GEOG 1290 Lecture Notes - Lecture 17: Bed Load, Aggradation, Broad Valley
14 Nov 2017
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Document Summary
Originally, streams begin as a succession of lakes, falls and rapids. Eventually the stream erodes to create a graded profile - graded stream. Begins as streams are established on initial landforms. Falls cut back and rapids are trenched out -draining lakes and ponds. Stream capacity is > the load supplied little to no alluvium accumulates. Abrasion results in deepening of major channels forming gorges or canyons. Weathering and mass wasting along canyon walls contribute to stream sediment load. Overland flow creates new branches also contributing to sediment load. Slope is decreased to a graded profile by rapids causing slower flow, resulting in greater deposition and lower erosion and an even more graded profile. Eventually supply of load from upstream matches the stream"s capacity. At this point the stream begins to meander developing arcs and curving bends, cutting into the stream channel walls causing the river to widen. At the same time alluvium accumulates on the inside of bends.
