As part of a series of measures to protect the freshwater habitats at Titchwell Marsh Nature Reserve on the north Norfolk coast, Salix has supplied the Royal Society for the Protection of Birds (RSPB) 2,000 metres of Rock Rolls.
Titchwell Marsh, which is owned and managed by the RSPB, is an internationally important site, with bitterns, marsh harriers and bearded tits breeding in the reedbeds; avocets and black-headed gulls breeding on the fresh marsh; and large populations of wading birds and wildfowl through the winter and migration periods.
The Marsh is under pressure from coastal processes so in 2009 work began to improve the area’s flood defences.
The sea defences were realigned over part of the reserve and the sea bank behind the brackish marsh – Parrinder Bank – was reinforced to protect the freshwater habitats.
The seawall to the west of the freshwater habitats was also strengthened and the old brackish marsh seawall was breached to allow it to revert to salt marsh.
“Thankfully, as a result of the coastal defence work undertaken between 2009 and 2011, the area’s catastrophic storm surge on 5 December 2013 did not breach Titchwell Marsh’s defences and the freshwater habitats survived intact.
However, a small amount of over-topping and some erosion of the base of one of the seawalls occurred. After consultation, it was decided to repair the damage and decrease the risk of further erosion by installing Rock Rolls along a 500-metre section of the base of the northern seawall.”
David Holland, Technical Director for Salix, says:
“Rock Rolls are a tubular revetment consisting of small granite stones retained within a high strength polyethylene net. They are capable of resisting high velocities and sheer stress in high energy water situations and can be used around reservoirs, lakes, streams and rivers, or along shorelines as at Titchwell Marshes.
As well as giving excellent erosion protection, they provide invertebrate habitat and accrete fine sediment, enabling vegetation to establish within the stones.”
Salix has designed its Rock Roll products in partnership with the European Soil & Water Engineering Group (ESWEG).