Climate forcing of regionally-coherent extreme storm impact and recovery on embayed beaches

Abstract

The effective management of sedimentary coastlines demands a good understanding of the seasonal and inter-annual cycles in beach volumes, as well as the potential impact of extreme events. This paper uses a 10-year time series (2007-2017) of supra-and intertidal beach volume from exposed and cross-shore transport-dominated sites to examine the extent to which beach behaviour is coherent over a relatively large region (100-km stretch of coast) and predictably coupled to incident wave forcing. Over the study period, 10 beaches, exposed to similar wave/tide conditions, but having different sediment characteristics, beach lengths and degrees of embaymentisation, showed coherent and synchronous variations in sediment volumes, albeit at different magnitudes. The sequence of extreme storms of the 2013/14 winter, which represents the most erosive event over at least a decade along most of the Atlantic coast of Europe, is included in the data set, and three years after this winter, beach recovery is still ongoing for some of the beaches. Poststorm beach recovery was shown to be mainly controlled by poststorm winter wave conditions, while summer conditions consistently contributed to modest beach recovery. Skilful hindcasts of regional changes in beach volume were obtained using an equilibrium-type shoreline model (ShoreFor; Davidson et al., 2013), demonstrating that beach changes are coherently linked to changes in the offshore wave climate and are sensitive to the antecedent conditions. The ShoreFor model can successfully be applied to exposed coastal areas dominated by cross-shore sediment transport, and can also be used as a relatively simple and regional tool for the future management of beaches where coherence in coastal response is observed. Furthermore, a good correlation was found between the beach volume changes and the new climate index WEPA (West Europe Pressure Anomaly; Castelle et al., 2017b), which offers new perspectives for the role and the use of climatic variations proxies to forecast coastline evolution. response to annual variations in incident wave height and period

Beach recovery from extreme storm activity during the 2013–14 winter along the Atlantic coast of Europe

“…They found that the recovery mechanisms and timescales were highly dependent on the site characteristics, and that high-energy wave events were essential for the recovery of sediments. Burvingt et al (2018) found that for a number of very similar beaches in southwest England recovery from the 2013-14 storm was regionally coherent, multi-annual (>3 years) and mainly controlled by winter-wave conditions. Castelle et al (2017a) investigated how the beach-dune system of an exposed site in southwest France recovered from winter 2013-14 and found that only after 1.5 years the beach-dune system almost fully recovered to its pre-winter volume.…”

“…Burvingt et al. () found that for a number of very similar beaches in southwest England recovery from the 2013–14 storm was regionally coherent, multi‐annual (>3 years) and mainly controlled by winter‐wave conditions. Castelle et al.…”

“…Unfortunately, such monitoring programmes are scarce, and the few available datasets have been used mostly to characterize extreme storm responses (Scott et al, 2016;Barnard et al, 2017), investigate the parameters controlling beach morphological changes (Yates et al, 2011) and develop semi-empirical equilibrium models able to reproduce these morphological changes (Davidson and Turner, 2009;Yates et al, 2009;Splinter et al, 2014). However, ongoing field monitoring programmes in France and the UK have recently shed some lights on the key mechanisms involved during post-storm recovery (Scott et al, 2016;Castelle et al, 2017a;Burvingt et al, 2018). Scott et al (2016) investigated the morphological changes at three contrasting sites in southwest England during the 2 years that followed the extreme 2013-14 winter.…”

Modes of Berm and Beachface Recovery Following Storm Reset: Observations Using a Continuously Scanning Lidar

“…Additionally, during recovery the “usable” width of a beach is restored to satisfy beach goers (Frampton, ) and impacted beach ecology returns to its former state of health (Revell et al, ). While studies have developed empirical and process‐based understanding of storm erosion (e.g., Larson & Kraus, ; Roelvink et al, ), insight into beach recovery and the physical parameters governing the rebuilding of subaerial beach profile is less well observed and understood (e.g., Burvingt et al, ; Corbella & Stretch, ; Dodet et al, ; Jensen et al, ).…”

“…The rebuilding of the berm and beachface by swash processes marks the most landward extent of wave‐driven processes during beach recovery, beyond which more gradual aeolian processes rebuild eroded morphology in the backshore and dunes (Morton et al, ). The majority of previous investigations of swash‐driven beachface (i.e., seaward of the berm crest and extending to mean sea level, MSL) and berm (i.e., landward of the berm crest and seaward of the foredune toe) morphodynamics during recovery are limited by the temporal resolution of poststorm morphology data sets which typically capture morphological and volumetric changes during recovery at monthly to yearly timescales (e.g., Burvingt et al, ; Castelle et al, ; Corbella & Stretch, ; Houser et al, ; Kobayashi & Jung, ; Morton et al, ; Scott et al, ; Yu et al, ).…”