Floodplain & Levees

Question 1

Floodplain

Answer 1

1- At times of floods the river overflows its banks.
2- The water loses energy as it goes over the vegetation and deposits sediment further away and large loads closer to the banks making a flat surface.
3- Hydraulic action and abrasion erode the outside banks whilst the loss of energy on the inside bank causes deposition, causing a level surface and lateral erosion. (at times of flood)
4- This is shown when meanders shift across the valley creating a wide flat area of land.

Question 2

levée- long narrow ridges or raised embankments alongside the river. (gravel stones etc)

Answer 2

1- When the river overflows the speed decreases and it deposits sediment.
2- The largest materail is deposited closer to the river,
3- After repeated floods , high banks called levées are formed at the sides of the river.
HOWEVER if the river floods with high levées then the water is less able to drain back into the river causing prolonged flooding problems.