Maintaining a way of life for São Miguel Island (the Azores archipelago, Portugal): An assessment of coastal processes and protection

Traditional hard engineering structures and recently emerging soft engineering alternatives have been employed to protect vulnerable coastlines. Despite negative publicity, they have ensured community survival where socio-economic benefits outweigh adverse impacts. This is especially true for Small Islands (SI) where increasing sea levels and storm intensities threaten already limited land availability. This paper presents coastal vulnerability in São Miguel Island (the Azores SI archipelago) and considers SI issues with regard to coastal land loss. Regional wave statistics using 1998 to 2011 wind record showed: periods ranging from 7 to 13 s (circa 83%); wave heights between 1 and 3 m (circa 60%); and increasing trends in westerly (p = 0.473), easterly (p = 0.632) and southeasterly (p = 0.932) waves. Sea level analyses between 1978 and 2007 indicated a statistically significant rising trend (2.5 ± 0.4 mm yr− 1; p = 0.000), while between 1996 and 2007 it was 3.3 ± 1.5 mm yr− 1 (p = 0.025), agreeing with other global sea level studies. Based on 2001 and 2008 population data and using zonal statistics, circa 60% of the Island's population was found to reside within 1 km of the sea and the percentage of total population was linearly correlated with distance from the shoreline (r2 = 99%). Three case studies show hard coastal engineering solutions preserved Azorean coastal lifestyle and had little or no observed negative impacts on their environs. Although hard engineering is likely to remain a valuable and feasible coastal protection option, an inventory of São Miguel's population distribution, surf breaks, bathymetry and coastal erosion rates showed the potential of using multifunctional artificial reefs as a soft engineering solution. These offshore submerged breakwaters offer coastal protection while providing additional benefits such as surfing amenity and beach widening. Consequently, findings of this work can inform other SI communities.