Ecological study on foreshore sand suppletion at the Flemish coast (4SHORE)

What ecological effects on the Belgian coast does a foreshore suppletion (creating an underwater sand buffer) have on the marine ecosystem in the shallow surf zone (1-2 m depth)? This project provides scientific support for the Belgian Master plan for Coastal Defense. Beach suppletions and other coastal defense works are planned along the Belgian coast to safeguard the coastal inhabitants. In this plan, the authorities are exploring new, more efficient, and more ecological ways of coastal defense. Foreshore suppletion in the shallow coastal zone, which prevents adverse beach erosion, is one of the options being explored. By means of an experimental set-up in a part of the Belgian coastline, we get insight into the possible environmental effects and we can assess the ecological value of foreshore suppletion.

The governmental coastal agency organises an experimental test of foreshore suppletion at Mariakerke (Oostende). A buffer of 400.000m³ fine sand is placed in the shallow coastal zone there (-1 to -2m TAW, surf zone). We collect biological and sedimentological samples in the impact area (Mariakerke) and in a control area (Bredene),  before (T0) as after (T1, T2) the suppletion, to evaluate the effect of the suppletion on the marine ecosystem. We monitor the marine ecosystem with a focus on the fauna within the sediment (macrofauna) and on the sediment (hyperbenthos, epi- and demersal fish fauna) in the intertidal zone (beach) and subtidal zone (0 to -6m TAW). Based on the data gathered, we determine the ecological value of the area, the recovery capacity of the fauna  present and the influence of the activity on the functioning of the ecosystem. Finally, we transform our findings into well-founded ecological recommendations for the agency in question.

This study clarifies in which way foreshore suppletions can contribute in the near future to the ‘natural’ coastal safety in harmony with nature management. The ecological functioning of the beach and surf zone as parts of the coastal foundation is not yet fully understood. We expect that this study will provide objective and scientific support for the debate on the potential impact of sand suppletions on the natural value of the Belgian coast. During this study, we apply benthic indicators as tool for the environmental assessment and we use the data to further develop the predictive model of suppletion effects (developed by Ghent University's Marine Biology group). Those tools are important and reliable supporting tools for government authorities.