Rocks vs reefs: assessing biodiversity net gain on a groyne in the UK
Type:
Presented during:
CEDA Dredging Days 2026
Authors:
R. Free, S. Haage and E. Ortelee
Abstract
Boskalis, in collaboration with the local council, reef innovators, and ecologists, developed an environmental enhancement scheme to boost biodiversity at Hengistbury Head, Southern England. Integrated into the renewal of a groyne and designed to reduce coastal erosion in this dynamic environment, the scheme comprised 98 tailored reef units, including various designs of 7-tonnes heavy artificial reefs, artificial tidal pools, and on-site fabricated rock pools. These designs were customised to suit local marine conditions, with pilot projects and physical scale modelling validating their ecological performance and structural stability. Installed in 2024 along and within the groyne, the reefs aim to connect subtidal habitats to the shoreline and increase biodiversity along the groyne. The installation process required detailed operational planning to ensure successful integration. A multi-year monitoring programme, using both conventional and innovative methods (eDNA), provides insights into the biodiversity of the reefs compared to traditional rock armour; and compares the effectiveness of different monitoring methods in a dynamic and challenging environment. Data collected over the course of a year will validate performance for reef innovators and provide local councils and governments with proven, quantified solutions for coastal infrastructure projects. Preliminary results indicate biodiversity increases across multiple reef types, with variations linked to seasons and designs. First-year results will be analysed in the coming month. This project offers a contractor's perspective on integrating artificial reefs into coastal infrastructure, provides a quantification on biodiversity increase of reefs and rock, and demonstrates how biodiversity targets can be translated into practical, real-world approaches