09 Rivers & Flooding

09 Rivers & Flooding - (I Rivers Flooding Rivers...

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(I) Rivers are bodies of surface flowing water confined within a channel Hydrologic cycle (refer to notes) Rivers as agents of erosion , deposition and transport ation 1. Downcutting Downward erosion of river into its bed The higher the velocity of river flow, the more rapid the erosion Dependent on the nature of riverbed material (For instance, solid rock is more resistant to erosion than is sediment) Processes: - Abrasion of waterborne sediments with the channel bottom and sides Chemical weathering of soluble rocks (e.g. limestone) Characteristically carves a narrow, steep-walled, V-shaped valley Meandering Combined effect of erosion and deposition from point to point along the length of river, causing a change in the channel geometry Meander cutoff leads to the formation of oxbows and oxbow lakes Floodplain A flat or gently sloping region around a river channel into which the river flows
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