Sand containers stabilise slippery slope
Naue’s Secutex® Soft Rock sand containers have been installed at Hunmanby Sands, North Yorkshire, to reduce the significant coastal erosion which is threatening the sole access road to 45 residential properties at Flat Cliffs.
The hamlet of Flat Cliffs is situated within the terraces of an extensive undercliff landslide system above Hunmanby Sands; just south of Filey on the North Yorkshire Coast. The only vehicular access route into the hamlet is a road which runs through Primrose Valley Holiday Park and along the top of a coastal slope which is at significant risk from erosionand slope instability.
With Environment Agency funding in place, Scarborough Borough Council appointed Royal HaskoningDHV as Consulting Engineers to design and manage construction of the Filey Flat Cliffs Urgent Works Scheme and, since a key element of the scheme was to reduce the effect of waves eroding the toe of the cliff, the approved specification included the use of NAUE’s sand-filled containers.
With visible signs of movement in the slope it was essential that the project at Flat Cliffs was undertaken in a timely manner and, in March 2018, Scarborough Borough Council appointed its Term Maintenance Contractor, Transcore Ltd, to undertake drainage and slope stabilisation works.
Perfect low-cost solution for coastal erosion protection?
Naue’s Secutex® Soft Rock sand containers are the perfect low-cost solution for coastal erosion protection and, having had previous experience of working with the product, consultants Royal HaskoningDHV specified their use for the Flat Cliffs scheme.
Site access was somewhat restricted at Flat Cliffs, and only relatively small plant was allowed onto the beach. However, since Secutex® Soft Rock sand containers are delivered flat and ready for on-site filling, 200 containers which, when filled, would become 200 cubic metres of ballast with each container weighing up to 2 tonnes, were delivered to site on just two pallets. And, as Matthew Purvis, Civil Engineer with Royal HaskoningDHV explains: “Another reason we opted for the sand-filled bags was that they could be filled with locally won beach material, thus reducing transport costs.”
Fabricated from Secutex® needle-punched nonwoven geotextile, and utilising local fill materials, Secutex® Soft Rock sand containers provide an effective engineering solution in the construction of artificial reefs, groynes and breakwaters; providing erosion protection and stabilisation for beach nourishment measures. Secutex® RS 1201 has a proven record of long-term stability under saltwater and ultra violet conditions, and the open pore size of the fabric provides resistance to sand abrasion.
Another key advantage of the Secutex® Soft Rock construction is the product’s flexibility and adaptability; the option to vary the size and shape of Secutex® Soft Rock units offers major advantages over construction elements made from concrete, steel or rock, and the elongation capacity of Secutex® ensures that containers conform to uneven terrain with no loss of strength.
Secutex® Soft Rock sand containers provide drainage and erosion control in one durable product – transforming erosion-prone local material into an erosion-resistant system. The porous nature of the nonwoven geotextile allows sufficient ingress of water to dissipate wave energy, yet the sand fill is retained and the growth of vegetation is promoted; further enhancing the product’s erosion-limiting characteristics.
Installation is a simple process and, with site support from Naue, the installation team quickly mastered the methods for filling and closure of the containers. Transcore installed the 200 Secutex® Soft Rock sand containers along a 75 metre stretch at the cliff toe; significantly reducing the rate of erosion for years to come and reducing the risk of landslip adjacent to the residents’ sole access road.