From the arrival of the Romans to the Saxons and Normans clashing upon the shore, and from the Spanish Armada to Napolean and two World Wars, England has a long and well known history of coastal protection.
Today, coastal protection remains a high priority—though it now focuses on erosion and flood control and civil infrastructure. The West Sands Beach Project at Medmerry near Selsey and Sussex on the southeastern coast is the largest privately funded coastal protection scheme of its kind in the UK’s history.
MEDMERRY COASTAL PROTECTION
The Medmerry project is an extraordinary managed realignment scheme that is part of a wider program of integrated inland and coastal sea defenses.
More than 93,000t of rock have been shipped from Norway to create two breakwaters on a two-acre footprint, 600m apart, with 3,000m3 (nearly half a million tonnes) of sand and shingle deposited to form a beach.
Roughly 300 properties including numerous farms are located along the 650ha of low-lying land along this stretch of coast. A wastewater treatment plant and an electrical substation are also located inland and have been threatened by the area’s poor flood defenses. For many years, a raised shingle beach (more than 15,000t of shingle) has been used as defense, but flooding has caused significant damage, with the last flood season (2008-2009) causing more than £5m of damage between Selsey and Bracklesham.
This new, far more extensive approach is a major effort by the Environment Agency to establish real long-term protection for the coastline.
The project engineer (Atkins) specified NAUE Terrafix® B 813 to be used as the filter/separator geotextile between the Norwegian rock (which includes up to 10t boulders) and the sea bed.
The geotextile had to be robust enough to cope with such loading. It also had to be installed underwater during construction of the breakwaters.
Terrafix® B 813 is a unique geosynthetic. Two geotextiles encapsulate a sand layer. The increased density allows it to sink in water for easier installation and material control during such hydraulic engineering applications.
In “sinking” underwater, Terrafix® B 813 provided an efficiency that has made the installation process significantly quicker than that of a a conventional geotextile. This also resulted in welcomed project cost savings.
Full construction of the beach at Medmerry took place from April to September with an eight-week window for the geotextile installation. More than 24,300m² of Terrafix® B 813 were installed.
Learn more about coastal protection geosynthetics, exemplary projects, and other engineering solutions at www.naue.com.