Skidaway Institute researcher maps armored shorelines

Skidaway Institute of Oceanography researcher Karrie Brinkley has spent a lot of time in recent months traveling up and down Georgia’s coastal waterways in boats and canoes with maps and binoculars in hand. Brinkley is working on a project to identify and map all the armored shorelines in the state’s six coastal counties.

Brinkley has been looking for bulkheads, causeways and rip-rap – the piles or rock or concrete frequently used to stabilize a shore or river bank. The purpose of the study is to establish a baseline set of data to help understand and project the effect of rising sea level on the Georgia coast.

Karrie Brinkley examines a bulkhead armored shoreline on Skidaway Island.

“The shorelines are going to act differently as the sea level rises, depending on whether they are armored or not,” said Brinkley. “In this project, we want to see how much of the coast is armored and what type of armory is being used for individual sections as well as the entire coast.”

Brinkley is working under the guidance of Skidaway Institute professor Clark Alexander. He says that currently the oceans are rising at approximately three millimeters per year, or roughly a foot per century, however many scientists project that rate could double, triple or quadruple in coming decades. This could have a tremendous impact on coastal areas.

“One environmental area of concern is the salt marshes,” said Alexander. “If the sea level gradually rises along a natural coast, the salt marshes that thrive in the intertidal zone will gradually migrate to the upland.

“However, if a section is armored, the intertidal zone may become completely submerged, and we would lose the function of the salt marsh in that area.”

The study is funded by the Georgia Department of Natural Resources, under the umbrella of a larger Environmental Protection Agency project. Geographically, Brinkley is studying all the coastal shores, from the beaches westward to either Interstate 95 or US Highway 17, which ever is further to the west.

For the first ten months of the project, Brinkley spent her time in front of a computer, studying aerial photographs of the coastal counties. Using a Geographical Information System program, she electronically marked the photos to indicate causeways, bulkheads, rip-rap and other shoreline armor.

An aerial photo of Wilmington Island showing causeways in purple and shoreline armor in yellow.

“Depending on the resolution of the photography, you can identify a lot from the photos,” Brinkley said. “Bulkheads show up as straight lines, and the bright stones of concrete rip-rap are fairly obvious as well.”

There are still many areas that Brinkley cannot characterize from the aerial photographs due to poor resolution, foliage overhangs or other reasons. Even the tide cycle when the aerial photography was shot can affect how much information can be gleaned from the photos. “A high tide may cover some rip-rap and make it invisible in the aerial photograph,” Brinkley said.

For those sections, she gets in a car, a boat or a canoe and visits the sites personally.

Once completed, the project will be shared with officials in Georgia’s coastal counties. Brinkley expects to have the project completed early in 2010.

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