Flood defences

At the launch of Future flood prevention, a report calling for changes to flood management in England to tackle the rising threat posed by climate change, Neil Parish, Conservative MP for Tiverton and Honiton, said, "Some five million people in England are at risk of flooding. Winter 2015-16 broke rainfall records. Storms Desmond, Eva and Frank disrupted communities across northern parts of the UK, with Desmond alone costing the UK more than £5 billion.

Flood defences are used to prevent or control the potential negative effects of flood waters. Traditional methods of flood defence, such as the planting of vegetation to retain water and constructing channels (floodways), have been used throughout history. More modern flood defences can include:

Dams.
Diversion canals.
Floodplains and groundwater replenishment.
River defences, e.g. levees, bunds, reservoirs, weirs, and so on.
Coastal defences, e.g. groynes, sea walls, revetments, gabions, and so on.
Retention ponds.
Moveable gates and barriers.

Temporary flood defences are systems that can be brought to specific problem sites to provide flood defence as required. They can then be removed until needed again, either at the same or a different location. They have no fixed foundation other than the ground on which they are based with perhaps minor pre-prepared modifications to ensure proper stability or performance of the equipment.

They might include:

Metal or plastic barriers.
Water or sand filled containers or bags.
Pumps.

Temporary barriers generally do provide the same level of protection as permanent defences and typically have failure rates of 20-30%, although this can be reduced by good advanced planning.

For more information see: Temporary flood defences.