Draft Sea Level Rise Report Shows Regional Impacts on North Carolina Coast

Feb 2, 2015

Credit S. Fegley/UNC Institute of Marine Sciences

We examine a new draft report indicating eastern North Carolina’s susceptibility to sea level rise.  Researches weigh in on last month’s draft report indicating a more than five inch increase in some areas over the next 30 years.  What would that do to areas like Morehead City and the Outer Banks?

The coast of North Carolina is especially vulnerable to sea level rise, causing an increase in the severity of flooding during major storms, a loss of sensitive coastal habitats, and extensive beach erosion.  The sea level has been rising in North Carolina for the last few centuries.  Historically, the U.S. Army Corp of Engineers research pier in Duck has measured an annual rise of about 4mm, the thickness of two nickels stacked on top of one another.  Knowing the rate at which sea level rise occurs is important for planning infrastructure and homes.  The North Carolina Division of Coastal Management released a draft report last month examining sea level rise over the next 30 years.   Public Information Officer for the CRC Michele Walker. 

 “The current draft looks at sea level rise at five tide gauges along the North Carolina coast from Duck down to Southport.   We believe that North Carolina is the first state to look at sea level rise on a regional level rather than coming up with one rate for the entire coast.”

The current draft predicts a lower rate of sea level rise in southern coastal areas than on the northern portions of the Outer Banks.  Walker says this is due to land subsidence, which is a gradual movement of land in a downward direction.

“the land there is actually sinking in response to geological forces. It’s sinking at a faster rate.  So relative sea level rise will be greater in that area.”

In the draft report, if the rate of sea level rise remains stable, an increase of 5.4 inches is predicted for Duck and the northern Outer Banks, 4.3 inches at Oregon Inlet, 2.4 inches for Wilmington and about 3.2 inches for Beaufort over the next 30 years. It’s an increase that will bring widespread impacts according to Executive Director of the North Carolina Coastal Federation Todd Miller.

“Things that are close to the water, I mean the yards are going to be wetter, if not constantly wet. When we get storms, there will be flooding where there wasn’t flooding in previous years.  Erosion along the shoreline will increase and particularly combined with storm events, we’ll see pretty significant modifications to the landscape.”

Another devastating impact from sea level rise will be the reduction of salt marshes which protect water quality by filtering runoff and provide a safe habitat for more than 75 percent of fisheries species. 

The 30 year sea level rise projections appear less dramatic than an initial report released by the North Carolina Coastal Resources Commission in 2010.  It forecasted the state should prepare for 39 inches of sea level rise by the year 2100.  That study was rejected by legislators.

“I think the numbers startled a lot of people”

Miller believes the 30 year projection shows a more gradual increase and ignoring an accelerated pace of sea level rise occurring around the year 2040.  However, Public Information Officer for the Coastal Resources Commission Michele Walker says they wanted to make the information easier to understand.

“The CRC felt that it would be more useful to coastal communities to look at a closer time frame.  They also thought the information gathered would be more reliable.”

Short range predictions allow scientists to more accurately detail the rate of sea level rise, according to Spencer Rogers, specialist in coastal construction and erosion with North Carolina Sea Grant. He’s also a member of the advisory science panel tasked with drafting the report. 

 “The science of sea level rise and sea level rise acceleration in the future due to potential changes in climate are definitely a moving science.”

The General Assembly requires the North Carolina Coastal Resources Commission to update the sea level rise report every five years.  Since the last study was released in 2010, improvements to predicting sea level rise have been made.  Rogers says they’ve added tide gauges along the coast to get a more comprehensive picture of the impact of sea level rise, and to help monitor landform changes at the same time sea level is rising.

 “We knew a couple of the tide gauges at Wilmington and Beaufort had potentially been affected by dredging at the state ports.  And we’ve been able to conclude that the Morehead City gauge has not been affected.  The Wilmington gauge may be affected a small enough amount that it’s usable in the analysis.”

In 2012, House Bill 819 was enacted prohibiting sea level rise projections from being used as a basis for regulations until July 2016.  Public Information Officer Michelle Walker says the NC Coastal Resources Commission at the time of the legislation and currently are not taking any regulatory action based on the sea level rise data.

“The primary goal was really to encourage local governments to be aware of the issue and to be aware of what could be happening, you know, 30, 40, 50 years from now and factor that in when they’re doing future planning for roads, large facilities for houses even.”

The draft report is currently out for peer review and Walker says they are waiting for those comments.

“And I think the report is very likely to change once we get those comments back, the science panel may make some changes and some additions to their report.”

Walker says the study will likely go to the North Carolina Coastal Resources Commission in March, where it will be open for public comment.  The final report will be submitted to the General Assembly in Spring 2016.