Abstract
Sediment grain size is a fundamental parameter conditioning beach-face morphology and shoreline changes. From remote sensing data, an efficient definition of the shoreline position as the water–land interface may allow studying the geomorphological characteristics of the beaches. In this work, shoreline variability is defined by extracting a set of Satellite Derived Shorelines (SDS) covering about three and a half years. SDS are defined from Sentinel 2 imagery with high accuracy (about 3 m RMSE) using SHOREX. The variability is related to a large dataset of grain-size samples from the micro-tidal beaches at the Gulf of Valencia (Western Mediterranean). Both parameters present an inverse and non-linear relationship probably controlled by the beach-face slope. High shoreline variability appears associated with fine sands, followed by a rapid decrease (shifting point about medium/coarse sand) and subsequent small depletions as grain sizes increases. The relationship between both parameters is accurately described by a numerical function (R2 about 0.70) when considering samples at 137 open beaches. The definition of the variability is addressed employing different proxies, coastal segment lengths, and quantity of SDS under diverse oceanographic conditions, allowing to examine the effect they have on the relation with the sediment size. The relationship explored in this work improves the understanding of the mutual connection between sediment size, beach-face slope, and shoreline variability, and it may set up the basis for a rough estimation of sediment grain size from satellite optical imagery.
Highlights
Beaches are highly dynamic and changing natural environments that provide protection to the coast, habitat for unique species and constitute a basic recreational resource for coastal societies
Taking size along large beach segments from a freely available source of data. Taking this into this into account, the main goal of this work is to characterize the relationship between account, the main goal of this work is to characterize the relationship between sediment sediment size and shoreline variability determined from multiple Sentinel-2 derived size and shoreline variability determined from multiple Sentinel-2 derived shorelines
The median grain size of the beach-face sediment appears related to the shoreline variability in a non-linear way along the grain-size spectrum, with a shifting point at D50 ≈ 0.5 mm
Summary
Beaches are highly dynamic and changing natural environments that provide protection to the coast, habitat for unique species and constitute a basic recreational resource for coastal societies. Sediment size and slope are key geomorphological elements for characterizing the beaches as they appear interrelated with each other and with the oceanographic conditions [1,2,3] These geomorphological aspects condition beach functions by defining the abundance of biota [4], beachgoers perception [5] and safety [6], and beach response to stress factors as storms [7,8,9]. The quantification of sediment grain size by traditional techniques is a time-consuming task that hinders the collection of repetitive data over long coastal segments.
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