Severe floods, which typically occur only once in a century, may become an annual threat to coastal communities by the end of the 21st century due to rising sea levels. A recent study reveals that even under a moderate scenario where carbon dioxide emissions peak by 2040, most coastal areas will face 100-year floods every year by the century’s close. Moreover, as early as 2050, regions worldwide could encounter 100-year floods every nine to fifteen years on average.
Historically, a 100-year flood is defined as an extreme water level with a 1% chance of occurring in any given year. However, it is essential to note that despite the name, these floods can strike an area in consecutive years or not at all within a century. The study indicates that this historical perspective will no longer accurately predict future flood occurrences.
Hamed Moftakhari, a civil engineer and professor at the University of Alabama overseeing the project, emphasizes that in a warmer climate, the threshold for a 100-year flood will be surpassed far more frequently, rendering them no longer rare events. This research was recently published in Earth’s Future, AGU’s journal dedicated to interdisciplinary research concerning the Earth and its inhabitants’ past, present, and future.
This study primarily focuses on sea level rise as a significant contributor to long-term flooding rather than immediate storm-driven inundation. As sea levels rise, coastal infrastructure becomes increasingly vulnerable to the impacts of storms, tides, and waves, heightening the risk for coastal communities.
To conduct their analysis, researchers utilized data from over 300 tide gauges worldwide, considering two carbon emission scenarios outlined by the International Panel on Climate Change: one where carbon dioxide emissions continue to rise throughout the century and another where emissions peak by 2040 and then decline. In both scenarios, the study indicates that sea level rise will lead to an increase in 100-year flood events in most of the studied locations.
To mitigate the impending flooding risks and avoid disasters, Moftakhari suggests adopting a proactive approach to land planning, urban development, and coastal protection measures. Realistic forecasts of future coastal conditions are a crucial starting point.
Traditionally, engineers designing structures such as sea dikes, seawalls, and breakwaters relied on the concept of stationarity to predict future water levels. Stationarity assumes that past patterns will remain unchanged in the future. However, under climate change, various factors are altering these patterns, making stationarity an unreliable assumption for coastal flooding predictions.
Moftakhari emphasizes the need to update tools, design guidelines, and practices to account for the changing nature of coastal floods. More than 600 million people reside in low-lying coastal regions, a number expected to rise, and well-designed coastal defenses are essential to withstand increased flooding.
As sea levels continue to rise due to warmer ocean temperatures and glacial meltwater, accurate estimates of future flood risk are crucial. Different regions will experience unique challenges and require customized solutions based on local conditions. Moftakhari remains optimistic, emphasizing that disasters result from human decision-making, and technological advancements can enhance community resilience in the face of rising seas.
In conclusion, the study underscores the urgent need for coastal communities to adapt to the changing landscape and increase their resilience to the growing threat of recurrent extreme floods.