Gabions on par at St Andrews Jubilee Course

21/05/2001

Maccaferri was appointed main contractor to install sea defence revetments along the coast bordering the Eden estuary as part of a £200,000 investment aimed at saving the Jubilee Course, one of the championship golf courses which make up the world famous St Andrews Links Golf Complex. In a contract valued at £60,000, Gabions, Reno Mattresses, Bidim geotextile and bio-degradable erosion control materials were specified to arrest further erosion and stabilise the sand dunes along the shore line.

St Andrews is just one of several seaside golf links which are currently under threat of losing parts of the course to the sea. Damage caused by unusually strong westerly winds has caused the coastal dunes to retreat by several metres, resulting in significant amounts of sand being lost to the estuary and the North Sea. If left unchecked, these levels of erosion would seriously threaten the 8th fairway of the 105-year old Jubilee Course.

Course managers, the St Andrews Links Trust implemented plans to carry out major improvement work to arrest coastal erosion and prevent any further impact by the estuarine forces. The proposed solution was further complicated by the sensitive nature of the environment. The dunes are part of the overall estuary which is designated a Site of Special Scientific Interest (SSSI) and Fife Council required an environmental impact assessment to be undertaken before granting planning permission.

The approved scheme was designed by H R Wallingford, to include both ‘hard’ and ‘soft’ engineering solutions and the contract is being supervised by Fraser Smart Architects of Leven, Fife.

Commenting on the project, Fraser Smart said: "Once we had the approval of all concerned, it was vital to act quickly and prevent further damage to the links. The whole undefended face of the estuary is vulnerable to erosion, but our immediate task was to protect the most exposed areas, in particular the coastline adjacent to the Jubilee course, where the beach was less than 2 – 3 metres from the 8th fairway.”

The ‘hard’ engineering solution, comprising box Gabions and Reno mattress revetements, was employed in the most vulnerable areas, striking a balance between the differing priorities of organisations with an interest in the area. Maccaferri was awarded the contract following an open competitive tender and work commenced on-site in November 2000. The ‘soft’ engineering, covering the Gabion walls with 15,000 cubic metres of sand and recharging the beach, will be undertaken during 2001.

Commenting on the work completed by Maccaferri, Fraser Smart said: “With time of the essence, Maccaferri was able to utilise its specialist expertise to expedite the construction work, completing the coastal revetments within a very short time scale, helping to preserve the Jubilee links.”

A Gabion wall and Reno mattress revetment has been constructed along a 100-metre stretch of the most exposed coastal area. However, to preserve the natural shoreline, the Gabions are stepped to create a more natural sloping contour, with Reno mattresses used to stabilise the sand where the retaining properties of box gabions are not required. In addition to its aesthetic appeal, the rationale for this design is based on sound technical principles.

During stormy weather, breaking waves run up the Revetments and Reno mattresses, allowing the force of the water to be dispersed. In contrast, the forces of waves breaking against the vertical walls of box Gabions is refracted back into the estuary, further unsettling the already turbulent water.

Bidim F70, a high performance geotextile, has been laid underneath the Reno mattress revetment to provide a filtration system, allowing water to drain away while retaining the sand particles.

It is hoped that the combination of ‘hard’ and ‘soft’ engineering will be effective in preventing further erosion, the ‘soft’ solution buying additional time during which the various interest groups can consider the options open to them. Monitoring systems including a sophisticated GPS measurement system to record beach levels and profiles, wave strength and recordings of wind strength have been put in place. The movement of sand will be recorded to monitor the effectiveness of the combined ‘hard’ and ‘soft’ engineering solution.

Box Gabions are rectangular units fabricated from a double-twist, hexagonal mesh of PVC and Galfan coated steel wire. Galfan is a 5% aluminium/zinc mischmetal which provides enhanced corrosion protection characteristics when compared to conventional galvanising. The standard size for each gabion is 2m x 1m x 1m with a fixed diaphragm at 1m, but alternative sizes may be specified to meet precise specifications. Supplied folded flat, units are laced together using continuous 2.2mm diameter lacing wire or high tensile steel “C” rings attached using a special pneumatic assembly tool. Once assembled, each unit is filled with natural local stone to create a retaining structure which is in sympathy with the surrounding environment.

Reno mattresses are of similar construction but, as the name suggests, they are thinner in cross-section to afford the system maximum flexibility, a property which is essential for this type of structure.

The St Andrews contract also sees the first use of the Bidim F filtration range of products in the UK. A range of non-woven, needle-punched continuous fibre geotextiles developed specifically for filtration, Bidim F70 has been laid beneath the gabion revetments. Flexible, with very high resistance to working loads and excellent permeability, Bidim F allows surface water to drain away naturally while protecting and retaining the underlying soil.

The UK arm of the Maccaferri Industrial Group, headquartered in Italy, Maccaferri Ltd specialises in gabions, geotextiles, geogrids and geomats. In addition to a full range of products for retaining structures, slope reinforcement and erosion protection, the company offers an in-house construct, design and consultancy service.

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