Impacts of a multi-purpose artificial reef on hydrodynamics, waves and long-term beach morphology

Multipurpose Artificial Reefs (MPARs) are structures placed in the nearshore to protect the coast, enhance surfing conditions and ecology. Narrowneck reef is the first MPAR aimed to protect the coast with secondary goal of enhance surfing. Since then, few other structures such as Narrowneck have been deployed and limited data is available in terms of their performance. This paper looks into the impacts the reef has on hydrodynamics, waves and morphologic changes. The results indicate that the reef acts as a hold point deflecting the longshore currents and changing the sediment pathway which resulted in morphological changes observed over longer term. Whilst expected during the design phase of the reef a long-term salient is not observed in the historical record. The primary reef impacts are observed underwater where an increase of sand volume updrift of the reef is clear. This highlights the importance of analysing the whole profile as opposed to the shoreline changes to assess long-term impact of such nearshore structures.