Physical modelling of steel-mesh rock revetments (mattress gabions) for coastal defence

As the rate of coastal erosion continues to increase worldwide, exacerbated by sea level rise, so too does the need for sustainable and effective coastal defence solutions. One relatively novel option is the steel-mesh cobble/rock revetment. The typology’s mesh allows for a monolithic continuity of filling material without the high embodied carbon, construction costs and large thickness that alternative revetments require. There exists a gap in physical testing of varied wave conditions meaning that: although proven in riverine environments, the use of steel-mesh cobble/rock revetments in coastal conditions has been sparse.   With aim to further understanding of this coastal defence typology, this paper presents a 1:10 scale physical experiment under varied periodic and nonperiodic (solitary) wave conditions. Through quantitative and qualitative analysis, the steel-mesh cobble/rock revetment exhibited effective wave dissipation across a range of surf similarity parameters. It was found to significantly reduce runup when compared to smooth slopes and overall performed more effectively than its more commonly used alternative – the rock armour revetment. This performance is particularly notable as the thickness of the steel-mesh mattress is half that of the rock armour revetment. An apparent difference in dissipation mechanisms was also observed. The steel-mesh revetment exhibited absorption characteristics, whilst the rock armour produced large amounts of turbulence and aeration, indicative of reflection. Overall, steel-mesh cobble/rock revetment proved a successful and effective coastal defence solution under wave conditions. The findings of this study build upon the empirical development and should encourage further research into alternative defence solutions.