Decision makers face challenges in coastal areas about how to address the effects of ongoing and uncertain sea-level rise. Dynamic adaptive pathways planning (DAPP) and Real Options Analysis (ROA) can support decision makers to address irreducible uncertainties in coastal areas. This paper sets out what we learned by complementing multi-criteria decision analysis with DAPP and ROA when developing a 100-year coastal adaptation strategy in Hawke’s Bay, New Zealand. Lessons include the value of collaborative community and decision maker processes for increasing understanding about the changing risk over time, and the need to take early actions that enable a shift in pathway before those actions become ineffective. Modifications to the methods highlighted the importance of using several plausible scenarios for stress-testing options; considering costs and consent-ability early, to avoid the perception that hard protection will last; which criteria are appropriate for communities to assess; and making many pathways visible for future decision makers. We learned about the difficulties shifting thinking from short-term protection actions to longer-term anticipatory strategies. We found that a pathways system will require ongoing political leadership and governance with monitoring systems that can manage the adaptive process over long timeframes, by governments and their constituent communities.

Coastal flooding is a major global hazard, yet few studies have examined the spatial and temporal characteristics of extreme sea level and associated coastal flooding. Here we analyse sea-level records around the coast of New Zealand (NZ) to quantify extreme storm-tide and skew-surge frequency and magnitude. We identify the relative magnitude of sea-level components contributing to 85 extreme sea level and 135 extreme skew-surge events recorded in NZ since 1900. We then examine the spatial and temporal clustering of these extreme storm-tide and skew-surge events and identify typical storm tracks and weather types associated with the spatial clusters of extreme events. We find that most extreme storm tides were driven by moderate skew surges combined with high perigean spring tides. The spring–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 extreme storm-tide events. This is similar to findings from the UK (Haigh et al., 2016), despite NZ having smaller tides. Extreme events more commonly impacted the east coast of the North Island of NZ during blocking weather types, and the South Island and west coast of the North Island during trough weather types. The seasonal distribution of both extreme storm-tide and skew-surge events closely follows the seasonal pattern of mean sea-level anomaly (MSLA) – MSLA was positive in 92 % of all extreme storm-tide events and in 88 % of all extreme skew-surge events. The strong influence of low-amplitude (−0.06 to 0.28 m) MSLA on the timing of extreme events shows that mean sea-level rise (SLR) of similarly small height will drive rapid increases in the frequency of presently rare extreme sea levels. These findings have important implications for flood management, emergency response and the insurance sector, because impacts and losses may be correlated in space and time.