l5 levees & floodplain ap

3. Landforms resulting from deposition: Levees & Floodplains

3. Landforms resulting from deposition:

• Levees & Floodplains

Floodplain & Levees Formation

Floodplains and leveés are formed by deposition in times of river flood. The river’s load is composed of different sized particles. When a river floods it deposits the heaviest of these particles first as it does not have sufficient energy to carry them far away from the channel. The larger particles, often pebble-sized, form the leveés. The sands, silts and clays are similarly sorted with the sands being deposited next, then the silts and finally the lightest clays. Every time the river floods deposition builds up the floodplain.

Floodplain at Abergavenny

Levees

3. Landforms resulting from deposition: Levees & Floodplains

• _________ conditions – water contained in the channel

• Flood conditions – Water floods onto the ____ land adjacent to the river and ___________ material. _________ sediment is deposited first because the river lacks energy. Then lighter sediment is carried ________ across the flood plain as the ______ requires less _______ to move lighter sediment.

• Further Flat Heavier NormalDeposits Energy River