GEOL 118 Lecture Notes - Lecture 34: Coastal Erosion, Landform, Drainage Divide
30 Apr 2016
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Geol 118 - lecture 34 - river principles ii. Dam construction traps all sediment in reservoir, resulting in upstream deposition and downstream erosion, including coastal erosion. Water discharged downstream of dam increases downstream erosion. In cross-section, valleys shaped like letter v, channel occupies nearly all of valley bottom. In map view, channel follows ~straight paths because water seeking shortest distance down steep slope. Typical gradient of mountain river = 10-40 m/km. Broad, flat area consisting of sediment deposited during flood. Typical rivers in plains, near river mouth. Natural levees (low, wedge shaped lenses of sediment along river channel) commonly form due to deposition during flooding (river slows due to friction as it overflows channel) Constantly changing course due to continuous erosion and deposition along meanders. When river changes direction, zone of maximum velocity shifts from middle to outer part, causing erosion there. Inner part of meander has reduced velocity, causing deposition of sand and gravel there.
