Lecture8 soil erosion dung

VFU, 30-September-2014 Lecture #8 Soil erosion and Control of Erosion Principles of Watershed management Dr Bui Xuan Dung- Department of Environment Management What is Soil Surface Erosion? It is the movement of soil particles from one place to another under the influence of water or wind What are the types of soil erosion? • Water Erosion • Wind Erosion THE SOIL WATER EROSION PROCESS DETACHMENT Detachment Sediment Load Sediment Transport Soil DEPOSITION Sediment Load Deposition Soil Erosion     Erosion: displacement of soil particles; Soil loss or sediment production: mass transferred off of a hillslope or plot (“sediment production”); Usually divide by area, so units are: M L-2 T-1, where mass is in g, kg, or megagrams (Mg, or 106 g); Sometimes erosion is expressed as mass per unit of hillslope width (M L-1); Types of water erosion Water erosion Gully erosion Rill erosion Sheet erosion Splash erosion Greater potential for sediment movement Raindrop impact and splash Raindrop splash Rainsplash   Two processes involved in erosion:  Detachment; and  Transport; Rainsplash is the detachment and movement of particles resulting from the impact of a raindrop on the ground surface; Raindrop impact when there is a surface film of water; Rainsplash  Detachment and movement of soil particles due to raindrop impact: Kinetic energy = ½ m v2 m = mass of raindrop; v = velocity;    Drop size increases with rainfall intensity; Velocity increases with drop size until ~20 mm hr-1) (moderate intensity); Terminal velocity reached after ~10 m; Use thick-growing CROPS: Crops which cover the ground surface and fill the surface soil with fibrous roots tend to hold the soil in place and reduce erosion Cultivate On The Contour This is the practice of planting and cultivating of crops following the contours of the land Strip Cropping This is the practice of planting two crops in alternating strips or alternately planting a strip and leaving a strip fallow on land that would otherwise be erodible CONTOUR STRIP CROPPING Crawford Co Tillage Operation     Increase Infiltration Increase resistance for soil erosion Rough land surface against water and wind erosion Soil moisture retaining capacity No-Till (NT) Strip-Till (ST) Deep Till (DT) Mechanical practices 1.Terracing 2.Ponds and Dams 3.Vegetated Buffer Strip Terraces This is the practice of constructing embankment or ridges across sloping Ponds and Dams Artificial ponds hold or impound water which otherwise would be lost as runoff, and which in the process of runoff, would carry soil with it Vegetated Buffer Strip • A planted or natural vegetative buffer in the area that links to stream channel • SERVES AS: – Filter – Transform – Sink How Do Buffers Protect from erosion? Vegetation filters erosion in surface runoff Soil (also pollution) Source Flow resistance, High infiltration capacity ... THE SOIL WATER EROSION PROCESS DETACHMENT Detachment Sediment Load Sediment Transport Soil DEPOSITION Sediment Load Deposition Soil Erosion     Erosion: displacement of soil particles; Soil. ..What is Soil Surface Erosion? It is the movement of soil particles from one place to another under the influence of water or wind What are the types of soil erosion? • Water Erosion • Wind Erosion. .. or 106 g); Sometimes erosion is expressed as mass per unit of hillslope width (M L-1); Types of water erosion Water erosion Gully erosion Rill erosion Sheet erosion Splash erosion Greater potential