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New research anticipates rise in nuisance flooding in coastal communities

University of Delaware/Delaware Sea Grant

For most people, nuisance flooding is just an inconvenience -- like when a roadway floods in heavy rain. But as sea levels rise, this kind of flooding is happening more often.

As Delaware Public Media's Eli Chen reports, new research says it could continue escalating in coastal areas like Delaware's.

Driving is a crucial part of Aaron Mifflin’s job as a cable installer for Comcast. But getting around Delaware’s coastal neighborhoods sometimes isn’t easy. Mifflin says beachside roads, like Cedar Street in Lewes, has proved to be a navigational challenge when it floods.


“There’s no side streets to go around it, so you either have to cancel the job or wait for it to go down or go through it, if you can go through it,” said Mifflin.

And it’s not just annoying. Mifflin has lived nearby in the town of Milton for 34 years -- his whole life -- and he says the flooding is bad for local businesses.

"Yeah, a lot of businesses," Mifflin said. "A lot of businesses got ruined.”


And he says he’s seeing more water on the roads lately than he’s ever before. Mifflin’s observations of more flooding on the streets, which is sometimes called nuisance or sunny day flooding, is on par with the trends that scientists are seeing in coastal communities.

Decades ago, it used to be that you needed a pretty big storm to cause nuisance flooding. But now, a high tide can be all it takes to see it in Delaware and many other coastal areas,  thanks to combination of sea level rise and sinking land mass.

According to the National Oceanic andAtmospheric Administration, which uses records from a tide gauge in Lewes, the average number of nuisance flooding days a year was about five days in the early 1960s. Fifty years later, that number has increased by 300 percent - to an average of 22 days a year.


“We are experiencing frequent tidal flooding in the state of Delaware and we could expect to see more of the same and deeper flooding in the future,” said Susan Love, the head of DNREC’s Climate and Sustainability Section.

In September, NOAA reported that some mid-Atlantic communities could see a record number of nuisance flooding days this year due El Nino patterns--which sends strong northeasterly winds in our region. In the report, NOAA said Lewes could expect 41 nuisance flooding days this year.

“That is quite a lot of days during the year where you’ll see nuisance flooding, where you’ll see a lot of water standing on roads,” Love said.

And looking into the future, scientists recently published a study in the journal Geophysical Research Letters that looks at how sea level rise will affect nuisance flooding on the Eastern seaboard by 2050.


“With the expected projections, nuisance flooding will increase almost everywhere,” said study co-author Amir AghaKouchak, a hydrologist at the University of California-Irvine.

That increase will vary widely, between about 10 percent and 270 percent, according to the study. Cities further inland, like Philadelphia, will experience a relatively small increase. Others, like Atlantic City, can expect more days of inconvenient flooding a year.

AghaKouchak says on average, the current rate at which seas are rising should increase 80 percent by 2050. That'll result in a 55 percent increase in nuisance flooding events. Because of what the data shows, he believes that coastal communities need to strongly consider the social, economic and health impacts of increased flooding.  

“We need different groups of people, communities, stakeholders to think about these projections and come up with ideas for adaptation, mitigation and better planning to reduce our risk,” said AghaKouchak.

These kinds of stakeholder meetings and discussions have already started taking place in Delaware. Gov. Jack Markell’s Executive Order 41 also requires all state agencies to prepare the state for future effects of climate change.

Jim Pappas, DelDOT’s assistant director of performance management, says planning long-term for an increasingly flooded future is a major priority for the agency.


“There are going to be changes and we need to adapt very quickly,” said Pappas.

But making roads more resilient, less floodprone is a challenge. Pappas says one obvious way is to elevate roads. But that doesn’t work everywhere--especially, say marshy areas along route 9.

“If we add height to the road, if we keep adding more pavement, it literally keeps sinking because the marsh underneath there is very soft and spongy," said Pappas. "So if you put more weight on top, --because it’s not a firm base--it will cause the pavement to sink over time.”

And another way is to improve the road’s drainage system. Right now, DelDOT’s able to use cameras to identify problematic roads. And they can replace or fix clogged pipes to make sure the water runs off the road. But Pappas adds that this type of short-term solution isn’t effective in tidal areas.

“Especially in Sussex County, there’s no place to run the water," said Pappas. "That’s where the bigger challenge comes in, working the design programs to say, hey we need to raise the road or work with DNREC to create wetlands and things like that. More innovative, kind of out of the box thinking.”

And using the local ecology, like building marshes and wetlands, could play a huge role in sustaining Delaware’s transportation system. However, Pappas notes that lack of funding poses a major obstacle in executing these innovative, out of the box solutions.

So exactly how much nuisance flooding Delawareans can expect in the coming decades could change over time, as scientists like Amir AghaKouchak continue to analyze climate and emissions data. But even as the projections fluctuate, experts all agree that flooding will only go up.

Aaron Mifflin, from Milton, knows that beyond having to circumvent flooded streets sometimes, sea level rise is making it harder to afford coastal living.  

“You got to have a lot of money to live down here, near the water. The insurance is very expensive,” said Mifflin.

And the data shows sea level rise will continue to make life in Delaware more difficult. The future for residents like Mifflin depends not only on what the scientists’ projections can tell us, but most importantly, what the community decides to do because of them.

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