River Flooding and Management

Flooding

Floods can bring both advantages and disadvantages to an area. Floods can deposit rich, fertile alluvium in agricultural areas. Also, flood water can replenish irrigation channels. On the other hand, floods can destroy food supplies, homes and transport infrastructures.

Causes of flooding

Human causes:
Deforestation – Cutting down trees causes increased run-off (water flowing over the surface of the earth). Rainwater reaches rivers faster. Flooding becomes more likely.

Urbanisation – Man-made surfaces such as concrete result in a greater run-off. Rainwater reaches rivers faster and can cause flooding.

Natural causes:

• Heavy rainfall
• Melting snow

Effects of flooding

Flooding can have a significant impact on people. These are known as social impacts. Social impacts can include:

• damage to property
• injury or loss of life

Flooding can also have an impact on wealth. This is known as an economic impact. Economic impacts of flooding include:

• cost of repairs
• reduced tourism

Finally, flooding can have an impact on the surrounding landscape. Environmental impacts of flooding can include:

• loss of livestock
• loss of habitat
• destruction of crops

Managing Flooding – Hard Engineering

Dams
Although very expensive, dams can significantly reduce the risk of flooding downstream

Levees
These are man-made embankments constructed along the edge of the river. They increase the capacity of the channel to prevent the overflow of water.

The video below shows a levee constructed at Cockermouth, Cumbria following the 2009 floods.

Flood Defence Barriers
Similar to levees, only constructed from man-made materials flood defence barriers increase the channel size of a river which prevents the overflow of water.

The video below shows flood defence barriers at Cockermouth, constructed after the 2009 floods.

Managing Flooding – Soft Engineering

Afforestation
Planting more trees reduces run-off and increases interception.

Flood Plain Zoning
Floodplain zoning policies influence how land on, or close to, floodplains are used.

River restoration involves removing any hard-engineering strategies and restoring the river to its original course. This can involve making the river less straight which can slow the flow of the river.