How does a managed retreat work?

Managed retreat is the controlled flooding of a low-lying coastal area and the creation of a wetland area, such as a salt marsh. If an area is at high risk of erosion, managed retreat could be an option. It usually occurs where the land is of low value, for example farmland.

Who pays managed retreat?

The federal government usually provides three quarters of the funding — via the Federal Emergency Management Agency or the Department of Housing and Urban Development — and state and local governments administer the programs and fund the balance.

What are the advantages of managed retreat?

Creates natural coastal habitat that provides protective functions. Initial costs are high but long term savings are likely. Provides a more sustainable long term solution. Returns land that floods regularly to natural habitat and reduces damage to property.

Why is managed retreat not done everywhere?

Managed retreat will not be the appropriate answer everywhere. Some places will build walls. Some will elevate. The reason the US needs managed retreat to be a viable adaptation option is that some places will retreat and some will need support to do so.

Is groynes hard or soft engineering?

Hard engineering – sea walls, groynes, rock armour They are generally placed at the foot of vulnerable cliffs or at the top of a beach. They can be up to 5m high and can be flat faced or curved. The curved walls are more expensive but dissipate the energy from incoming waves better.

Where is managed realignment used?

This section uses the creation of saltmarshes through managed realignment as an example because, to date, the managed realignment approach has only been applied in North-West Europe and North America, where saltmarshes are the dominant intertidal habitat.

What are the costs of sea walls?

A study by Linham et al. (2010) indicates that the unit cost of constructing 1 km of vertical seawall is in the range of US$0.4 to 27.5 million. The study found seawall costs for around ten countries.

What does managed realignment involve?

Managed realignment generally involves setting back the line of actively maintained defences to a new line, inland of the original or preferably, to rising ground. Doing so should promote the creation of intertidal habitat between the old and new defences, as shown in Figure 1.

What is a coastal squeeze?

Coastal squeeze is now defined as ‘the loss of natural habitats or deterioration of their quality arising from anthropogenic structures or actions, preventing the landward transgression of those habitats that would otherwise naturally occur in response to sea level rise in conjunction with other coastal processes.

What are gabions GCSE?

Gabions are large boulders piled up on the beach in steel cages. Absorb the energy of waves. Allows the build-up of a beach. They can be expensive to obtain and transport the boulders.

What is a gabion in geography?

Gabions are coastal defences that consist of rocks and boulders encased in a wired mesh. They absorb the energy from waves.