Sediment-deficit sink-zone morphodynamics in oceanic island dune systems: integration of field data and remote sources in the Macaronesian Region

Abstract

Coastal erosion has become a significant problem in the context of global warming and sea level rise. The combination of these factors which, in some cases, produces sedimentary deficit, is causing flooding problems that affect coastal ecosystems such as dune systems. This problem is of particular concern in the context of oceanic islands, where sandy coasts and dune systems are considered to be of significant value. As terminal areas of encapsulated sedimentary systems, sink areas are subject to the downwind effects of current and historical management and uses developed throughout the entire system. The objective of this research is to analyze the evolution of the Sink Zones (they mainly demonstrate behaviors akin to those exhibited by beaches), in various dune systems in Macaronesia, with a particular focus on the Canary Islands (Maspalomas in Gran Canaria, Jandía in Fuerteventura and La Graciosa Island) and Cabo Verde (Costa Fragata-Ponta Preta in Sal Island). A multiscale spatio-temporal approach was employed, utilizing historical and contemporary orthophotos and topographic data (obtained from LiDAR flights with airplanes and photogrammetric flights with drones) to analyze the evolution of the coastline using DSAS software (version 6.0). In the specific instance of the island of La Graciosa, these data were integrated with detailed fieldwork data on wind conditions and sediment characterization. This methodology was utilized to ascertain the morphodynamical response of the aforementioned Sink Zones. The results obtained from the analyses reveal the presence of erosion processes, thus prompting a comprehensive discussion concerning the management and utilization of these natural systems, in addition to the potential impact of climate change.