Monitoring Retreat of Coastal Sandy Systems Using Geomatics Techniques: Somo Beach (Cantabrian Coast, Spain, 1875–2017)

Abstract

The dynamics and evolution of a coastal sandy system over the last 142 years were analyzed using geomatics techniques (historical cartography, photogrammetry, topography, and terrestrial laser scanning (TLS)). The continuous beach-dune system is a very active confining sand barrier closing an estuarine system where damage is suffered by coastal infrastructures and houses. The techniques used and documentary sources involved historical cartography, digitalizing the 5-m-level curve on the maps of 1875, 1908, 1920, 1950, and 1985; photogrammetric flights of 1985, 1988, and 2001 without calibration certificates, digitalizing only the upper part of the sandy front; photogrammetric flights of 2005, 2007, 2010, and 2014, using photogrammetric restitution of the 5-m-level curve; topo-bathymetric profiles made monthly between 1988 and 1993 using a total station; a terrestrial laser scanner (TLS) since 2011 by means of two annual measurements; and the meteorological data for the period of 1985-2017. The retreat of the sandy complex was caused by winter storms with large waves and swells higher than 6 m, coinciding with periods demonstrating a high tidal range of over 100 and periods with a large number of strong storms. The retreat was 8 m between December 2013 and March 2014. The overall change of the coastline between 1875 and 2017 was approximately 415 m of retreat at Somo Beach. The erosive processes on the foredune involved the outcrop of the rock cliff in 1999 and 2014, which became a continuous rocky cliff without sands. To know the recent coastal evolution and its consequences on the human environment, the combined geomatic techniques and future TLS data series may lead to the improvement in the knowledge of shoreline changes in the context of sea level and global changes.

A Methodology to Assess Land Use Development, Flooding, and Wetland Change as Indicators of Coastal Vulnerability

“…The goal was to utilize a variety of readily available data and a combination of geospatial analysis techniques to investigate the relationship between land cover change, urbanization, wetland loss, and potential flooding with respect to how these factors spatially interact. Most studies of this type have focused on a relatively small study area, such as one urban area or a bay/estuary, where the investigation identifies where changes have occurred and computes various metrics (e.g., rate of wetland loss) [30][31][32][33][34][35][36][37][38][39][40]. Conversely, in this project, we investigated a large study area (2281 km 2 ) where we conducted a generalized/regional assessment of the changing environment and investigated a large coastal area (105 km 2 ) in much greater detail using high-resolution data to look for patterns and trends for a variety of factors.…”

Diachronic UAV Photogrammetry of a Sandy Beach in Brittany (France) for a Long-Term Coastal Observatory

“…Furthermore, this example raises several questions about the influence of various parameters, notably, the prior beach state, the proportion of the change in sediment budget that is due to recent variations (during the last few days) or the influence of the dates of survey, and the period considered in the DoD. In Porsmilin Beach, the goal is to produce at least two high-resolution DEMs per year combining UAV and TLS surveys, so as to capture winter and summer periods, as in [30]. For a long-term observatory, despite the flexibility offered by UAV surveys nowadays, it seems difficult, both in terms of the time required for data acquisition and processing and of the required storage capacities, to carry out more than two or three flights per year, especially if more than one site is being monitored.…”

Comment on nhess-2021-16

“…Almost 200 of them, mainly rocky cliffs, belong to the Asturias region, where slope instabilities are frequent (Valenzuela et al, 2017;Domínguez-Cuesta et al, 2018a;2018b). There are numerous studies focused on the loss of sand or the general evolution of the Cantabrian coast beaches (Flor and Flor-Blanco, 2005;Flor-Blanco et al, 2015;Blasco et al, 2018), but few are focused on the characterization of the rocky cliffs retreat (Domínguez-Cuesta et al, 2020a;2020b). However, some previous works have obtained average retreat rates of 0.57 m year -1 for the period 2006-2017, reaching rates up to 1.22 and 2.19 m year -1 near the town of Luanco, in the surroundings of Peñas Cape (Domínguez-Cuesta et al, 2020a).…”