Managed retreat or managed realignment is a coastal management strategy that allows the shoreline to move inland, instead of attempting to hold the line with structural engineering. At the same time, natural coastal habitat is enhanced seaward of a new line of defense. This approach is relatively new but is gaining traction among coastal policy makers and managers in the face of increased coastal hazard risks. There is a growing recognition that attempting to “hold the line” in many places is a losing battle.
In many cases of managed retreat, human development is “moved” out of harm’s way and natural areas are restored to enhance their ecosystem services. Typically, flood defenses are set back from the shoreline and flooding is allowed in the previously defended area. Usually, natural coastal habitat is preserved seaward of the man-made defense and it provides extra protection or a buffer from flooding.
Managed retreat can be complex and often contentious as it can include delineating a new line to which structures can be built and home and business owners must be bought out.
Components of managed retreat may include:
- Coastal planning
- Relocation and buy-back and Buy-Out programs
- Regulating types of development allowed
- Designating no-build areas
- Habitat restoration
- Replacement of built environment with green space
In this module, we will explore examples of managed retreat in the U.S. and the U.K. to gain an understanding of the complexities of implementing these projects. We will also consider the discussions of managed retreat options in large cities that are particularly vulnerable to inundation.
In addition, we will look at the dilemma of whole communities facing decisions to relocate in the face of repeated flooding as well as other mitigation measures such as elevating homes and changing building codes.