T110 Sigma Gamma Epsilon Undergraduate Research (Posters)

Monday, 1 November 2010
8:00 AM - 6:00 PM
Hall D

FIELD INVESTIGATION OF THE RELATIONSHIP BETWEEN BERM MORPHOLOGY, BEACH GRAIN SIZE, AND WAVE CLIMATE AT CAPE CANAVERAL, FLORIDA

Paper number: T110-33
Program: Technical Sessions
Time: 8:00 AM – 6:00 PM

Authors

Abstract

Establishing shoreline vulnerability to storm inundation requires an understanding of the processes that affect beach topography, especially berm formation. This study investigates a possible relationship between berm height, grain size and wave climate along the 10 km-long, NASA-Kennedy Space Center beach at Cape Canaveral, Florida during the season of highest potential inundation from tropical storms. Cross-shore topographic profiles along 13 fixed transects were collected monthly beginning in May 2009 using a RTK-GPS system, and sediment samples were collected on each transect at dune, backshore, berm crest, foreshore, and surfzone locations during low tide. To determine beach slope, two different methods were used. An overall beach slope (OBS) was defined as the elevation/horizontal difference between the base of the dunes and the datum-based mean-high-water (MHW) shoreline position. A foreshore beach slope (FBS) was established for a portion of the foreshore that extended from the berm crest to a variable elevation just below the MHW line. The berm height was established from the cross-shore profiles and was recognizable for all transects during both months.

In July, the correlation between OBS and berm mean grain size (r=0.89) is stronger than the correlation between FBS and berm grain size (r=0.76). In September, the correlation between FBS and berm grain size (r=0.45) is stronger than the correlation between OBS and berm grain size (r=0.31). Similarly, there is a strong correlation between berm height and OBS (r=0.92) and between berm height and berm grain size (r=0.93) in July, but by September, the correlation is decreased for berm height and FBS (r=0.69) and for berm height and berm grain size (r=0.62). The wave data from a nearby NOAA buoy (49001) reveals a period of a persistent low significant wave height and period for about two weeks prior to the July survey. This appears to be the time when the berm was initially formed, and the beach profile exhibits a more compound slope with the new berm. By September, the existing berm had been altered by intervals of higher wave energy, resulting in a more linear shoreface slope. Results from this study are in agreement with generally accepted relationships between grain size and beach face slope for gently-sloped, open ocean beaches subject to low wave energy.