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why are there no flood plains

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why are there no flood plains

LiL MiSs cHeEkY

why are there no flood plains in the upper course of a river valley?

Thanks fro any help in advance
xxx

Reply 1

Rogue275

Basically because the river is cutting down to reach sea level in its upper course and so won't flood until it has reached sea level and levelled out.
If the precipitation is heavy enough to cause floods the surplus water will just flow more heavily downhill. There may be occassional floods if the weather's bad enough, but not regularly enough to create flood plains as you would get further down the river.
In the lower course of the river gravity is not acting as heavily on the river as it has already reached sea level, therefore in heavy rain the river will flood outwards, rather than gravity just taking it downhill.

Apologies if that was poorly explained, hope it helps anyway.

Reply 2

LiL MiSs cHeEkY

thanks for your help, it wan't poorly explained at all! Thanks again :smile:

Reply 3

Armenian89

Upper course - vertical erosion
Middle course- lateral erosion
Lower course- flooding + lateral erosion (sinuousity increases -> meanders)

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