The influence of future weather pattern changes and projected sea-level rise on coastal flood impacts around the UK

When local extreme water levels surpass defences, the consequences can be devastating. We assess the importance of sea-level rise and future weather pattern changes on UK coastal flood impacts. Historical weather pattern classifications are matched with the observed skew surges and significant wave heights. Coastal-risk weather patterns are then defined as >= 1% of events in the distribution exceeding the local warning threshold. We combine this methodology with projections of sea-level rise and weather pattern frequency occurrences, to determine the relative importance of each on future coastal risk. A deep low-pressure system situated to the west of Ireland (WP29) has the highest probability (6.3%) of exceeding Newlyn's present-day warning threshold; this is projected to increase under climate change to 46.2% by 2050 under RCP2.6. This work found that weather patterns associated with storm surges are increasing and decreasing in frequency; a synoptic situation causing windy conditions in the north of the UK (WP23) will increase by > 40% under RCP8.5 by the end of the century (2079-2090). When combining the impact of sea-level rise and changing frequency of weather patterns, this study found that sea-level rise dominates future coastal risk and is highly linked to the future emission scenarios. The need for successful adaptation, such as coastal defence improvements and early warning systems, will become even more important under the higher emission pathway. The most significant increases in coastal risk are found along the east coast, through the English Channel to the north Devon coastline.