by Katie Edwards

Flooding - The Problem

A flood is when there is a large amount of water beyond its normal limits specially over what is normally dry ground surface. In other words, a flood is having too much water in the wrong place. Flooding is very dangerous, which can cause great damage to the environment, life and property, and has the potential to wipe away an entire city or area. Floods can come from a number of different sources such as a lot of rainfall and snow. Flooding also comes from high tides, storm surges and waves.

If flooding is not solved, people can become homeless, injured or killed, water supply and electricity will be interrupted, public transport like airplanes, buses, boats and trains will be delayed, and communication lines could be knocked down.

Dams - One Solution

One solution to flooding is building dams. Dams are huge walls that are built across rivers and streams to generate electricity, also making water available to agriculture and to control flooding.

A reservoir or a lake is formed behind the dam. Flood water is caught by the dam which prevents flooding downstream. The water is released steadily throughout the year.

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Advantages of Building a Dam

Dams gather drinking water for people. The steady water released throughout the year provides irrigation of land below the dam. The turbines that are often built into the dams help create clean energy and generate electricity. Dams keep areas from flooding and create lakes for people's recreational activities like swimming and sailing.

Disadvantages of Building a Dam

Dams can be very expensive. Land is flooded when a reservoir is created, which means farmland can be destroyed. People may be forced to leave homes and move elsewhere when their houses are flooded. Wildlife may be affected, fish migrating upstream to breeding grounds. Dams trap sediments that are carried in rivers. This can cause the dam to fail. It can also cause increased river erosion downstream as there is less sediment being deposited.

Affecting Society - Environmental Factor

The construction of large dams completely change the relationship of water and land destroying the existing ecosystem balance.

One of the first problems with dams is the erosion of land. Dams hold back the sediment load normally found in a river flow, depriving the downstream of this. In order to make up for the sediments the downstream water erodes its channels and banks. This lowering of the riverbed threatens the vegetation and river wildlife.

As fisheries become an increasingly important source and food supply, more attention is being paid to the harmful effects pf dams on many fish and marine mammal populations. The large majority of large dams do not include proper bypass systems of these animals, interfering with their lifecycle's and sometimes even forcing species to extinction.

Dam reservoirs in tropical areas, due to their slow-movement, are literally breeding grounds for mosquitoes, snails and flies, the vectors that carry dengue fever and malaria.