THE EFFECT OF SAND NOURISHMENT ON BEACH SEDIMENT COMPOSITION OF SANDY HOOK, NEW JERSEY

Beach nourishment restores sediment in the littoral system and supports the continued operation of longshore transport. This study identifies the impact of beach nourishment on the change of the sediment composition using grain size and the morphological development of the Sandy Hook beaches, with comparison to a 1950 baseline sampling (McMaster, 1954). Samples were collected in August 2022. Four samples within 5 meters of each other were obtained at each of the six stations along the high tide line. A 12-inch long downspout pipe was forced to a depth of 6 inches into the sand and the core was retrieved. After splitting and air drying grain size distributions for each core sample were determined using a Malvern Mastersizer 3000 laser particle sizer. Results for 18 of the 24 samples were obtained, leaving 6 samples for further examination.

We will present grain-size distributions, descriptive statistics of grain sizes, such as the median and mode, sediment sorting, characterize the shift of the sediment composition since 1950, and its relation to more recent beach erosion and accretion. Our initial results show that the median grain sizes of Sandy Hook beach samples have a narrow range of ~414 to 483 µm, with an exception for a station at the southern end with coarser median grain sizes between 566 and 668 µm. McMaster reported a median grain size of 299 to 456 µm for nearby stations. These new results suggest that beach grain-size in 2022 was more uniform and coarser than in 1950. The longshore transport direction at Sandy Hook is from south to north and accretion was observed in the field to the northern end of the spit. Using routine measurements of the New Jersey beach profiles by Stockton University, the relationship between the change of the grain-size distribution and the beach morphology will be determined.

The effectiveness of nourishment projects depends on the grain size of the filling material, coastal geological substrate, and the intensity of modern sedimentary processes. Beach erosion prevention and enhanced dune formation help to lessen the consequences of coastal floods and increase opportunities for tourism and critical habitat. Changes in sediment composition and volume reveal information about beach stability. Research findings can be applied to coastal management strategies, such as beach erosion prevention.