Seeking harmony in coastal development for small islands: Exploring multifunctional artificial reefs for Sao Miguel Island, the Azores

Abstract

The Azores is a remote archipelago rich in biodiversity, geodiversity and cultural heritage located in the middle of the North Atlantic Ocean. It comprises nine volcanic Small Islands (SIs) scattered over 600 km and are vulnerable to coastal hazards due to limited land availability and ocean exposure. To mitigate and adapt to hazards and human occupation, traditional hard-engineering structures have been used. However, these structures have negative impacts on natural coastal character and amenity value and with growing environmental awareness, soft-engineering solutions designed to work with natural processes, such as multifunctional artificial reefs (MFARs), are globally becoming more appealing. MFARs are offshore submerged structures which provide coastal protection while enhancing marine and recreational amenities such as surfing, diving and beach widening. This paper determines "optimal" MFAR multifunctional design criteria based on current progress and assessment of nine international MFARs installed to-date. It subsequently explores MFAR feasibility in Sao Miguel Island, the biggest and most populated Azorean Island with the largest surfing population. An assessment of surf breaks was undertaken, including coastal processes and retreat rates, and MFAR site selection, criteria and rationale are discussed. By considering site-specific parameters such as local bathymetry, wave climate, tides, coastal processes and marine environment alongside tourism potential and surf culture, Sao Roque reef was selected as a potential MFAR to provide both coastal protection and surfing amenity.