Research Techniques
We use GPS survey techniques to map the beaches and to record the precise locations of our sand samples. A base station is set up at the foundation of the old Cape Fear Lighthouse, adjacent to the island's historic lighthouse Old Baldy.
The shape of the shoreline can change drastically during storm events. We make real-time kinematic (RTK) surveys using a rover receiver to map the beaches. The receiver records a three-dimensional, geo-referenced location every second or meter traveled with 2cm accuracy. To determine the shape of the beach, we drive an ATV along the shoreline at the water's edge and at the top of the beach slope. We use these lines to extrapolate the steepness of the beach.
Size distribution of sand particles identifies how the renourished sand is transported. Sand that is pumped onto the beach from the river is generally smaller in size and has a darker color than the original sand. During storms great amounts of smaller particles are washed out and are moved by longshore currents. We take samples along evenly spaced lines perpendicular to the shoreline. A sample is taken at the water's edge and at every change in the beach slope along each line. Each sample site is recorded with the GPS. The size distribution of sample content is analyzed at NCSU and those attributes are included in maps of the sample sites.
