Geography- Rivers

Levees are formed by the repeated flooding of a river which helps a levee form and the river must be carrying a large load. Also as a river floods it loses power, speed and velocity so it is able to drop sediments. The larger sediments are deposited closer to the channel and great thickness of alluvium can build up. Levees are also formed as the natural embankments at the side build up.

The effects of flooding would be:

• People being evacuated from there homes
• Houses destroyed
• Costly to repair the danage
• Trees are uprooted
• People die and are ill due to contaminated water

Flooding can be prevented by:

• Floodplaining zones
• Building Dams and resovoirs
• Building Levees
• Warning People
• Aforestation
• Straightening Meanders
• Preparation

There are many causes of flooding such as:

• Heavy rainfall
• Perlonged rainfall
• Snowmelt
• Dam Failure
• Steep Relief

A flood plain is flat ajacent land next to a river in the lower course. They do occur naturally but canbe increased in height by human interferace

Oxbow lakes occur when erosion causes the outside bend to get closer until there is only a bit of land left between the bends (this is called the neck.) The river break through this land usually during a flood and the river then flows through the shortest course depostion then eventually cuts of the meander forming an oxbow lake.

They are formed by Deposition, Erosion and bend gets more dramatia. Another feature is Thalweg.

Soft engineering is when you prevent floods naturally by waring people and aforestation this is good as it is cheap but doesnt always work.

Hard Engineering is when you use technology to prevent flooding such as building dams and reservoirs this prevents floods but is very expensive.

A flood plaining zone is where the flood risk across different parts of the floodplain is assesed and resulting in land use takes this into account. eg river then avoid the area very near river, pasture for grazing, playing fields, roads and car parks, industry, housing

It is formed when the soft rock gets eroded due to the splash back of water from the waterfall. A plunge pool is formed. The over of hard rock which sits above where the soft rock use to be collapses under gravity. The waterfall then retreats upstream to leave a gorge.