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Rivers in past, present and future environments 06.12.18 (River types…
Rivers in past, present and future environments 06.12.18
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Slopes, hydrology and Rivers are interlinked
Intense rainfall events can trigger flood events, which can cause considerable erosion of steep slopes.
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Over large time scales (10's of 1000's of years|) this can can lead to the creation of river valleys
River types
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Constrained channels
As discharge increases, depth and the channel incises (downcutting channel leading to bed-level lowering)
Unconstrained channels
As discharge increases, depth increases to bank-full, then width increases rapidly.
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unvegetated bars- braided rivers- Multiple channels which divide and rejoin, unstable, migrating bands.
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There can be variations of river type within the one river e.g. Mekong River: Braided and Meandering.
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Rivers, climate change and future rivers
Changes in discharge- if it doesn't cross threshold to new channel type, then there is a change in size but not morphology.
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Future rivers
increased rainfall= increased run-off, the old discharge will be exceeded more often and max flow will increase.
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Rivers can change shape and morphology , often bursting through existing bank.
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May pose a huge flood risk. The indus river demonstrated flooding can occur through erosion rather than through too much water.
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