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

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 areas covered an area of c.a. 35km (super 2) , at mean water depths (mwd) between 20 and 42 meters were surveyed using multibeam, sub-bottom profiler, ultra-high resolution multichannel seismics and a set of 126 surface samples and 72 (3 meters long) vibrocores. 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 archeological artifacts. The adopted methodology proved to be adequate to quantify and describe the spatial distribution of useful sediment volumes, supporting a strategy of coastal sections sedimentary management in the medium-long term. Supplementary material at https://doi.org/10.6084/m9.figshare.c.5007266