To retreat is to step back from the problem and avoid a potentially catastrophic blow. It is to move critical infrastructure and housing to safer ground and to allow the water into the city to alleviate flood risk. This is critically different from abandonment, as we propose a long-term planned and managed process.
Managed Retreat, or Managed Realignment is a method of removing or breaching coastal defences, allowing tidal seawater to flood areas previously protected. The line of defence is then relocated landwards. An advantage of this is to reduce the flood risk to vulnerable sites further inland and along the coast by moderating the tide and wave energy. However, the main driver is a reduction of ‘whole-life’ costs to the defence scheme and increased long-term sustainability. Much needed inter-tidal habitat is also created, such as salt-marsh and mud-flats.
In retreating, investment in existing structures and infrastructure is lost as the area is claimed or reclaimed by the sea. New investment must also be made in relocating communities and infrastructure out of harm’s way. However, money is saved by significantly decreased investment in flood defences.
To date, several pilot sites of managed realignment have been created and the monitoring process is showing promising results. However, these sites were previously free from human habitation. How do we retreat from a populated area, and one with a infrastructure critical to the nation? Is it possible and practical to retreat from such an area?