human impact on river processes Flashcards
what happens when people build dams and levees rot control river flooding
it has several impacts on the operation of natural river processes e.g. three gorges dam in china
what is the three gorges dam in china
185 metres high and 1.6 kilometres wide and was built across the river yangtze
what was created behind this dam
a reservoir over 560 kilometres long
what is this dam used for
generate power for major cities such as Shanghaiwha
what else is this dam used for
tp prevent devastating floods which in the past have killed hundreds of thorusdansd of people
what has damming the river prevented
the transport of fertile alluvium downstream
what has this done
saved lives but farmland downstream from the dam is becoming infertile as it is starved of the life giving alluvium which would have been deposited by the floods
what do farmers now have
use expensive artificial fertilisers on their land
what has buying levees prevented
natural flood processe from occurring e,g, along the river rhine in Germany
what are levees
raised river banks deposited in the lower stage of a rivers course
what are these
natural river landforms but human also built levees to raise existing levees to stop a river flooding onto its floodplain
what are flood plains
falt, fertile areas
what happens because the levees are so high
the river cannot flood naturally - so it deposits its load on the riverbed
what occurs oveime
raises the riverbed above the level of the flood plain and so the levees are the only thing containing the river
what does this create
a need for higher stronger levees
