摘要：Coastal flooding is a major global hazard, yet fewstudies have examined the spatial and temporal characteristics of extremesea level and associated coastal flooding. Here we analyse sea-level recordsaround the coast of New Zealand (NZ) to quantify extreme storm-tide andskew-surge frequency and magnitude. We identify the relative magnitude ofsea-level components contributing to 85 extreme sea level and 135 extremeskew-surge events recorded in NZ since 1900. We then examine the spatial andtemporal clustering of these extreme storm-tide and skew-surge events andidentify typical storm tracks and weather types associated with the spatialclusters of extreme events. We find that most extreme storm tides weredriven by moderate skew surges combined with high perigean spring tides. Thespring–neap tidal cycle, coupled with a moderate surge climatology,prevents successive extreme storm-tide events from happening within 4–10 d of each other, and generally there are at least 10 d between extremestorm-tide events. This is similar to findings from the UK (Haigh et al.,2016), despite NZ having smaller tides. Extreme events more commonlyimpacted the east coast of the North Island of NZ during blocking weathertypes, and the South Island and west coast of the North Island during troughweather types. The seasonal distribution of both extreme storm-tide andskew-surge events closely follows the seasonal pattern of mean sea-levelanomaly (MSLA) – MSLA was positive in 92 % of all extreme storm-tide events andin 88 % of all extreme skew-surge events. The strong influence oflow-amplitude (−0.06 to 0.28 m) MSLA on the timing of extreme events showsthat mean sea-level rise (SLR) of similarly small height will drive rapidincreases in the frequency of presently rare extreme sea levels. Thesefindings have important implications for flood management, emergencyresponse and the insurance sector, because impacts and losses may becorrelated in space and time.
