WILMINGTON, Del. -- The man in charge of safeguarding Delaware's ocean coast parked along Del. 1 as a big storm raged. He got out of his vehicle, waded through thigh-deep water and climbed to the top of a dune.
There, he saw something he never expected.
"I watched entire dunes gone in one wave," said Anthony P. Pratt, Delaware's shoreline and waterway administrator. "I never would have guessed that one wave or two waves could have done that. ... It would be like pouring water on a pile of sugar."
Even during the pounding of ordinary nor'easters, sand spreads out and flattens. Protective dunes disappear.
A newly released U.S. Geological Survey report suggests that dunes along much of the mid-Atlantic coast, including Delaware, are vulnerable to extreme erosion in a Category 1 hurricane -- but big enough to take a direct hit without exposing the land behind to flooding.
But data for the USGS survey was collected before superstorm Sandy savaged beaches up and down the Eastern Seaboard, making the report's kilometer-by-kilometer survey of erosion vulnerability subject to wide variations. Under the pre-Sandy scenario, Delaware appeared to be in a better position than its neighbors -- certain to lose much of any beach in the next big storm but less likely to see inland areas flooded or buried by sandy overwash.
Yet as the Army Corps of Engineers figures out how and where to place 26 million cubic yards of sand to repair defenses of the Eastern Seaboard, some communities are exposed during this year's "extremely active" hurricane season. Federal weather experts have predicted 13 to 20 named tropical storms this year, with up to 11 becoming hurricanes and as many as six reaching major storm status with winds of 111 mph or more.
Along the East Coast, some beach renourishment projects are months, or years, away. In Delaware, all renourishment is tentatively scheduled to begin this year or in late spring 2014.
Unexpected Delaware trouble spots are in places where there are high dunes next to low ones, places such as Herring Point at Cape Henlopen State Park. Waves wash over low spots and inundate land far beyond the beach.
Clearly, though, Delaware's most vulnerable beach is the Indian River Inlet, where Sandy flattened a 15-foot-high dune. Federal researchers estimated that waves in a Category 1 storm would reach nearly that same 15-foot level and would rise to 29 feet in a Category 4 storm.
The Corps recently awarded a $6.6 million contract to a Seattle firm to build a milelong, 16-foot high dune north of the inlet.
"Global warming is a very serious problem, and some people are totally oblivious to that fact," said Alicia Falzon, who has lived in an oceanfront home in the Gulls Nest, Del., community north of Bethany Beach for nearly two decades.
Falzon said her home has never seen serious damage from a storm, despite frequent flooding and storm losses in nearby Bethany Beach and South Bethany. Yet dunes in her neighborhood are only about 1 foot higher than predicted waves in a Category 1 hurricane. In a Category 2 storm, waves would come in a full yard higher than dune tops, according to the geological survey analysis.
Last week, a report from the World Meteorological Organization warned of more frequent and more severe storms in coming decades as global warming triggers climate changes and higher sea levels. That warning followed a recent Massachusetts Institute of Technology study explaining that "100-year storms," often equated with Category 1 hurricanes, will happen every three to 20 years by the last two decades of this century as greenhouse gas emissions trap more heat in the atmosphere.
Storms will become more powerful, and big storms will arrive more frequently.
So-called 500-year storms could hit as often as four times a century, MIT concluded.
Skip Stiles, who directs the Virginia-based national group Wetlands Watch, described the USGS survey as a good start but noted planners need to change their approach and look ahead quickly.
"All of these studies are based on data sets from the past to the present. They're static, retrospective," said Stiles, whose group focuses on wetland, dredging and erosion issues. "As we're becoming increasingly aware, that no longer works with sea-level rise. We need to evaluate how long protection lasts before we have to talk about other measures."
Rising waters and powerful storms will challenge taxpayers' willingness to continually pay for storm damage and to dredge sand offshore and pump it onto beaches. Sandy prompted Congress to approve more than $60 billion in storm aid.
"There may come a point some decade or decades down the road" when sea-level rise and ongoing costs force officials to reconsider, said Jeffrey Gebert, coastal planning chief for the U.S. Army Corps of Engineers Philadelphia District.
"There may be some reason to rethink things, in particular whether the states want to stay on the path of continued, periodic (beach) nourishment," Gebert said. But that time may still be "a decade or decades down the road."
The USGS work examined current hurricane risks from the coast of Florida to North Carolina and from Virginia to New York, producing two reports and an interactive online map.
The documents provided a breakdown of three key vulnerabilities: damage from waves colliding with dunes; damage from overwash; and the worst, inundation, where dunes are washed away, the landscape is flattened and the area is flooded with seawater.
Although limited to average predictions for each 1-kilometer segment of beach, the study revealed serious weaknesses along the entire Atlantic seaboard. An earlier version for the Gulf Coast, released last year, found that a direct Category 1 strike probably would overwash 70% of Gulf shorelines. The Gulf Coast is among the most vulnerable in the nation because its dunes are so low.
Hilary Stockdon, lead researcher for the USGS effort, said the reports deal only with hurricanes and only with ocean shorelines. Bays and tidal rivers are not included.
Stockdon said the USGS report's profile of the shoreline depends on what's happening to the dunes.
"Where there is a low spot, there can be flooding behind the dune and interaction (flooding) with other areas down the beach that maybe weren't as vulnerable to begin with."
Stockdon, who is based at the USGS Coastal and Marine Science Center in St. Petersburg, Fla., said similar vulnerability assessments are in the works for nor'easters. Later work could account for the added vulnerabilities from sea-level rise and changes in dune and beach heights along the mid-Atlantic after Sandy.
Science of waves
Hurricane waves are typically different from waves that come with nor'easters.
A nor'easter wave may be big, but they come just a few seconds apart, about every 7-10 seconds. They chop away at the beach and dune, and once the storm passes, the dune forms a clifflike effect. Nor'easters do maximum damage if they linger through many high tide cycles.
A hurricane wave is big, with each one pounding the beach about 15-20 seconds apart. These are the sort of waves that Pratt witnessed wiping out dunes like they were piles of sugar. These waves have time to build pounding strength and energy, he said. They are so powerful, they have the might to run up over the dune and wash it away.
Once a hurricane becomes stronger, the storm surge takes over as the most damaging factor. Storm surge also plays a role in lower category hurricanes, but the waves are like the warm-up band at a rock concert, getting things pumped up for the headliner.
The idea, according to the USGS report, is that waves erode the beach and higher storm surge shifts the damaging waves higher onto the shoreline surface. Once that happens, waves can inundate areas, taking out roads and bridges and severing evacuation routes.
The report provides some examples:
• During Hurricane Ivan in 2004, a five-story condominium in Orange Beach, Ala., collapsed after the sand dune supporting the foundation eroded.
• Hurricane Sandy, which made landfall as an extra-tropical cyclone on Oct. 29, 2012, eroded and undermined beaches and dunes, and roads, boardwalks and foundations were destroyed or damaged in Seaside Heights, N.J.
• And then there was Mantolonking, N.J., where storm surge and waves from Sandy caused inundation and a new inlet to cut through an area that prior to Sandy had homes, businesses and a road.
Gebert, who was part of a group that developed new Corps of Engineers requirements to consider climate change in future building projects, said Sandy had strikingly different effects on communities with and without dunes. Beaches without dunes suffered far greater losses.
"It goes to show you that it really does work," Gebert said. "There certainly isn't any information from Sandy, not in Delaware and not in New Jersey, that would suggest any reason to alter the course."
Jeff Montgomery and Molly Murray, The (Wilmington, Del.) News Journal