A new revetment system based on high-strength steel-wire mesh filled with rock for coastal erosion control

Abstract

Recent years have seen a rise in both the intensity and frequency of storms, resulting in damage to coastal protection systems across the UK and globally. As a result, these systems have demanded substantial maintenance. For example, the gabion protection at Chesil Beach (Portland, UK) was severely damaged during the storms of February 2014, necessitating restoration costing at least £600 million. Similarly, the rock armor protection at Beesands (Devon, UK) also suffered damage in the same storm. These incidents highlight the urgent need to develop more resilient and innovative coastal defense systems. This fact gains further significance considering the UK's extensive coastal defense sector, necessitated by its vast coastlines with a length of approximately 30,000 km. According to various sources, approximately 18% of UK coastlines are protected with defense systems. Here, we introduce an innovative coastal defense system comprising high-strength steel-wire mesh filled with rock. The system is securely fastened using tension rod ensuring its long-term integrity and stability. The diamond mesh in this system features units measuring 8.3 cm in width and 14.3 cm in height. These units are filled with uniformly-sized rock units, typically ranging in diameter from 15 cm to 25 cm. The high-tensile stainless-steel mesh, referred to as 'Tecco Cell’, is supplied by Geobrugg Inc. Therefore, we name this system as Tecco Cell (TC) revetment hereafter. The TC revetment carries the advantages of both gabion and rock revetments and minimizes their drawbacks. Gabion baskets or mattresses are susceptible to a significant weakness: their wire baskets can be damaged or broken by the force of strong waves. For rock armor, the rock units are displaced by strong waves resulting in the collapse of the defense system. The TC revetment systems alleviate both drawbacks; their high-strength mesh resists waves, while the tension rods, combined with the mesh, stabilize the system even against the strongest waves. The TC revetment was installed along a 120-meter stretch of the coast in Beesands (Devon, UK) in 2016. Over the past seven years, it has effectively defended the coast with minimal maintenance needs. Despite encountering several winter storms since its installation in 2016, the TC system in Beesands has remained resilient. The purpose of this research is to report the results of two phases of laboratory tests on a 1/10 scaled model of a TC revetment. In Phase 1, eight tests were delivered on three types of revetments: gabion (two tests), rock armor (two tests) and TC revetments (four tests). In Phase 2, we conducted 32 tests comparing TC (16 tests) and rock armor (16 tests) revetments. It was found that the TC revetment consistently outperformed rock armor in terms of run up control and wave oscillations with an average runup reduction of 15%. We developed empirical equations for wave runup. Thanks to the successful implementation of the TC revetment in Beesnads (UK), there is now consideration for applying this new coastal defense system in Ritoque (Chile) and along the northwestern coast of Italy.