Rising seas threaten Delaware coastal areas

• The UN recently estimated that sea levels globally will increase by up to 3.2 feet by 2100
• The "Mother%27s Day" storm of 2008 caught many residents by surprise

Along Prime Hook Beach, one of Delaware's most flood-threatened spots, longtime resident James A. Joyce Jr. said he pays attention to hurricane hazards, but worries more often about winter northeast storms.

"I've been here 18 years now and we've been fortunate so far," Joyce said. "None of the hurricanes have really hit us hard. But hurricanes are always bad for somebody, and eventually our luck is going to run out."

For Delaware's coastal residents, all storms – be it a fast moving but highly destructive hurricane or the slow, incessant pounding of a nor'easter – spell flooding and erosion at the least and property damage at the worst.

And with sea level rise, the impact from storms stand only to get worse, said Susan Love, a Delaware Coastal Programs manager.

"Sea level rise closes our margin of safety when we have these events," she said. "The risk is increasing."

Sea level at Lewes Breakwater Harbor has risen a foot over the last century and is expected to continue to increase at an accelerating rate as global warming expands oceans and melts polar ice, glaciers and frozen land masses.

Although Love said that coastal residents could once breath a sigh of relief if the worst of a storm hit at low tide, "the window is closing on that opportunity," she said.

The United Nations Intergovernmental Panel of Climate Change recently estimated that sea levels globally will increase by about 1.7 to 3.2 feet by the end of the century. Related research forecasts note that mid-Atlantic increases could reach 1.7 feet by 2050 and 3.2 to 4.9 feet by 2100 because of local geologic factors.

With a 1.7-foot addition to hourly water levels over the past 12 months, Lewes would have experienced seven days with high tides exceeding those seen during Hurricane Irene in August 2011, the eighth highest ever recorded for the state's oldest tide station. And using that same mid-century projection, Superstorm Sandy's highest tide at Lewes, on Oct. 29, 2012, would have been more than a foot higher than the highest water level during the March 6, 1962, northeast storm that has long ranked as Delaware's worst.

Adding the 3.2 foot end-of-century rise projected for Delaware to the last 12 months of hourly water levels recorded at Lewes would mean 16 days with high tides exceeding the March 1962 all-time record at Lewes, and 49 days with water topping levels hit during Superstorm Sandy at the same spot. That scenario includes seven consecutive days in mid-October 2013 that would have had tides higher than Sandy's worst.

In fact, all of the other top 10 storms recorded at Lewes would have exceeded the '62 storm if mid-century sea level rise forecasts were part of the picture. If levels rise by the 4.9-foot total projected in grimmer scenarios, in 2100 the highest tide at Lewes every day, on average, would exceed the '62 storm by nearly 5 inches, with storms and waves adding more feet and sending water deeper inland than the worst storms to date.

While residents can do little to turn away storms, those in harm's way can count on earlier warnings about extreme weather, and better information about the scale of the threat.

"When it comes to hurricanes and tropical systems, we have gotten better at forecasting where they're going to impact land," said Daniel Leathers, a University of Delaware professor and Delaware's state climatologist. "Hurricane Sandy is an excellent example. It was very well forecast."

In the seven short years since the "Mother's Day" storm of May 2008 caught hundreds of coastal community residents in their beds, warning systems have improved at every level. They range from online, minute-by-minute forecasts of storm surges and high-tide timings and water levels on roads to old-fashioned commitments to door-knocking.

High on the list is the Delaware Bay Coastal Flood Monitoring System, a collaboration by University of Delaware scientists that provides weather, current tide conditions and elaborate flood forecast maps from New Castle to Lewes.

Similar, but less-focused tide storm surge prediction centers include New York's Stony Brook Storm Surge site, the Extra-Tropical Storm Surge forecast center operated by the National Weather Service, as well as the same agency's Ocean Prediction Center, which provides hour-by-hour, coastwide guidance on high-water timing.

The new tools give community and emergency management leaders and residents extra hours and days to prepare, Leathers said.

In Kitts Hummock, longtime resident Michael Costello said the multiplying warning systems are welcome additions to life on the bay.

"All the residents here, many of whom were here during the '08 storm, have changed their perspective," Costello said. "We know and monitor the weather. We prepare and when we see or hear something, we tell each other."

"The most-impressive thing is the county and Little Creek Volunteer Fire Company. We have reverse 911 calls if there's an alert, and the fire company volunteers will come out a day or two before a storm is supposed to hit," Costello said. "They're phenomenal. They knock on our doors, give us flyers, ask if we're prepared and know where the evacuation center is."

That storm did catch many Delaware Bay residents by surprise and it showed a weakness in the system, Love said.

The forecast for the storm didn't show much of a storm surge for Lewes or Wilmington, she said. But the storm had a huge tidal surge impact in the the rest of the Delaware Bay and River, she said.

It convinced folks that better data was needed for the Delaware Bay and resulted in the coastal flood monitoring system, she said.

Love said planners learned a similar lesson from Superstorm Sandy in 2012. The storm did little lasting damage along the ocean coast of Delaware except at the highly vulnerable Indian River Inlet Bridge.

But along the inland bays – Rehoboth, Indian River and Little Assawoman – it caused a storm surge and flooding that was among the highest levels on record. Love said they hope to have a similar monitoring system in place for the bays.

Meanwhile, the National Weather Service is trying out a new potential flood and storm surge map that will be up and running as hurricanes move landward.

Holly Bamford, director of the NOAA Ocean Service said the map is an experimental tools that will allow communities and planners to make decisions quickly based on the best available information on tides, currents and water levels that are plugged into a storm surge model.

"Storm surge can be seriously deadly," she said. "It only takes 6 inches of fast moving water to knock an adult over."

But mostly, she said, people in vulnerable coastal areas need to tools to be better prepared and more resilient.

Reach Jeff Montgomery at 463-3344 or jmontgomery@delawareonline.com. Reach Molly Murray at 463-3334 or mmurray@delawareonline.com. Follow her on Twitter @MollyMurraytnj.