Using multi-scale spatio-temporal shoreline analysis of an urban beach adjacent to a basin system on an oceanic island for its integrated planning

Abstract

The increasing littoralization process of coastal areas in recent decades to adapt them to user needs has generated important changes in ecosystems. This is the case of the coast of Tazacorte (Canary Islands, Spain) where the construction of a port in the 1970s caused changes to the coastal dynamics that allowed the appearance of a sandy beach as a result of contributions made by ravines and beach nourishment actions. In this context, the aim of this article is to carry out an analysis of the current situation of the beach and better understand its relationship with local ravines and the effects of recently constructed infrastructure. The management measures that have been executed to date are discussed and new measures are proposed. The methodology combines field work, variation of shorelines, LiDAR analysis and marine and atmospheric climate characterization. The results show a clear difference between the processes analysed in the long term where the variation in shoreline, beach area and volume indicate a positive trend (between 17.64 and 151.05 m, from 15,060 to 67,096 m2 and from 141,564 to 630,674m3 respectively), and which is mainly explained by the role of infrastructures (breakwaters and port), however, a short-term analysis from 2009 to 2020, the results show that the beach and the seafront continue to flood as a consequence of marine storms and runoff from the gullies, despite the inputs made the negative trend and an irregular behaviour, that is, years with a volume of 689.966 m3 in 2010 and years with 604,096 m3 in 2014. In this sense, the natural dynamics of the beach are discussed against a beach management that costs approximately 45,000 euros per year and requires continuous work during the winter and spring. Therefore, this research, through the management measures it proposes, aims to increase its natural resilience to extreme events from a long-term point of view.