Abstract
Abstract. For the UK's longest and most complete sea level record (Newlyn), we assess extreme high waters and their temporal clustering; prompted by the 2013/2014 winter of storms and flooding. These are set into context against this almost 100-year record. We define annual periods for which storm activity and high sea levels can be compared on a year-by-year basis. Amongst the storms and high tides which affected Newlyn, the recent winter produced the largest recorded high water level (3 February 2014) and five other high water events above a 1 in 1-year return period. The large magnitude of tide and mean sea level, and the close inter-event spacings (of large return period high waters), suggests that the 2013/2014 extreme high water level "season" can be considered the most extreme on record. However, storm and sea level events may be classified in different ways. For example, in the context of sea level rise (which we calculate linearly as 1.81 ± 0.1 mm yr−1 from records between 1915 to 2014), a lower probability combination of surge and tide occurred on 29 January 1948, whilst the 1995/1996 storm surge season saw the most high waters of ≥ the 1 in 1-year return period. We provide a basic categorisation of the four types of extreme high water level cluster, ranging from consecutive tidal cycles to multiple years. The assessment is extended to other UK sites (with shorter sea level records and different tide-surge characteristics), which suggests 2013/2014 was particularly unusual. Further work will assess clustering mechanisms and flood system "memory".
Highlights
Extreme sea levels and accompanying coastal floods are known globally for their devastating impacts, in regions exposed to large storm surges which are densely populated and low-lying (e.g. Gönnert et al, 2001; Hanson et al, 2011)
When the high water time series is linearly offset for mean sea level (MSL) changes there are 147 occasions when high water has equalled or exceeded the 1 in 1-year return period at Newlyn
In this paper we have focused on an assessment of the high waters at Newlyn over the past 100 years that are ≥ the 1 www.ocean-sci.net/10/1031/2014/
Summary
Extreme sea levels and accompanying coastal floods are known globally for their devastating impacts, in regions exposed to large storm surges which are densely populated and low-lying (e.g. Gönnert et al, 2001; Hanson et al, 2011). In the last decade there have been several devastating events, including the two most costly natural disasters in US history: Hurricane Katrina which destroyed large swathes of New Orleans and other parts of the Gulf Coast in late Augustearly September 2005 with coastal floods killing more than 800 people (RMS, 2005; Jonkman et al, 2009); and Hurricane Sandy which hit the New Jersey shoreline on 29 October 2012, killing more than 100 people, generating the worst flooding in New York since records began in the 1920s, and causing an estimated USD 50 billion damage (Neria and Shultz, 2012). In November 2013, Typhoon Haiyan, the most intense storm to ever make landfall, impacted the islands of the central Philippines. This event left nearly 8000 people dead, missing or injured, and damaged or destroyed over 1.1 million houses (LeComte, 2014), much of the impact due to the effects of the storm surge. Extreme sea level events like these are expected to increase in magnitude, frequency and impact due to: increases in mean sea level (Haigh et al, 2010a; Wahl et al, 2011); possible changes in storminess (Church et al, 2013); and continued
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