HUGE GEOSYNTHETIC bags filled with sand have been used to form the solid core of new sea defences for a golf course on the East Anglian coast.
Manufactured by Dutch firm TenCate Nicolon, Geotubes are made from Geolon woven geosynthetic. Already proven in the Netherlands, this is the first time the system has been used in the UK. It is designed to build embankments in inter-tidal zones to prevent material being washed away.
UK distributor Maccaferri supplied three 105m long, 3.25m diameter Geotubes for the scheme to build a 400m long sand embankment to protect the practice ground of the Royal North West Norfolk Golf Club at Brancester during spring tides.
The Environment Agency's original defence was a dune system with hard protection but this had become expensive to maintain and a policy of 'managed retreat' had been adopted. This, and demolition of banking to the west, would have left the practice ground unprotected.
Working with the EA, the golf club decided to build its own flood bank with private finance. North Norfolk consultant St La Haye was called in to design sea defences.
Because the golf club lies in a site of special scientific interest, local materials and construction methods were chosen to minimise environmental disturbance.
Local borrow pit material was unsuitable so it was suggested that sand from nearby tidal flats could be used. English Nature confirmed there was an area of little environmental value designated as 'barren sand'.
Principal contractor J Breheny Contractors excavated sand from the inter-tidal zone and transported it to a stockpile where it was mixed with water and pumped 500m to the bank site. Once the Geotubes were filled, local material was placed on top, profiled and covered with Enkamat erosion protection matting to create a smooth natural outline.
Two-thirds of the sand bank was built in just one week, considerably faster than other methods, said Maccaferri. The success of the project has meant that another Geotube may be used on an extension to the bank later this summer.