Levees and Floodplains

Floodplain: the flat area next to the river channel, especially in the lower part of the course. This is a natural area for the water to spill onto when the river reaches the top of its banks. 

Levees: raised banks along the course of a river in its lower course. They are formed naturally but can be artificially increased in height. 

How are levees formed? 

• Rivers flood on a regular basis. The area over which they flood is known as the floodplain and this often coincides with regions where meanders form.
• When rivers flood in the middle valley the cover an area of land known as the flood plain.
• When they flood velocity is slowed and deposition of any rocks being transported is encouraged.
• This deposition leaves a layer of sediment across the whole floodplain.
• After several floods there are several layers of sediment (rocks) deep on the flood plain.
• In addition, the largest rocks and most deposition occurs next to the river channel.  This leaves a ridge of higher material next to the river channel on both banks of the river known as a levee.

Other information: 

• The largest material us deposited next to the channel as this is where the river starts to lose energy
• Smaller material is carried further away and then deposited