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Integrated geophysical and sedimentological datasets for assessment of offshore borrow areas: the CHIMERA project (western Portuguese Coast)

2020; Geological Society of London; Volume: 505; Issue: 1 Linguagem: Inglês

10.1144/sp505-2019-100

2041-4927

Mário Mil-Homens, Pedro Brito, V. Magalhães, Marcos Rosa, Marta Neres, Marta Silva, Emı́lia Salgueiro, Teresa Drago, Ana Isabel Rodrigues, Miriam Tuaty-Guerra, Maria José Gaudêncio, Eveline Almeida, Mariana Silva, Mafalda Freitas, Celso Aleixo Pinto, Cidália Bandarra, Pedro Terrinha,

Coastal and Marine Dynamics

Abstract Coastal erosion impact on low-lying sandy shorelines represents a worldwide problem, which is particularly felt in various segments of the Portuguese coast where this geomorphological type represents 42% of its total length. Beach nourishment is a viable engineering alternative for shore protection and the assessment of offshore sources of beach-fill material is an essential aspect when implementing this mitigation strategy. The CHIMERA project carried out a multidisciplinary inspection on four segments of the west Portuguese coast to assess their potential as offshore borrow areas for beach nourishment. Altogether, these segments covered an area of c . 35 km 2 , at water depths between 20 and 42 m. They were surveyed using multibeam, sub-bottom profiler, ultra-high resolution multichannel seismics and a set of 126 surface samples and 72 vibrocores (with 3 m long each). To comply with the Portuguese legislation, sand types were assessed by granulometric and chemical analyses for evaluating the quality of sediments in terms of contamination. High-resolution magnetic surveys were conducted to find potential archaeological artefacts. The adopted methodology proved to be adequate to quantify and describe the spatial distribution of useful sediment volumes, supporting the ongoing Integrated Coastal Sediment Strategy for mainland Portugal.