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Learning the recipe for high-tide floods

Learning the recipe for high-tide floods

NASA funds ambitious research of extreme sea-level events

By Daniel Hentz | October 13, 2020

A new WHOI-led research initiative will receive $1.5 million from NASA to investigate the role of various processes behind extreme sea-level events that lead to coastal high-tide flooding around the world.

Close to 40% of Americans live in coastal counties. In cities like Boston, Miami, and Norfolk, many have experienced the negative effects of high-tide flooding, from closed streets to ruined foundations and coastal erosion. Along the U.S. Atlantic and Gulf coasts, some communities now experience this type of flooding 100% or even 1000% more frequently than they did just 20 years ago, according to a recent report by NOAA.

Yet, while scientists agree that sea level rise will lead to more frequent high-tide flooding, many want to understand in greater detail what role local, regional, and global environmental factors play in driving the underlying extreme sea levels causing these events.

“The frequency of high-tide flooding events occurring around the U.S. and worldwide is rapidly accelerating,” says WHOI physical oceanographer Chris Piecuch. “When you’re down by the water, that sea level that you feel is actually the compounding effect of multiple things,”—things like land subsidence, shifts to nearby currents, changes in the tides, and proneness to storms.

The new NASA-funded, four-year project intends to look more closely at this recipe of environmental conditions and their influence over sea level in the next 30 years. The team, led by Piecuch, and consisting of six other co-investigators from four scientific institutions, will leverage data from NASA satellites and a network of NOAA tidal gauges for information. The combined datasets will give researchers the ability to tease out the influence of other factors, beyond the increase in ocean volume from global melting of land ice.

“We’re trying to have an understanding of the past, but also looking to the future (the next few decades), how these different ongoing processes are relatively contributing to high sea levels, and whether they confer any sense of predictability,” adds Piecuch.

High-tide floods usually occur over a matter of hours to days. Traditionally, such events can be observed by NOAA tidal gauges, which make on-the-minute measurements of coastal sea level. But these devices have their limitations. Tidal gauges only provide local information, and they're only found in some coastal cities and harbors. Thus, the extent and cause of any given high-tide flood—whether local or regional—can be unclear. That's where NASA satellites come in.

Sea-level satellites orbiting the planet every 10 days can generate a global snapshot of the state of sea level over the entire ocean. That's much-needed context for interpreting the available tidal-gauge data, adds Piecuch.

This WHOI-led project is one part of a larger, NASA-led effort, called Sea Level Change Team (NSLCT). This umbrella program, which began in 2014, employs the expertise of seven total teams, including more than 70 co-investigators spanning dozens of U.S.-based institutions. Each will look at different facets of sea level rise, from the short-term extremes studied by Piecuch’s team, to the more long-term evolution of glaciers and ice sheets.

In addition to furthering the science, NASA leadership has said this new program will focus primarily on producing practical models that stakeholders and city planners can use to prepare for the extreme sea-level events.

“We’re more interested in providing useful sea level information,” says Ben Hamlington, the NSLCT project coordinator at NASA’s Jet Propulsion Lab. “So it’s not just pushing the science forward, but providing guidance that’s useful to decision-makers and coastal communities.” 

Christopher Piecuch is a physical oceanographer who has spent 10 years studying the processes behind sea level change. (Photo by Daniel Hentz, © Woods Hole Oceanographic Institution)
Christopher Piecuch is a physical oceanographer who has spent 10 years studying the processes behind sea level change. (Photo by Daniel Hentz, © Woods Hole Oceanographic Institution)

For the NSLCT teams, that means identifying which domino could make an area more flood prone. Information like that, Hamlington says, will ultimately help policymakers navigate through the right strategies for their communities, from infrastructure repair to creating new storm evacuation routes.

“In terms of impacts to the coast, extreme events are really impacting these coastal communities now," says Hamlington. “This is definitely moving the needle in terms of what we can do with sea level science and how scientists can better meet the needs of a decision-maker or planner.”


Learn more about the nuances of sea level change in our report, "Understanding Sea Level Rise," available for free download.