Intro


Managed realignment involves creating new intertidal zones along a coastal defensive structure, which provid
Managed Realignment.jpg
Managed Realignment Site
es new recreational areas, restores disappearing habitats, and increases the efficiency of coastal defenses. This type of coastal defense offers flood prevention and habitat sustainability, as opposed to traditional concrete defensive structures.


The intertidal zone is the area between the low and high tides. Over time, the intertidal zone becomes smaller, pressing against existing coastal defense structures. As the intertidal zone disappears, flood risks and the cost of further sea defenses increase. Managed realignment allows land between a new and old sea defense structure to act as the intertidal zone, which is more able to respond to coastal processes, and thus reduce the effects of coastal squeeze.[1]

Historical Background


Although managed realignment has been incorporated into coasts all over the globe, the UK has been the leader for many years in developing and implementing managed realignment strategies for their country. In the UK, the first deliberate managed realignment site was .8 hectares (approximately 2 acres), at Northey Island in the Blackwater Estuary, Essex, which was flooded in 1991.[2] Today, there are over fifty managed realignment sites located in the UK[3] along with sites in Germany, The Netherlands, France, Belgium, and the U.S.[4] Managed realignment began with the need for sustainable flood risk management. However, due to political pressure involving climate change (rising sea levels), and nature conservation, the focus for managed realignment has been shifted.[5] The Texas Open Beaches Act and the Coastal Wetlands Planning, Protection, and Restoration Act in Louisiana have been utilizing managed realignment for environmental conservation.

Applying "Soft" Coastal Defense


For political reasons, many nations are pursing engineering "soft" coastal defense, i.e. managed realignment, over "hard" coastal defense, such as concrete walls. Hard engineering has been used for centuries to protect against erosion and flooding. However, these structures led to the elimination of nearby natural habitats and recreational areas. Consequently, construction of new hard engineered structures have been banned or strictly regulated in many areas.[6]

Soft engineering incorporates natural defenses such as saltmarshes and mudflats, to provide flood prevention while sustaining natural habitats. Experimental managed realignment sites have been seen to improve and sustain natural communities while providing equal or greater flood protection as hard coastal defenses.

Successful Sites


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Orplands Realignment Site

In 1995, an experimental sustainable flood defense was constructed in Orplands, Essex, UK. The site incorporated saltmarshes and mudflats. By 2013, saltmarsh vegetation increased, aquatic life, such as eel, bass, and common goby were thriving, and bird usage of site had increased. No significant effect on hydrodynamic regime of River Blackwater was noted.[7]

In 2006 a compensatory habitat realignment site was constructed at Chowder Ness, located off the Humber river in the U.K. The site increase coastal protection while expanding slatmarsh and mudflat area, and recreating intertidal area which is used by various local species of birds. [8]

Further Research


Experimental sites are being constructed all over Europe and the U.S., and are monitored to observe impact on natural habitat and flood prevention. Nature conservation regulations have been driving managed realignment sites, but also enforce constraints. Regulatory agencies will need to continue to see the benefits of managed realignment before lifting preventative constraints. [9]

Managed Realignment Video




References


  1. ^ French, P.W. (2004). Managed realignment - The developing story of a comparatively new approach to soft engineering. Estuarine, Coastal and Shelf Science 67 409-423
  2. ^ Doody, J.P. (2004). ‘Coastal Squeeze’ – an historical perspective. Journal of Coastal Conservation, 10, 129- 138
  3. ^ HR Wallingford. 2013. "Estuarine and coastal managed realignment sites in England – how do model predictions compare with reality?". <http://www.hrwallingford.com/news/estuarine-and-coastal-managed-realignment-sites-in-england>. (December 2, 2015).
  4. ^ Esteves, L.S. (2014). Managed Realignment: A Viable Long-Term Coastal Management Strategy?. Springer. p. 20-22
  5. ^ Esteves, L.S. (2014). Managed Realignment: A Viable Long-Term Coastal Management Strategy?. Springer. p. 55,56
  6. ^ Esteves, L.S. (2014). Managed Realignment: A Viable Long-Term Coastal Management Strategy?. Springer. p. 4
  7. ^ HR Wallingford. 2013. "Estuarine and coastal managed realignment sites in England". <http://eprints.hrwallingford.co.uk/664/1/HRPP627-Managed_realignment.pdf>. (December 2, 2015). p.10
  8. ^ HR Wallingford. 2013. "Estuarine and coastal managed realignment sites in England". <http://eprints.hrwallingford.co.uk/664/1/HRPP627-Managed_realignment.pdf>. (December 2, 2015). p.18
  9. ^ DEFRA. (2008). DEFRA/ Environmental Agency Flood and Coastal Defence R&D Programme: Managed Realignment Review Project Report.