International Dredging Review

International Dredging Review

Medmerry Managed Realignment is the largest open-coast scheme in Europe the first in the United Kingdom and one of the most sustainable projects the United Kingdom Environment Agency has ever delivered. Located on the south coast of England in Sussex it was known to be one the most flood-prone and vulnerable parts of the southern coastline. The threat of flooding has long caused concern because of the risk to nearby towns as well as to the natural wetland and intertidal habitat.

The Medmerry Managed Realignment has been well recognized for its innovative approach. Most recently the project was honored in June at the World Dredging Association’s conference (WODCON) held in Miami Florida. The project team members were J T Mackley & Co Ltd. the United Kingdom Environment Agency The Royal Society for the Protection of Birds (RSPB) Arcadis and Jacobs who received the Environmental Excellence Award for Dredging for Coastal Restoration. 

Medmerry often faced problems caused by regular breaches of the shingle bank with the most recent flooding occurring in 2008 when more than £5 million (about US$6.6 million) of damage was caused. Annually the government had been spending some £300000 (about US$ 399000) to repair and maintain the shingle bank. The new flood bank is seven kilometers long (about 4.3 miles) parts of it are almost two kilometers (about 1.2 miles) inland from the open sea and it was built at a cost of £28 million (about US$37 million). 

According to the Institution of Civil Engineers London “Managed realignment is an environmental management approach that involves altering the location of the line of defense working to provide a more sustainable position from which to manage flood and erosion risks. It can involve advancement (moving for-ward) set back or breach of the existing defense line. Most commonly it involves establishing a new set back line of defense on the coast or within an estuary.”

Medmerry maximizes the creation of inter-tidal habitat replacing vital areas and allowing new defenses to be built protecting thousands more properties along the coastline. The UK EA and Van Oord successfully restored all assets before the fall of 2013 which demanded extensive planning and coordination of a number of experts working quickly and accurately.

The Medmerry project covers an area more 500 hectares (about 1236 acres) and used around 400000 cubic meters (about 523180 cubic yards) of clay was excavated from designated borrow pits to build the new flood banks. All material was sourced from within the site area which saved both time and thousands of truck deliveries of clay. The borrow pits increased the area of intertidal habitat. In addition one hundred percent of the excavated material was reused on the project. Ultimately the project protected 348 properties sewage works and one of the main roads in the area. It created 183 hectares (about 452 acres) of intertidal habitat realized a maintenance savings of £300000 ($US399000) per year and incorporated extensive public access and economic growth opportunities.

Another important aspect of the project was the establishment of a dedicated internal communications team made up of members from the Environment Agency The Royal Society for the Protection of Birds Van Oord and EC Harris with an official public liaison officer. This communication effort was essential to making clear to a broad range of stakeholders what was actually being accomplished. The real test came during the winter storms of 2013 to 2014 which were worse than those of 2008. No flooding occurred and no maintenance was required. Environmental monitoring of the Medmerry nature reserve will continue for five years after its completion.