Hard flood defences on the Mississippi
The dams in the Mississippi river are a hard flood defence. There are two different types of dams on the Mississippi River, wing dams and closing dams. Wing dams are built close together with brush and stone structures that extend from the river bank to the channel and closing dams are used to block connections between the main channel and side channels of the floodplains. The advantages of building dams on the Mississippi are that they enhance the electricity generating capacity for the surrounding regions and the river won’t dry up but just waits for more water to arrive. The disadvantage of building dams on the Mississippi is that it could cause flooding if there are too great amounts of water. The flow of major tributaries in places such as Missouri, Ohio and Tennessee has been controlled by a series of dams.
A Levee in the Mississippi river is a naturally occurring ridge or artificially constructed wall which regulates water levels and stops the river from flooding. They are parallel to the course of the river in its floodplain. Advantages of levees are that they can protect a building from the surrounding area of the Mississippi and there will be no pressure from the water to cause structural damage to the building. Disadvantages of levees on the Mississippi are that they may be expensive if they are artificially made and they require a lot of land area. Levees have been heightened in places to over 15 metres and strengthened and there are almost 3000km of levees along the main river and its tributaries.
Overspill channels on the Mississippi can store excess water in times of a flood and then release it after the risk of floods has past. Advantages of overspill channels are that they increase the capacity of the river by providing an alternative additional channel, especially during times of high flow and disadvantages are that there is a significant cost needed to form them and can lead to further problems...