Forecasting Our Future: Highway 12 Rodanthe Bridge Project
Construction of the NC-12 Rodanthe Bridge Project almost a decade in the making is nearly complete. It isn't difficult to see why it was so necessary.
"Planning for this started in mid-2014," Pablo Hernandez, Resident Engineer, NC DOT Division 1.
The planning was sparked by the damage done to the existing stretch of HWY-12. Asphalt was torn apart by hurricanes Irene and Sandy.
"Not wrinkled like a sheet of paper. Wrinkled with a three to four-foot undulations in it or the asphalt just gone. You don't know if it went out into the ocean with it or out into the sound," Hernandez said.
Or power poles being knocked down.
"To see those power lines leaning over or falling into an inlet such as new inlet, it leaves quite an impression on you such as the power that we’re up against.”
Add to that, images of the beach eroding and encroaching on the existing stretch of highway.
If you go far enough, you'll find a former speed limit sign now immersed in the sand.
The DOT bought themselves time after those storms by installing sandbags near the shoreline to prevent sinkholes caused by erosion.
"These sandbags are five feet wide, two feet thick and 15 feet long. We place the sandbags in a place where we have overwash with the potential to undermine the asphalt."
It became clear something must be done to find a long-term solution.
"There have been options in the past and attempts made that were successful at relocating the road in certain area but now with the severity of the storms looking for that long-term solution, that’s why we’re going to the bridging option.”
While protecting the existing road, crews began to get to work on the new bridge project. That's an intricate task with environmental limitations.
"We need big heavy equipment but yet we could not use barges in the area because the water is too shallow. So we had to use a temporary bridge system to build the permanent bridge. All the while we want to minimize the impact on the subaquatic vegetation. Minimize the impact on adjacent wetlands we may span across or be near. So that’s the challenge.”
The DOT worked with researchers to hindcast, using data from previous storms to predict what future impacts to the roadway may be.
"We know that storms are getting more frequent and intense and we have to start to think about the future so we use climate model projections. It’s not like a weather forecast it'll be cool and 72 degrees but we’re looking more 10-15 years down the road.”
"Use the storms from the past, run them in different scenarios taking into account new land development, dune shape and sound bottom contour and inlet contour and see what are some of the worst case scenarios we could experience for a bridge.”
The hope is that planning will accommodate for shifting shorelines and weather events, to ensure this bridge is here to stay.
"Being designed for that 100-year service life. Doesn't mean we’re not going to have to go out there and do some maintenance in 50 or 75 years but we won’t have to do that in-depth comprehensive maintenance."
