River Management

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Diversion Channels

How it works:

Additional channels are built alongside the main river. These are connected to the min river channel through a series of sluice gates that can be opened during periods of prolonged rainfall.

Benefits:

The additional channels can take the excess water and prevent the water in the main channel from flowing over its banks.

Disadvantages:

Costly to construct and maintain.

Farmland may be compromised to make room for the new channels

Area around the main channel may be urbanised and offer no space for the additional channels

Dams and Reservoirs

How it works:

Huge walls are built across the rivers, usually in the upper course. An artificial lake is formed behind the dam.

Benefits:

Reservoirs store water during periods of prolonged rain. This reduces the risk of flooding. The water in the reservoir can be used for drinking, recreational activities and HEP

Disadvantages:

Dams are very expensive to build and settlements can be flooded when the reservoir is made.

Silt is deposited in the reservoir rather than on the floodplain resulting in farmland becoming less fertile

Channel Straightening

How it works:

Artificial channels are created in order to straighten the course of the river. Meanders may be cut off completely.

Benefits:

Water will travel out of the area more rapidly because it doesn't have meanders to negotiate. This helps reduce flood risk.

Disadvantages:

Flooding may occur downstream of the straightened channel as the water will reach this area faster.

There may also be more erosion downstream due to higher velocities.

'Do Nothing'

How it Works:

No money is spent on new flood defenses or on maintaining old ones.

Accept that flooding is a natural process.

People should accept the risks of living in an area likely to flood.

Benefits:

The river floods and eroded material is deposited on the floodplain making the farmland more fertile.

Disadvantages:

Neither the risk of flooding nor the impact of flooding are reduced.

A flood will probably occur and cause a lot of damage.

Flood Warnings

How it Works:

The Environment Agency warns people about possible floods through TV, radio and the Internet

Benefits:

The impact of flooding is reduced as warnings give people the time to move possessions upstairs, put sandbags in place and evacuate.

Disadvantages:

Warnings do not prevent floods.

Living in a vulnerable location may make it difficult to get insurance.

People may not receive the warnings in sufficient time.

Flood Plain Zoning

How it Works:

Restrictions prevent building on parts of the floodplain that are at risk of flooding.

Benefits:

The risk of flooding is reduced as less impermeable surfaces are created (e.g. buildings and roads).

The impact of flooding is reduced as less properties are located on the floodplain

Disadvantages:

The expansion of an urban area is limited if there are no other suitable construction sites.

It is no help in areas that have already been built on.

Preparation

How it Works:

Buildings are modified to reduce the amount of potential damage (e.g. stilts).

People make plans for what to do during a flood (e.g. emergency kit; important documents in a safe place)

Benefits:

The impact of a flood is reduced.

Buildings are less vulnerable and people are more prepared.

People are also less likely to worry about the threat of floods if they are prepared.

Disadvantages:

Preparation does not guarantee safety in a flood.

Could give people a false sense of security.

It's expensive to modify homes and businesses

Hard Engineering

Soft Engineering