Assessing Storm Response of Multiple Intertidal Bars Using an Open-Source Automatic Processing Toolbox

Anne-Lise Montreuil,Margaret Chen,Rik Houthuys,Robrecht Moelans,Patrick Bogaert

doi:10.3390/rs14041005

Anne-Lise Montreuil, Margaret Chen + Show 3 more

Open Access

https://doi.org/10.3390/rs14041005

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Abstract

Intertidal bars are common features of sandy beaches in meso- and macro-tidal environments, yet their behaviour under storm impact and subsequent recovery remain poorly documented. Intensive surveys provide valuable information; however, it takes time to process the vast amount of data. This study presents the morphological response of a multibarred macro-tidal beach along the Belgian coast after a severe storm that happened on 8–12 February 2020, and to develop and apply an oPen-source Raster prOcessing Toolbox for invEstigation Coast intertidal bar displacemenT (PROTECT) in Python for automated bar extraction. This toolbox was applied to the digital surface models of pre- and post-storm airborne LiDAR surveys of a multibarred intertidal beach. The PROTECT toolbox is capable of detecting the position and elevation of intertidal bars accurately. The uncertainty in the elevation characteristics of the bars induces an error in the elevation dimension of 0.10 m. Using the toolbox, the results showed that the intertidal bars changed in term of variations in bar number, dimensions and shape across the storm event. Overall, the storm significantly eroded the dune and the upper-beach zone with a sand loss equivalent elevation decrease of −0.14 m. This was followed by a continuous and full recovery after 9 months under fair weather conditions. In contrast, the sand budget in the intertidal zone did not change over the entire monitoring period although the bars showed significant morphological change. Applying the PROTECT toolbox on high-resolution 3D topographic datasets allows to increase the temporal mapping resolution of intertidal bars from long-term (years) to short (storm events) time scales. Similar assessments at locations worldwide would allow the improvement of our knowledge on the morphodynamical role of multibarred beaches and to forecast their evolution, thus contributing to manage future storm response and the progressively accelerating sea level rise.

Highlights

Multiple intertidal bar systems comprise include shore-parallel morphological features characterised by sandy bar crests-troughs
The y-axis corresponds to the beach elevation and the xaxis to the distance from the reference line located seaward. Another common pattern after the storm is that the bars occupied a number of preferential elevational positions across the intertidal beach: inner bar between 3.5–3.7 m TAW, middle bar
This study investigated the severe event Ciara storm, and applied the newly developed PROTECT toolbox to evaluate multibarred beach storm response and post-storm recovery

Summary

Introduction

Multiple intertidal bar systems comprise include shore-parallel morphological features characterised by sandy bar crests-troughs. They are commonly present in low to moderate energy coastal environments (i.e., exposed to fetch-limited waves) characterized by a surplus of sand and tidal ranges larger than about 3 m [1]. Bars are permanent or to semi-permanent features,

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