In 1900, coastal communities could expect certain extreme water level events to occur on average once in a century; in other words there was only a 1% chance to experience such an event in any given year. Now, the same extreme water level is expected about once every eight years, on average, due to the increase in sea level.
A new study published in Nature Climate Change co-authored by Associate Professor of Civil, Environmental and Construction Engineering Thomas Wahl shows that historically rare coastal water level extremes that were expected to occur on average only once in 100 years are now 12 times more likely to occur. This is the average across all coastal locations, in some regions what used to be a 1-in-100-year event is now expected annually.
鈥淚f you live within FEMA鈥檚 100-year flood zone, you have a 100-sided die that you roll every year,鈥� says Wahl, a College of Engineering and Computer Science researcher and UCF Coastal faculty cluster initiative member. 鈥淪o you have 99 chances of being fine and one chance of being impacted by storm surge. Now, because of sea level rise, that die is losing sides and at some point there are so few sides left that it becomes a risk that not everybody may be willing to take going forward.鈥�
The catalyst for increased coastal water level extremes and associated flooding is sea level rise, which has increased globally by nearly eight inches over the past 126 years. Using various observational data sets and leveraging model simulations, Wahl and his research collaborators were able to distinguish the various factors that cause sea level rise. Although natural variability is still a large factor, anthropogenic forcing is now the primary cause.
鈥淲e leveraged tide gauge and satellite observations along with existing model outputs to distinguish between the part of sea level rise that could easily be natural variability 鈥� the ups and downs we鈥檝e experienced for hundreds of thousands of years 鈥� and the part that cannot be explained by natural variability,鈥� Wahl says. 鈥淎nd we found that anthropogenic forcing alone leads to a four-fold increase in this likelihood of a one-in-a-100-year event to occur, and it鈥檚 now the main driver of the increased likelihood of these extreme water levels to occur.鈥�
Recently, Wahl also contributed to a study published in Nature Geosciences that reveals that sinking ground levels and rising sea levels are occurring more rapidly than previously understood, often worsening flooding in coastal communities. These combined findings a need to reassess coastal infrastructure and flood-planning efforts as past flood frequency estimates may no longer represent modern-day conditions.
Wahl collaborated on this study with researchers from Tulane 海角直播, Harvard 海角直播 and various academic and research institutions in both Germany and the Netherlands. Prior to joining UCF in 2017, Wahl was a Marie Sklodowska Curie Fellow of the European Union at the 海角直播 of Southampton and a postdoctoral scholar at the 海角直播 of South Florida. His research spans the areas of coastal flood risk, sea level rise and storm surges.
