The University of New Hampshire scientists found that high tide floods, or so-called 'nuisance flooding,' that happen along shore roadways during seasonal high tides or minor wind events along the US East Coast are occurring far more frequently than ever before. Turning words to numbers, these scientists found that in the past 20 years roads along the East Coast have experienced a 90 percent increase in flooding – often making the roads in these communities impassable, causing delays, as well as stress, and impacting transportation of goods and services.
"This could be just the beginning of impact on these areas," said Jennifer Jacobs, professor of civil and environmental engineering. "With the continued rise in sea levels, the nuisance-flood frequency is projected to grow and the effect on the physical roads and the people that live along the coastline is concerning."
The researchers found that tidal nuisance flooding threatens over 12 000 km (7 500 miles) of roadways along the entire East Coast, with over 400 miles of that being interstate roads.
They estimate that this causes over 100 million hours of delays each year for drivers on those roads and that number could rise to more than 3.4 billion hours by 2100. By the middle of the century (2056 –2065), they predict nuisance flooding could occur almost daily at specific sites along the shores of Connecticut, New Jersey, Maryland, the District of Columbia, North Carolina, and Florida under an intermediate sea-level-rise scenario.
"As tidal coastal flooding increases in the coming years, there will also be issues with the transportation infrastructure," said Jacobs. "We’ve already seen billions of dollars in damage to coastal roadways from recent hurricanes. In the future, with rising sea levels, we expect to see more frequent issues, more damage, and impact to roadways even farther inland."
Researchers note that these impacts are not limited to storm events. They say that critical transportation infrastructure is at risk from sea level rise alone; which numerous transportation agencies project to be between 0.3 - 2.4 m (1 - 8 feet), along the U.S. Atlantic and Gulf Coasts.
Vulnerable roads were identified using data from the Federal Highway Administration’s Highway Performance Monitoring System and National Oceanic and Atmospheric Administration’s Center for Operational Oceanographic Products and Services. They looked at flood frequency maps, tidal gauge historic observations, and future projections of annual minor tidal flood frequencies and durations.
"Recent and Future Outlooks for Nuisance Flooding Impacts on Roadways on the US East Coast" - Jennifer M. Jacobs et al. - March 13, 2018 - Transportation Research Record - https://doi.org/10.1177/0361198118756366
Tidal floods (i.e., “nuisance” flooding) are occurring more often during seasonal high tides or minor wind events, and the frequency is expected to increase dramatically in the coming decades. During these flood events, coastal communities’ roads are often impassable or difficult to pass, thus impacting routine transport needs. This study identifies vulnerable roads and quantifies the risk from nuisance flooding in the Eastern United States by combining public road information from the Federal Highway Administration’s Highway Performance Monitoring System with flood frequency maps, tidal gauge historic observations, and future projections of annual minor tidal flood frequencies and durations. The results indicate that tidal nuisance flooding across the East Coast threatens 7508 miles (12,083 km) of roadways including over 400 miles (644 km) of interstate roadways. From 1996–2005 to 2006–2015, there was a 90% average increase in nuisance floods. With sea level rise, nuisance-flood frequency is projected to grow at all locations assessed. The total induced vehicle-hours of delay due to nuisance flooding currently exceed 100 million hours annually. Nearly 160 million vehicle-hours of delay across the East Coast by 2020 (85% increase from 2010); 1.2 billion vehicle-hours by 2060 (126% increase from 2010); and 3.4 billion vehicle-hours by 2100 (392% increase from 2010) are projected under an intermediate low sea-level-rise scenario. By 2056–2065, nuisance flooding could occur almost daily at sites in Connecticut, New Jersey, Maryland, the District of Columbia, North Carolina, and Florida under an intermediate sea-level-rise scenario.
Featured image: Driver ventures down flooded road made impassable by coastal flooding in Rye, N.H. Credit: Kim Reed, UNH