Spatial and Temporal Clustering Analysis of Extreme Wave Events around the UK Coastline

Victor Malagon Santos,Thomas Wahl,Ivan Haigh

doi:10.3390/jmse5030028

Abstract

Densely populated coastal regions are vulnerable to extreme wave events, which can cause loss of life and considerable damage to coastal infrastructure and ecological assets. Here, an event-based analysis approach, across multiple sites, has been used to assess the spatial footprint and temporal clustering of extreme storm-wave events around the coast of the United Kingdom (UK). The correlated spatial and temporal characteristics of wave events are often ignored even though they amplify flood consequences. Waves that exceeded the 1 in 1-year return level were analysed from 18 different buoy records and declustered into distinct storm events. In total, 92 extreme wave events are identified for the period from 2002 (when buoys began to record) to mid-2016. The tracks of the storms of these events were also captured. Six main spatial footprints were identified in terms of extreme wave events occurrence along stretches of coastline. The majority of events were observed between November and March, with large inter-annual differences in the number of events per season associated with the West Europe Pressure Anomaly (WEPA). The 2013/14 storm season was an outlier regarding the number of wave events, their temporal clustering and return levels. The presented spatial and temporal analysis framework for extreme wave events can be applied to any coastal region with sufficient observational data and highlights the importance of developing statistical tools to accurately predict such processes.

Highlights

Waves are a key process influencing coastal flooding, morphology, and nearshore ecology [1]
We address the following four objectives: (1) compare the dates and return periods of the extreme wave events recorded around the United Kingdom (UK); (2) assess the spatial characteristics of the wave events around the coast, distinguishing different types of footprints of events and examining the categories and tracks of the weather systems responsible for their generation; (3) investigate the temporal variation in events over different time-scales and in particular the clustering nature of extreme storm-wave events; and (4) examine these characteristics for the exceptional 2013/14 storm season
Comparing all storm events in terms of their highest return period across all sites, we found that 43 of the distinct 92 storm events led to wave heights around the UK with maximum return periods ranging from 1 to 2 years, 22 from 2 to 5 years, and 27 had a return period that exceeded 5 years (Figure 3)

Summary

Introduction

Waves are a key process influencing coastal flooding, morphology, and nearshore ecology [1]. Understanding wave climate and probabilities of extreme events is crucial for offshore operators. Flooding and coastal erosion due to extreme waves and storm surges are a major hazard for coastal populations [4], as they are capable of causing extensive economic, cultural, and environmental damage, and can be associated with high mortality [5]. A combination of high water levels (caused by spring tides and storm surges) together with waves is the primary factor leading to coastal flooding. Those combined processes can cause loss of life, and damage to property and the environment by overtopping coastal defenses and inundating low-lying areas [6]. Spatial characterization of wave processes becomes essential to manage coastal hazards effectively

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