PLAN341 Lecture Notes - Lecture 12: Rill, Sediment Transport, Flow Velocity
20 Mar 2016
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Document Summary
Sedimentation is a problem for rivers because it affects: productivity, geomorphic aspects, water quality, ecology of the system. Takes into account losses from sedimentation in rivers including loss of crop productivity due to degraded soil: during past 12000 years annual sediment loss worldwide has increased form 9 to 20 billion tons. Types of soil erosion by water: raindrop erosion. Raindrop hitting a particle and moving downslopesize (1 to 7 mm) Raindrops dislodge soil particles that move 1 to 2 m. After soil saturates and water flows down hill. Detachment of soil particles by raindrop impact and their removal downslope by water flowing overland as a sheet instead of in definite channels or rills. More or less uniform layer of fine particles is removed from the entire surface of an area, sometimes resulting in an extensive loss of rich topsoil. If precipitation is higher than the infiltration rate it will runoff: rill and gully erosion.
