Abstract
Along many Mediterranean coasts, the detached seagrass material of Posidonia oceanica creates seagrass berms that control the structure and morphodynamics of sandy beaches. Here, we show how Terrestrial Laser Scanner remote sensing data allows analyzing the 3-D morphologic change of beaches where this characteristic geomorphic structure is present. We propose a methodology for estimating accretion/erosion (almost −200 m3 in our study) by considering the sand dominated and seagrass berms as two independent elements. For this purpose, two different sampling dates (named scenarios A and B, before and after an erosive heavy storms period, respectively) recorded in a microtidal pocket-beach (300 m2) with these characteristic geomorphic structures have been modeled in 3-D. The present approach constitutes a cost-efficient, accurate, and quick tool to survey the sand volume in natural and artificial replenished beaches. The innovative approach, which can be considered as a conceptual and methodological starting point, can be useful to examine long-term and high-precision data sets in future studies of the morphodynamic evolution of these characteristic Mediterranean beaches.
Highlights
IntroductionThe morphodynamics of sandy beaches depend on a set of variables, such as sediment granulometry, breaker wave climate (wave height and period), tide range, and major topographic features (beach slope and embayment shape) [1]
The morphodynamics of sandy beaches depend on a set of variables, such as sediment granulometry, breaker wave climate, tide range, and major topographic features [1]
These accumulations of this detached material are referred as seagrass berms [7], they have been named in the scientific literature as beach-cast, beach wrack, or beach strand [8], or “banquettes” according to the French naming [9,10,11]
Summary
The morphodynamics of sandy beaches depend on a set of variables, such as sediment granulometry, breaker wave climate (wave height and period), tide range, and major topographic features (beach slope and embayment shape) [1]. The morphology and water circulation of a beach can be influenced by detached seaweed and seagrasses, which can be accumulated, forming patches and wrack banks on the beach [2,3,4,5,6]. The maximum heights of the seagrass berms are reached because of severe storms in winter time [15]. Such beach-cast accumulations create berm structures along the coast with heights ranging from a few centimetres to several meters and with heterogeneous spatial distribution [11]
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