Satellite derived shorelines at an Eexposed meso-tidal beach

Shoreline position data offer extremely valuable information for understanding coastal dynamism and beach changes. This research applies SHOREX system for defining the shoreline position from free mid-resolution Landsat-8 (L8) and Sentinel-2 (S2) satellite imagery. This system allows an automatic definition of Satellite Derived Shorelines (SDS) over large regions and periods. Accuracy and utility of the resulting SDS have been previously assessed with positive results at low energy, microtidal, Mediterranean beaches. This work assesses SDS extracted using SHOREX at a mesotidal and moderate to highly (during storms) energetic environment, namely at Faro Beach, a barrier beach located in Ria Formosa (Algarve, South Portugal). Accuracy was defined for 14 SDS derived from S2 and 10 from L8 by measuring the differences in position with respect to the shoreline inferred from profiles obtained on close dates (or simultaneously) to imagery acquisition. For non-simultaneous datasets, the water level was estimated for the time of the satellite images acquisition using oceanographic data and run-up formulations. The measured and estimated shoreline positions were then compared with the extracted SDS. The overall accuracy is good, with errors about 5 m RMSE, supporting the application of the used methodology to define shoreline dynamics and evolution at challenging environments, as mesotidal exposed and dynamic beaches.Spanish Ministry of Economy and Competitiveness [CGL2015-69906-R]; Spanish Ministry of Education, Culture and Sports [FPU15/04501]info:eu-repo/semantics/submittedVersio

Applied Geography

[EN] Lakes with strong variations in their water coverage may act as in dicators of different natural phenomena. Recent techniques for the extraction of Satellite-Derived Shorelines (SDSs) with subpixel accuracy are potentially useful for accurate and continuous monitoring of the limits of water bodies along large periods. This work proposes a method for combining the shoreline position with a digital elevation model to assign elevation values to the points defining the SDSs along the period 1984¿2020 in the shallow Gallocanta Lake (NE Iberian Peninsula). The relationship between the water surface and the elevation allows modeling the phenomena of lake changes as well as an estimation of the volume. The obtained data enables analyzing size and elevation changes of the water surface and the volumetric changes of the lake over more than three decades with a sub-weekly frequency (2¿5 days). The results constitute a valuable data package for robust analysis of lake trends. In the short term, the methodology provides sufficient precision to capture the changes caused by single meteorological events such as rainfall, even of small magnitude. The method constitutes a novel approach for curate hydric monitoring of lakes and water bodies, along large terrtories without requiring continuous in situ data acquisition.Support This research has been supported by the projects 'Monitorizacion de precision de las fluctuaciones de agua de humedales salinos intermitentes RAMSAR en la cuenca media del Ebro mediante teledeteccion espacial' with the financial support of Fundacion Biodiversidad from the Spanish Ministry for Ecological Transition and the Demographic Challenge (MITECO), PCI2018-092999 (AQUASALT) funded by MCIN/AEI/10.13039/501100011033 and co-funded by European Union, AQ-01.2021 (IRENE) funded by the Government of Aragon, MONOBESAT (PID2019-111435RB-I00) funded by the Spanish Ministry of Science, Innovation and Universities, and the Margarita Salas contract within the Re-qualification programme by the Spanish Ministry of Universities financed by the European Union-NextGenerationEU. This is a contribution to Research Group RNM 328 of the Andalusian Research Plan (PAI), and to CSIC Interdisciplinary Thematic Platform (PTI) Tele-deteccion (PTI-TELEDETECT). ESA and USGS provided access to the satellite imagery. The Spanish Meteorological Agency (AEMET) provided data after contract no. L2990130734. The Ebro River-Basin Authority (CHE) provided the water level data.Palomar-Vázquez, J.; Cabezas-Rabadán, C.; Castañeda, C.; Gracia, FJ.; Fernández-Sarría, A.; Priego De Los Santos, E.; Pons Crespo, R.... (2022). Inferring volumetric changes at a shallow lake from subpixel satellite-derived shorelines. Applied Geography. 149(102792):1-10. https://doi.org/10.1016/j.apgeog.2022.10279211014910279

Shoreline contour, water level elevation and volumetric dataset (1984-2020) for the Gallocanta Lake (NE Spain)

Gallocanta is the largest well-preserved saline lake in Western Europe, included in the Ramsar List. Associated with its shallow morphology, the lake undergoes strong variations in its water surface extent along time that condition the habitat distribution and the ecological functions. Data on the morphology of the lake and its hydrological variations along time may be of paramount ecological importance for the managers of this natural space. Even though its interest for research and management purposes, no accurate and robust dataset of this nature covering large periods of time is available. This dataset presents a multi-decadal mapping with a sub-weekly frequency (2-5 days) of the contour of the Gallocanta Lake (NE Iberian Peninsula) along the period 1984-2020 (1043 dates with information). The shoreline position appears continuously defined with subpixel accuracy from the freely-available images acquired by the satellites Sentinel-2 (sensor MSI) and Landsat 5 (TM), 7 (EMT+), and 8 (OLI) by applying the extraction system SHOREX. The satellite-derived shorelines allow the definition of the surface of the lake and are combined with a digital elevation model to assign elevation values to the points defining each shoreline. This allows deducing the mean elevation of the water level and the volumetric changes for those same dates. This data package constitutes a valuable source of information for carrying out robust analyses of the trends of the lake along decades, as well as its response to individual rainfall events