Human Interaction With Rivers

Question 1

What effect does the three gorges dam have on the river

Answer 1

When people build dams or leaves it has several impacts of the operation of natural river processes

E.g the The three gorges dam

Building dams effects river transport processes

Building dams to control flooding interferes with the ability of the river to transport its load of sediment from source to sea

At the tree gorges dam in China a dam 185 meters high and 1.6 km wide was built across the river Yangtze - resivoir over 560 km long created behind it

The dam is used to generate power for major cities such as Shanghai and to prevent devastating floods which in the past killed hundreds of thousands

The floods have also been stopped

This has saved lives but farmland downstream from the dam is becoming infertile as it is starved of alluvium

Farmers now have to use expensive artificial fertilizers

Question 2

What effect do levees have ?

Answer 2

Building levees prevents the natural flood processes occurring

Levees are raised river banks deposited at the lower stage of a rivers course

These are natural river landforms but humans can also build levees and raise existing ones to prevent river flooding onto flood plain

Flood plains are flat fertile areas

Preventing rivers overflowing into their floodplains by interfering with natuaral flood processes has stoped damage to economically important developments such as factories and transport infrastructure

Because levees are so high the cannot flood naturally so it deposits its load on the river bed

Overtime the riverbed rises above the level of the flood plain and the levees are the only thing containing the river

This creates the need for stronger levees which are expensive to build and maintain

Levees cause river to flow faster due to narrower channels