Monitoring the Morphodynamic Cannibalization of the Rossbeigh Coastal Barrier and Dune System over a 19-Year Period (2001–2019)

Siegmund Nuyts,Jimmy Murphy,Michael O'Shea

doi:10.3390/jmse8060421

Siegmund Nuyts, Jimmy Murphy + Show 1 more

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https://doi.org/10.3390/jmse8060421

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Abstract

This research presents a study on the morphodynamic evolution of the Rossbeigh coastal barrier and its dune system, located in Dingle Bay, County Kerry, Ireland. The study examines the evolution of the system over a 19-year period (2001–2019) through remote sensing, geographic information system (GIS) analysis, and field-based surveys. This research provides an ideal opportunity to examine a natural erosion event, referred to as cannibalization on a coastal barrier and its dune system. Since the beginning of this century, significant erosion has been visible on the coastal barrier, with the erosion eventually leading to a breaching event in the winter of 2008/2009. Over the study period, analysis has shown that the vegetated dunes decreased by more than 60 percent, the width of the breached area reached a maximum width of over 1 km and a change in orientation and appearance on the coastal barrier has been quantified. The analysis identifies a growing drift-aligned zone, contrasted with a reduction in the stable swash-aligned zone. Significantly, the point between these zones (i.e., the hinge point) has been shown to have moved by more than 1 km also. The migration of this hinge point and cannibalization of the dunes are illustrated. Finally, the potential mechanism for beach healing is identified, utilizing the rich datasets collected during the study, thus providing an insight into the long-term behavior of a dynamic coastal barrier system undergoing naturally driven cannibalization.

Highlights

Coastal barriers are narrow, elevated ridges of sand or gravel, often parallel to the shore
This study evaluates the evolution of the dune system on the Rossbeigh coastal barrier over a period of 19 years (2001–2019) with a particular emphasis on the processes prevalent on the coastal barrier and its surrounding coastal cell
Continuous monitoring of the system is important in order to highlight the change over time of a natural breaching event. It is clear from the examination of 19 years of remotely sensed data combined with field measurements that the Rossbeigh coastal barrier was in a post-breaching phase for the majority of the monitoring period

Summary

Introduction

Coastal barriers are narrow, elevated ridges of sand or gravel, often parallel to the shore. The dune systems on sand based coastal barriers play an important role in the coastal environment as they protect the exposed coastlines from open-ocean forcings [1,2,3]. This makes them one of the most vulnerable coastal systems. Breaching events around the world have been widely reported by [4,5,6,7] Often, these breaching events include human intervention in order to re-establish the dune systems, such as mechanical breach closure, beach scraping, and sediment bypassing systems. Understanding the different processes involved after a breaching event occurred is fundamental for an adequate management of coastal barriers and their dune system

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