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Building with Nature Guideline > Building Solutions > Shoreline zonation strategies > Managed realignment 

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Managed realignment

 

Controlled inundation of land by setting back the sea defence is an increasingly used method for coastal protection that anticipates to climate change. In the United Kingdom this so-called “managed realignment” is applied widely and considered a cost-effective and sustainable response to loss of salt marsh habitat and sea level rise. It is also applied in other countries such as the United States, Germany and Belgium.

 

By re-inundating land the coastline is placed backwards and a new intertidal area is created. The area is enclosed by a new dike on the landside to ensure safety of the hinterland. The goal is to create the right circumstances for succession of salt marsh vegetation. Once salt marshes develop, the vegetation will enhance sedimentation, the area will increase in elevation and will thus be able to grow with sea level rise. Furthermore, salt marshes can reduce wave energy and improve the stability of the dike.

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How to Use

Once the dike is breached and the managed realigned area is subject to tidal influence, the area will start to develop. Development of salt marshes is crucial for two reasons. First, once salt marshes develop, large scale erosion is unlikely to occur. Salt marsh vegetation will enhance sedimentation and creation of the area that will reduce waves and improve safety. The second reason is that managed realignment is often used as nature development and compensation measure. This is aimed at creation of salt marshes because they are a valuable habitat that can support biodiversity and ecosystem services. The practice of managed realignment should therefore by aimed at the development of salt marsh vegetation. Several boundary conditions need to be met in order to be successful.

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Practical Applications

Design can greatly differ amongst managed realignment sites, depending on goals (coastal protection, nature development, retention) and specific local conditions. Pontee (2007) distinguishes three main categories:

  1. banked realignment
  2. breached realignment
  3. regulated tidal exchange

Two other related applications are described in separate Building Solutions:

  1. Coastal buffer zones, or "inlaag", as traditionally used in the Southwest Delta of the Netherlands
  2. Inland shores, recently applied along the coast of Lake IJsselmeer in the Netherlands.

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References

 

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