Tag Archives: Outer Banks

North Carolina’s mobile Outer Banks and its new, immovable Bonner Bridge

Cape Hatteras Lighthouse being moved

The Cape Hatteras Lighthouse being moved in 1999. Image from International Chimney Corporation website

The iconic Cape Hatteras lighthouse no longer sits on the ground on which it was built in 1870. Under threat from the encroaching sea, the 210 ft., 5,000 ton masonry structure was moved in 1999 about 2800 feet southwest from its original location. Masonry buildings, when shaken (during earthquakes, for example) tend to come apart along mortar lines, or even fall completely to pieces. So it isn’t easy to move them safely.

International Chimney Corp. of Buffalo NY and Expert House Movers of MD Inc., were awarded the moving contract. The job was carried out successfully; not a single brick was dislodged during the operation. The lighthouse is now about a third of a mile from tide water, distant enough, it’s hoped, to keep it safe from the sea until at least the end of this century. In recognition of the difficulties involved in moving the structure, the two company’s jointly won the American Society of Civil Engineers 40th Annual Outstanding Civil Engineering Achievement Award.

The following map shows the location of the lighthouse before it had to be moved:

Map showing shoreline recession at Cape Hatteras NC

History of shoreline recession at Cape Hatteras, Outer Banks, North Carolina (map also shows pre-1999 location of the lighthouse). Image: pubs.usgs.gov (paper 1177-B)

To visit the lighthouse up close, drive south from Bodie Island on Highway 12. The H. Bonner Bridge carries the road across Oregon Inlet, linking Hatteras Island to the northern Outer Banks. The economic life of Hatteras Island depends on it. By early next year, the new Bonner Bridge will be ready to take over from the old one.

Aerial photo ofOregon Inlet and old H.Bonner Bridge, Outer Banks NC

Oregon Inlet and the old H. Bonner Bridge. Photo taken from above Pamlico Sound looking east towards the Atlantic. Image: usgs.gov

Built in 1963 with a life expectancy of 30 years, the old Bonner bridge is in danger of falling down. The new bridge (due to open for traffic early next year) is built to last 100 years according to the designers, HDR Inc., an engineering company based in Omaha, Nebraska. The bridge is built on shifting sand, so that longevity claim is based on the company’s confidence in their engineering abilities. Domenic Coletti, HDR design manager, quoted in the company’s website, said this:

To our knowledge, no one has previously designed and built a [bridge] foundation where piles had to be jetted and driven through nearly 140 feet of soil [sand] in a way that still provided adequate capacity [stability] after 84 feet of scour occurs.”

SCOUR is the anticipated tearing away of the sand around the support piles due to ocean currents in the inlet.

Photo of the old and the new H. Bonner Bridges, Outer Banks, North Carolina

The old and the new H. Bonner Bridges crossing the Oregon Inlet, Outer Banks, North Carolina. Image from The Outer Banks Voice, 13/11/2018. Photo by Bob Moris

But consider this: although the new bridge may very well last 100 yeas, how many years will the inlet over which the bridge crosses remain in its present location?After all, storms have opened and closed numerous inlets along the Outer Banks since records began in the 16th century. A hurricane formed the Oregon Inlet in 1846. Another one could close it. The steady migration of the Outer Banks over time, may also cause problems. Here’s part of an October 16 email I sent to Pablo Hernandez, Resident Engineer, NCDOT, asking about that matter:

According to the US Geological Survey, the Outer Banks have historically migrated south at the rate of 60 to 70 feet per year, a process that sea level rise may speed up. This suggests that in 20 or 30 years, the Oregon Inlet may no longer be where it is now, thus leaving the new bridge without a function. I’m wondering what actions DOT plan to take to avoid such an outcome?”

No answer yet. My guess is that the Army Corps of Engineers will be kept busy dredging the channel for the indefinite future. What other solution is there? Unlike a lighthouse, a bridge can’t be moved. When Mr. Hernandez gets back to me I’ll update this post.

Map of North Carolina’s Outer Banks

Map of North Carolina’s Outer Banks showing location of Cape Hatteras lighthouse and Oregon Inlet. Image from U.S. National Parks Maps

North Carolina’s valuable pile of sand

This land isn’t permanent, it moves. This whole pile of sand moves with every storm with sea level rise, and it’ll continue to move for hundreds of years. And we’ve tried to engineer it like it’s Raleigh, like it’s a rock, but it’s not. It’s sand.” — Stanley Riggs, former professor of marine and coastal geography. — Courier-Tribune, Sept. 15, 2018

The pile of sand Riggs is talking about is the Outer Banks, the 200 mile string of barrier islands off the coast of North Carolina. His concern is the continuing development on that long sand bank, and the general lack of interest in restricting it.

Map of North Carolina’s Outer Banks

Map of North Carolina’s Outer Banks. Image from U.S. National Parks Maps

Given that the Outer Banks consist of shifting sands, sit barely above sea level, and are located in a part of the world subject to violent ocean storms, why is there continuing development?

The developers know that building houses and roads on sand is asking for trouble. The difficulties associated with the stability of buildings have been researched for well over 2000 years. Matthew, a great authority on the subject, said: ”And everyone who hears these words of mine and does not do them will be like a foolish man who built his house on the sand. And the rain fell, and the floods came, and the winds blew and beat against that house, and it fell, and Great was the fall of it.“ — The guy knew what he was talking about.

Image of fallen house on Hatteras Island, North Carolina

fallen house, Hatteras Island, Outer Banks, North Carolina. Image: Steve Early/ Virginia Post

North Carolina’s Coastal Resources Commission studied the situation in 2010 and wrote a report predicting a 39 inch rise in sea level by the year 2100, enough to flood coastal towns and wash away the existing built environment on the Outer Banks. Advocates for economic development in twenty of the State’s coastal counties formed the NC-20 group to lobby against the report which, they said, was based on bad science. It would, they argued, scare away business and tourists. The Legislature agreed, passed a bill prohibiting scary predictions, and ordered the commission to write something acceptable to the economic development people. The result was a 2015 report predicting a sea level rise of 6 – 8 inches by the year 2045. What a relief.

As well as the thousands of year-round residents and summer-cottage owners, the Outer Banks attract several million tourists each year. It’s a big enterprise and an important tax generator. Of course government wants to support it, and they’ll continue to do so until the environmental situation becomes untenable. In the mean time, the real estate developers, estate, agents, house builders, private insurers, road contractors, shop owners, and rental accommodation suppliers, will all get paid. And the tourists will continue to enjoy fun in the sun.

What about the property owners? Well, in real estate, timing is everything. They’ll just have to watch the market and judge when to sell — that’s if they even care; purchasing beach-front property is not a poor man’s game. And if a hurricane happens to blow their stuff away, there’s always FEMA and the Feds (the American taxpayer) to help them rebuild their houses, on taller stilts if necessary.

Beach houses on Hatteras Island, August 2011 after Hurricane Irene

Beach houses on Hatteras Island, August 2011 after Hurricane Irene. Image: Telegraph/AP

If sea level rises faster and higher than the 6 – 8 inches currently mandated by North Carolina’s law makers, who will bare the cost? Probably the people living in towns along the State’s low lying mainland coast. The houses they live in are not summer homes or holiday rentals — it’s all they’ve got.

Map of North Carolina showing physical regions

North Carolina Physical Regions. Map image from NCPedia