From Virginia Tech something that makes you wonder about past storm intensity and the need to protect shorelines from storms coming from the sea. With all the hype surrounding “Superstorm Sandy”, it is interesting to see that 150 years ago, simple engineering made the storm less intense in this one area.
Long-forgotten seawall protected New Jersey homes from Hurricane Sandy’s powerful storm surges
Virginia Tech researchers say relic seawall came in handy for New Jersey town
Picture two residential beach communities on the New Jersey shore: Bay Head and Mantoloking, which sit side-by-side in Ocean County on a narrow barrier island that separates the Atlantic Ocean and Barnegat Bay.
Before Hurricane Sandy landed on Oct. 29, 2012, a motorist traveling north on Ocean Avenue would seamlessly travel through Mantoloking into Bay Head, noticing few changes in residential development, dunes, beaches, and shoreline.
The difference was hidden under the sand.
A forgotten, 1,260-meter seawall buried beneath the beach helped Bay Head weather Sandy’s record storm surges and large waves over multiple high tides, according to a team of engineers and geoscientists led by Jennifer L. Irish, an associate professor of civil and environmental engineering in the College of Engineering at Virginia Tech and an authority on storm surge, tsunami inundation, and erosion.
The stone structure dates back to 1882. Its reappearance surprised many area residents, underscoring the difficulties transient communities have in planning for future threats at their shores, the researchers said.
“It’s amazing that a seawall built nearly 150 years ago, naturally hidden under beach sands, and forgotten, should have a major positive effect under the conditions in which it was originally designed to perform,” said H. Richard Lane, program director in the National Science Foundation‘s (NSF) Division of Earth Sciences, which funded the research. “This finding should have major implications for planning, as sea level rises and storms increase in intensity in response to global warming.”
The discovery, now online in the journal Coastal Engineering and slated for the October print edition, illustrates the need for multi-levels of beach protection in oceanfront communities, the researchers said.
“Once we got there, we immediately saw the seawall,” Irish said. “The beach and dunes did their job to a certain point, then, the seawall took over, providing significant dampening of the waves. It was the difference between houses that were flooded in Bay Head and houses that were reduced to piles of rubble in Mantoloking.”
With recovery efforts under way and storms still circulating through the area, Irish and Robert Weiss, an assistant professor of geosciences in the College of Science at Virginia Tech, with Patrick Lynett, an associate professor of civil and environmental engineering at the University of Southern California, documented high water marks, damage, overwash, and breaches of the barrier island.
All oceanfront homes in the two boroughs were damaged, ranging from ground-floor flooding to complete destruction. As measured by water lines on the interior of homes, flooding was similar in both boroughs. The difference was the extent of the storm’s impact.
In Mantoloking, the entire dune almost vanished. Water washed over the barrier spit and opened three breaches of 165 meters, 59 meters, and 35 meters, where the land was swept away. In Bay Head, only the portion of the dune located seaward of the seawall was eroded and the section of dune behind the seawall received only minor local scouring.
Later, using Google Earth to evaluate aerial images taken two years before and immediately after Hurricane Sandy, the research team evaluated houses, labeling a structure with a different roofline as damaged, one that no longer sits on its foundation as destroyed, and the remaining houses as flooded.
The researchers classified 88 percent of the oceanfront homes in Bay Head as flooded, with just one oceanfront home destroyed. In Mantoloking, more than half of the oceanfront homes were classified as damaged or destroyed.
Despite the immense magnitude and duration of the storm, a relatively small coastal obstacle reduced potential wave loads by a factor of two and was the difference between widespread destruction and minor structural impacts, the researchers said.
“We have a great deal of compassion for the people who have had to endure the devastation of Hurricane Sandy in Bay Head and Mantoloking,” Irish said. “It will have little solace, but we are left with a clear, unintentional example of the need for multiple levels of defense that include hard structures and beach nourishment to protect coastal communities.”
This research was supported by the National Science Foundation via grant EAR-1312813.
If someone tried to build a little seawall like that now, you’d have homeowners demanding something big enough to not just protect their properties from destruction but flooding as well.
Once the politicians had buckled under to that idea, then the environmentalists would come in and start banging their kitchenware, and nothing would get built for a quarter-century if ever.
Well, yes good engineering was and is a solution to protect against natural disasters. Question is if they are left to build that and the fundings are available…
Does anybody know, would the Katrina New Orleans’ disaster have been avoided if the initial design would have been followed?
“Hurricane Betsy in 1965 alerted a new generation to the threat of major hurricane hits. As radar showed the storm heading for the city, a mandatory evacuation of Eastern New Orleans was declared. The Mississippi River-Gulf Outlet Canal channeled storm surge into the metro area.[citation needed] A levee failure was responsible for major flooding in Lower 9th Ward.
The heavy flooding caused by Hurricane Betsy brought concerns regarding flooding from hurricanes to the forefront. Betsy resulted in major redesign of levee system. By authorizing the United States Army Corps of Engineers to design and construct the flood protection, Congress essentially overrode responsibility for the local flood protection by the local levee boards. The Flood Control Act of 1965 directed the Corps of Engineers to design and construct the flood protection for the maximum anticipated hurricane for the area. (This project was still under construction when the city was hit by Katrina 40 years later.)
The Corps of Engineers also designed a Lake Pontchartrain Hurricane Barrier to shield the city with flood gates like those that protect the Netherlands from the North Sea. Congress provided funding and construction began in 1971, but work stopped in 1977 when a federal judge ruled, in a suit brought by the environmental group Save Our Wetlands, that the Corps’ environmental impact statement was deficient. In 1985, after nearly a decade of court battles, the Corps scrapped the plan, and decided on reinforcing the city’s levee system instead.”
https://en.wikipedia.org/wiki/Hurricane_preparedness_for_New_Orleans
Solving problems posed by nature rather than accessing gravy train funding is a forgotten art.