People in coastal regions have always had to protect their coasts from the forces of the sea. Whether from the tides, from the surf, from recurring storms or from erosion caused by heavy rainfall events. In recent years, the effects of climate change have been added to this list: extreme weather and steadily rising sea levels increase these problems today and will do so in the future.
The vast coast of Africa has become an area of concern given that a large number of the population lives within 100km of the coast with valuable assets being located right on the coast. Furthermore, the economic influence of the coast and harbours around Africa, being at risk, is of high value and requires protection.
Engineers are aware of this problem and are pursuing various protection concepts. For example, rock armour is often used to protect damaged sections of beach from the sea. This is also the case in the UK at Beesands Beach, South Devon. Locally, Beesands is neighboured by Hallsands, the village infamously swept away by the sea in 1917, to the south and Slapton Sands, a barrier beach protecting a freshwater lagoon, to the north. The community at Beesands were under threat of losing their village green and several houses located inland due to coastal erosion and flooding.
Initially, rock armour was proposed as a solution for the majority of the area needing remediation. However, an alternative solution requiring less maintenance than rock armour and geotextiles was requested. As well as improving coastal erosion protection to the village green and inland properties, the objective of these works was to provide aesthetic improvements to the area.
Stones and stainless steel mesh resist the storms
These requirements led to the development of an innovative low-profile solution: High-tensile stainless steel mesh is quickly and efficiently constructed to form a ‘cell’ with fill material, bracing/tensioning components - all installed on site. The system is called TECCO CELL and offers minimal impact on the landscape yet gives maximum protection to the interface between the beach and its surroundings. TECCO CELL is a system designed to be modular, durable against coastal erosion that can withstand even extreme weather events.
Over time it has become evident that the system offers various benefits over conventional solutions:
- The mesh dissipates wave energy, preventing cut back erosion and erosion behind the defences. This is in sharp contrast to the splash action and erosion caused by wave impact on irregularly shaped rock armour/hard concrete walls/geotube.
- Maximum flexibility of the cell to move with changing beach levels, improving the anchoring ability of the cell over time.
- Minimum impact on environment during construction and when completed: No components that can be released into the environment, material can be recycled if cells are ever to be removed from site.
- Easily adapted to whichever coastal environment or morphology it is installed – i.e. planting or incorporating solutions for beach access to be maintained.
- Modular design allows for small areas as well as large stretches of coastline to be protected
- Resilience - monitoring of the performance of the existing solution installed at Beesands includes. testing on the corrosion of the material. Over a 4-year period there is absolutely no sign of corrosion on the stainless steel mesh material.
Economic advantages
A further 70 m of TECCO CELL solution has been installed in January 2021 at Beesands to protect the rest of the frontage of the village green and inland properties at a cost of £350,000. A costing exercise was undertaken to estimate the savings TECCO CELL solution provides over more traditional rock armour approach. It has been calculated that should a rock armour approach have been used on this section instead, the cost would be in excess of £525 000. In addition to this, rock armour has a maintenance cost which equates to approximately £10 000 per year. This is what has been spent at Beesands to recover rock armour that has moved due to the action of the sea since 2017.
Public Acceptance of TECCO CELL
This solution has been well received by the local community. There has not always been agreement regarding possible solutions for the coastal defences. However, locals state their preference for the TECCO CELL as a ‘sensible and extremely effective’ approach to the issues they are facing. Finally, they were very pleased with the extension of the TECCO CELL defences a further 70m along the northern frontage of the beach.
Weathering the Storms – The First Endurance Test
The first installations of these systems took place in 2016. These 1:1 field tests have proven the long-term durability of all elements. Following the storm “Darcy” which hit Beesands beach in early 2021 more information has been gathered from South Hams Council. Wave monitoring at Beesands showed that for over 24 hours the wave height exceeded the storm threshold, which was set at 3m. From 12.30 pm to 3 am the wave height was consistently even at over 7 m. Organisations such as the Environment Agency have given positive feedback on the TECCO CELL solution and are proposing installation at other key sites, with projects due to start this year.
Innovation by experts in their fields
In 2020, patents for TECCO CELL designs were filed by Shore Defence Ltd - a company comprised of team members who were instrumental in the design of this solution. The marine grade high-tensile stainless steel mesh is supplied by Geobrugg as the global leader in this technology. The solution ‘TECCO Cell’ is a product available for clients to purchase from Geobrugg, with consultation and support available for projects at each stage of the design and construction process. Currently the contractor Landmarc Environmental Engineering has carried out the installations at Beesands, these are also the designers of the TECCO CELL.
Since the original solution section was installed at Beesands, there have been considerable design improvements worked on by the designers and producers of the materials to improve buildability and resilience. This includes Geobrugg changes to their manufacturing machines to produce different sized mesh to enable improvements on the design and buildability.
Beesands and the section of the coast known as ‘Start Bay’ in South Devon have been a significant research area for teams at the University of Plymouth studying the effects of coastal erosion. They have monitored the installation of TECCO Cell since 2106 when the first section was constructed. The team has noted the reduction of erosion impact on the area behind the beach where TECCO CELL is installed compared with the sections of the beach that are not currently protected.
