Levee Formation Flashcards
levee definition
A levee is a wide ridge of sediment on the banks of a river. They are landforms of deposition often found in the lower stage of sediment-laden rivers
levee example
River Moy in Co Mayo
river deposition definition
River deposition occurs when the river loses energy and cannot carry its load. This can happen for a variety of reasons, for example the river may slow down when it floods onto its floodplain and suddenly becomes shallower
flooding’s impact
Levees form due to flooding. During normal flow the river is confined in its channel and deposition will occur on the riverbed. However, during flood events the river overflows its channel and pours over the floodplain
after flooding
Once a river has overflowed its channel, it will slow down due to the sudden decrease in depth and the fact that it has escaped its channel and now had a wider area to flow over
because of overflowing
There is a loss of energy that causes deposition. The heaviest stones are deposited first, closest to the banks, while the finer alluvium is carried further away across the floodplain
repeated flooding
Over repeated flooding, the deposits of heavy sentiment build up on the banks and form ridges called levees
natural protection
Levees are the river’s natural defence against flooding. They keep the river within its channel as every time the river floods it will have to rise higher to escape over the levees
eventually..
Eventually, deposition on the riverbed combined with natural levee-building leads to a situation where the bed of the river channel is above the level of the floodplain and the levees are the only thing preventing it flowing over the floodplain
human interference
When humans reinforce levees or build artificial ones, it can interfere with the river’s natural flood processes and trigger more extreme floods further downstream. This can be seen along the rivers Rhine and Mississippi
