1. Sheet Erosion 2. Internal Erosion 3. Channel Erosion 4. Mass Movement
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A. Water-- Forms of water erosion: 1. Sheet erosion- very common; extremely damaging; uniform removal of surface; often goes unnoticed at first. 2. Internal erosion- downward movement into the profile; plugs pores and lowers infiltration rates. Puddling- usually caused by rainfall action. 3. Channel erosion- o Rill- small channels which concentrate water. o Gully- deep into the subsoil. o Stream- from sides and bed of natural stream channel. 4. Mass movement-caused by lubricating action of water and pull of gravity. Erosion Classification for Watersheds (H.G. Wilm) Streams---- Class O: Stream shows no signs of erosion or excessive discharges. Banks well vegetated, often overgrown with woody vegetation. No recent debris or flotsam on banks or lodged in vegetation. Streambed formed of shingle or cobbles, weathered and often discolored by algae. Pools well-developed. Class I: Signs of incipient erosion. Banks undercut and raw in places; fresh sand and sediment in
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This note was uploaded on 11/14/2010 for the course NRM 4314 taught by Professor Fish during the Fall '10 term at Texas Tech.

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Final Review - V. Erosional Processes Erosion Definitions...

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