Assessment and comparison of extreme sea levels and waves during the 2013/14 storm season in two UK coastal regions

Abstract

Abstract. The extreme sea levels and waves experienced around the UK's coast during the 2013/14 winter caused extensive coastal flooding and damage. Coastal managers seek to place such extremes in relation to the anticipated standards of flood protection, and the long-term recovery of the natural system. In this context, return periods are often used as a form of guidance. This paper provides these levels for the winter storms, and discusses their application to the given data sets for two UK case study sites: Sefton, northwest England, and Suffolk, east England. Tide gauge records and wave buoy data were used to compare the 2013/14 storms with return periods from a national data set, and also joint probabilities of sea level and wave heights were generated, incorporating the recent events. The 2013/14 high waters and waves were extreme due to the number of events, as well as the extremity of the 5 December 2013 "Xaver" storm, which had a high return period at both case study sites. The nationalscale impact of this event was due to its coincidence with spring high tide at multiple locations. Given that this event is such an outlier in the joint probability analyses of these observed data sets, and that the season saw several events in close succession, coastal defences appear to have provided a good level of protection. This type of assessment could in the future be recorded alongside defence performance and upgrade. Ideally other variables (e.g. river levels at estuarine locations) would also be included, and with appropriate offsetting for local trends (e.g. mean sea-level rise) so that the storm-driven component of coastal flood events can be determined. This could allow long-term comparison of storm severity, and an assessment of how sea-level rise influences return levels over time, which is important for consideration of coastal resilience in strategic management plans.

Impacts of storm chronology on the morphological changes of the Formby beach and dune system, UK

“…2 together with the storm threshold wave height used to calculate the offshore storm wave power. In the first event (D1), which persisted about 1 day, the peak storm wave height (4.6 m) coincides with high water (6.2 m ODN) during spring tide and strong westerly wind (note: wind characteristics are not shown here but are presented by Wadey et al, 2015). The second storm (D2) spanned about 19 h and occurred during the intermediate period between spring and neap tide.…”

“…1). Using records of waves and water levels the recent storm cluster of December 2013-February 2014 has been found to consist of some of the most extreme conditions this coastline has experienced (Wadey et al, 2015). We therefore use this cluster of events to investigate how the chronology of wave events, with different wave power, causes variability in the system resilience to extreme events and the cumulative erosive impact on Formby Point.…”

The extant shore platform stromatolite (SPS) facies association: a glimpse into the Archean?

“…The Irish and Scottish coasts are known for strong wave action (Hall et al, 2006;O'Brien et al, 2013) as the 2013-2014 storm season proved (Wadey et al, 2015). Both Giant's Causeway (on the west coast) and Luskentyre Bay are afforded some protection, but the boulder storm beaches at both localities (Table 2) have shown themselves to be vulnerable to wave attack.…”

Role of Beach Morphology in Wave Overtopping Hazard Assessment

“…The univariate probabilities for the water level and wave heights were calculated as 1:44 year and 1:5 year, respectively. This extreme event may have exceeded 1:200 year when considered in joint probability [49]. Given that this event caused significant wave overtopping and the breaching of a secondary sea defence, a 1:200 year WL and the values extracted from our joint probability analysis can be considered appropriate in addressing our research aims.…”