Examinando por Autor "Benavente, Javier"

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UAS & SfM-based approach to Monitor Overwash Dynamics and Beach Evolution in a Sandy Spit
(The Coastal Education and Research Foundation (CERF), 2018-05-01) Talavera, Lara; Del Río, Laura; Benavente, Javier; Barbero, Luis; López-Ramírez, J. Antonio
The role of overwash processes is of great relevance in the long-term evolution of sandy barriers, and it can also affect coastal infrastructures in the short term. In this work, a 10-month monitoring program based on the use of Unmanned Aerial Systems (UAS) in combination with Structure from Motion (SfM) algorithms was performed in order to monitor morphological changes and ulterior evolution at Camposoto beach, an overwash-prone coastal spit located in SW Spain. This UAS&SfM approach allowed the reconstruction of 6 Digital Elevation Models (DEMs) of the area with high temporal and spatial resolutions (RMS vertical errors spanning from 5 to 8 cm). The morphological changes occurred were detected using Geomorphic Change Detection Software in ArcGIS, and they were correlated with the oceanographic conditions that prevailed during the analysed period. The results obtained provided insight into the response of the system against storm-induced overwash, which caused significant erosion/accretion patterns over a pre-existing washover fan, as well as the landward migration of the system. In addition, this methodology captured the progressive partial recovery of the system, which included onshore transport of sand, fore-beach accretion, and berm reconstruction. Despite the partial recovery observed, spring tides also triggered non-storm overwash in the area during fair-weather conditions, allowing to rethink the actual vulnerability state of the spit against rollover processes.
UAS as tools for rapid detection of storm-induced morphodynamic changes at Camposoto beach, SW Spain
(Taylor & Francis, 2018-05-10) Talavera, Lara; Del Río, Laura; Benavente, Javier; Barbero, Luis; López-Ramírez, J. Antonio
The increasing pressures and hazards derived from human action and climate change make the implementation of coastal monitoring plans a requirement for assessing coastal responses and evolution. For this reason, this work aims to use unmanned aerial systems (UAS) in combination with Structure from Motion algorithms for detecting morphodynamic changes caused by a storm in Camposoto beach (SW Spain). This approach provided pre- and post-storm digital elevation models of the study area with root mean square vertical errors of 6.89 and 5.54 cm, respectively, that allowed the identification of storm-induced gain and loss of sediment using Geomorphic Change Detection software. Furthermore, it also captured the response of the system against the action of specific marine processes such as storm-induced swash, collision, and overwash. The results obtained highlight the importance of an optimum flight plan design (e.g. the use of 85–75% front and side image overlap, respectively) and enhance the suitability of the UAS technology to satisfy the demands and needs in coastal monitoring studies in comparison with the traditional techniques, namely aerial photogrammetry, satellite imagery, and/or light detection and ranging.
UAS-based High-resolution Record of the Response of a Seminatural Sandy Spit to a Severe Storm
(The Coastal Education and Research Foundation (CERF), 2020-05-26) Talavera, Lara; Del Río, Laura; Benavente, Javier
Human infrastructures in barrier islands restrict the natural storm-induced overwash needed by these systems toevolve, further increasing their vulnerability in the medium and long term. For this reason, accurate overwashmeasurements in coastal environments subject to varying degrees of occupation are needed. In this work, twoUnmanned Aerial System (UAS) flights were performed over two distinct sectors of a sandy spit located inCádiz (SW Spain) prior and after the landfall of storm Emma. This storm was a high-energy event that lasted153 hours,with an average significant wave height of 4 m and a storm peak of 6.81 m., and water levels (tideand surge) of up to 4 m. The images derived from the UAS flights were processed with Structure From Motion(SfM) algorithms using Pix4D software, resulting in high-resolution mosaics and Digital Elevation Models(DEMs) of the study area. These allowed (1) the digitization of the washover deposits in both sectors beforeand after the storm, and (2) the computation of DEMs of Difference (DoDs), which in turn allowed the analysisof volumetric estimates of erosion/accretion triggered by the significant overwash. The results revealed a non-uniform coastal response between both sectors. The area subject to higher degree of development showed aclear restriction in the onshore delivery of sediment during overwash due to the presence of a channel and aroad, the coalescence of the nine pre-existing washovers into a unique deposit of 77546 m 2, and much higherdamage extents and associated recovery costs. In the natural sector, the overwash processes reactivated thethree pre-existing washovers (which enlarged their areas up to 200%) with no significant damages reported.These findings serve as examples of coastal responses to future similar hydrodynamic conditions, and suggestthat this spit will likely evolve following different trajectories in the long-term.