By Karen Savage
High tide flooding, also known as sunny day flooding, reached or tied record levels in 19 U.S. locations last year, according to a report released earlier this month by the National Oceanic and Atmospheric Administration (NOAA). The report also projected this type of flooding will increase as the climate continues to warm, which underscores the efforts of the coastal communities that are trying to hold the fossil fuel industry financially accountable for its role in climate damages.
The NOAA report is the sixth in an annual series that examines high tide flooding, which can inundate streets and infrastructure even in the absence of storms. Using data from NOAA tide gauges—data most frequently used to make sure ships weighed down with cargo don’t run aground—the report spotlights the growing impact of rising sea levels to help communities prepare for future flooding.
“As this flooding occurs more often, communities need to know how to prepare to respond, what kind of resources might they need,” said William Sweet, a NOAA oceanographer and report co-author.
Because mitigation measures are specific to each community, the report doesn’t recommend any courses of action, nor does it mention how municipalities will pay for it all.
Many communities battling high tide flooding have turned to suing the fossil fuel industry to recover those costs. Those include Baltimore, New York, Washington D.C. and parts of Massachusetts and Rhode Island, which have each experienced a record number of days with high tide flooding since 2017.
Perhaps most alarming is that in many locations, particularly on the East and Gulf coasts, the number of days is increasing at an accelerated rate.
“The U.S. annual [high tide flooding] frequency now is more than twice that in the year 2000 due to rising relative sea levels,” Sweet and his co-authors wrote in the report.
Using data from the tide gauges, coupled with projected sea level rise data from the Fourth National Climate Assessment, the team predicted the number of high tide flooding likely to occur by 2030 and 2050.
“This gives a range likely over the next couple of decades that communities are likely to face, so that they can be prepared and have some sort of idea as to what the future holds, so they can determine when best to either to keep responding on the annual basis or try to get ahead of the curve per say and do some longer term corrective fixes,” Sweet said.
In many places, those projections are bleak.
Washington D.C., which last month filed a climate fraud lawsuit against ExxonMobil, BP, Chevron, and Shell, had three days of high tide flooding in 2000. The district experienced 10 such days in 2019 and that number is projected to reach 20 by 2030 and 120 by 2050.
Similarly, Baltimore had three days of high tide flooding in 2000 and 11 days in 2020. The city could reach between 15 and 25 days by 2030 and between 50 and 155 by 2050. The city filed suit in 2018 against ExxonMobil, Chevron, Shell and 23 other fossil fuel producers and distributors, alleging they knew for decades that fossil fuels drive climate change but deliberately failed to inform the public about those risks.
Providence, which had only three days of high tide flooding in 2000, is expected to experience 15 to 30 days by 2030 and between 40 and 105 days by 2050. Rhode Island became the first state to file a climate liability lawsuit against major fossil fuel companies in 2018.
In New York City, the number of days with high tide flooding has doubled from 5 in 2000 to 10 in 2019. That number could grow to between 20 and 40 days in 2030 and between 50 and 135 days by 2050. New York has appealed the dismissal of a climate liability suit it filed against BP, ConocoPhillips, Chevron, ExxonMobil and Royal Dutch Shell.
To the south, Sandy Hook, New Jersey could reach 160 days of high tide flooding by 2050 and Atlantic City could be in for up to 155 days. Legislators in that state are urging Governor Phil Murphy and Attorney General Gurbir S. Grewal to file suit against many of the same companies for climate-related damages.
West Coast locations are less affected by this kind of flooding, but still suffer impacts from rising seas and other climate impacts such as increased extreme weather events and storm surges. The report said that if no mitigation takes place and if the rate of carbon emissions stays the same, these impacts will worsen.
“Emissions do matter as we project towards the end of the century,” Sweet said, adding that while specific predictions beyond 2050 are uncertain, the trend is expected to continue.
“The assumption is that if flood defenses don’t change, your mitigation strategies don’t change, then the impacts will continue to mount,” Sweet said.
When high tide flooding occurs more than 180 days per year it crosses the threshold and becomes the new normal high tide. That will force communities to consider relocating coastal infrastructure and housing, incurring even higher costs.
“At some point it becomes an elevation game—lower elevations of the coasts will become more exposed and vulnerable to flooding than higher elevations, especially when it’s tidally-driven and less storm surge-driven,” Sweet said.
“The tide’s going to go where the tide wants to go.”