Research about Gandys Beach

USGS2024

Topographic and bathymetric survey in support of the effectiveness assessment of the living shoreline restoration in Gandys Beach, New Jersey

High resolution topobathymetric field surveys were conducted by the U.S. Geological Survey in collaboration with Northeastern University and in cooperation with the U.S. Fish and Wildlife Service and The Nature Conservancy in a selected shoreline along Gandys Beach, New Jersey, from January to April 2018. These data are a critical model input for hydrodynamic and wave models and can affect the accuracy of model outputs such as wave height, water surface elevation, current velocity, and sediment transport. Gandys Beach is a living shoreline where constructed oyster reefs (CORs) were built to protect the shoreline and enhance habitat for oyster and other species. Because of the complex topography and bathymetry of the study area, higher spatial resolution topobathymetric data are required to resolve the vertical variations near the CORs. During the field survey, the global navigation satellite system positioning method was used to establish the elevation of a benchmark referenced to the North American Vertical Datum of 1988. The topobathymetric data were collected using a total station. Horizontal accuracy of plus or minus 0.05 foot (ft) and vertical accuracy of plus or minus 0.10 ft were calculated using root mean square error between duplicate surveys. Two existing datasets were integrated with the survey data to create an updated topobathymetric dataset for model input and analysis: (1) the U.S. Geological Survey Coastal National Elevation Database 1-meter resolution data developed after Hurricane Sandy and (2) The Nature Conservancy 2017 elevation monitoring data at 10-meter resolution. A root mean square error analysis comparing survey data with the new topobathymetric dataset versus the survey data compared to the original Coastal National Elevation Data dataset showed errors of 0.31 and 2.61 ft, respectively. This improved dataset can be used for wave and hydrodynamic modeling in support of the effectiveness assessment of the CORs and living shoreline restoration along Gandys Beach.

New Jersey↗

USGS2021

Assessment of wave attenuation, current patterns, and sediment deposition and erosion during winter storms by living shoreline structures in Gandys Beach, New Jersey

This study was conducted by the U.S. Geological Survey and Northeastern University in cooperation with the U.S. Fish and Wildlife Service and The Nature Conservancy. This report summarizes field investigation and analysis of waves, current patterns, and sediment deposition and erosion along the Gandys Beach, New Jersey, salt marsh vegetated shoreline and mudflat, where living shoreline structures (for example, oyster reefs) were constructed to protect the marsh shoreline and enhance habitat for oyster and other species. Constructed oyster reefs (CORs, also known as oyster castles) provide shoreline protection and habitat for fish and shellfish communities via wave energy attenuation. However, the processes and mechanism of CORs on wave attenuation and current circulation remain unclear, thus limiting the assessment of COR effectiveness for shoreline protection. This report presents the results of the field investigation on wave characteristics, current patterns, and marsh edge erosion along a shoreline with CORs in Delaware Bay. To measure the effectiveness of these CORs, six pressure transducers, six tilt current meters, multiple sediment traps, and marsh edge erosion pins were deployed from February to April 2018 in Gandys Beach in upper Delaware Bay. The spatial variations of wave heights measured on both sides of the CORs indicate a strong dependence of wave attenuation on the ratio between the freeboard of the CORs and the offshore wave heights. It was found that swell energy originating from the Atlantic Ocean can penetrate the CORs without any dampening even when the CORs are emergent, whereas the wind seas are more impacted by the CORs. Tidal current velocity and circulation patterns near the CORs (for example, the current velocity was higher than 10 centimeters per second [cm/s] and even up to 30 cm/s in the gaps between the CORs compared to less than 10 cm/s in the control area) differ from those in the control area without protection from the CORs and are greatly affected by the surrounding bathymetry. The combined effect of living shoreline structures on wave attenuation and changes in circulation patterns over the study period resulted in the reduction of shoreline erosion both vertically and laterally compared to that in the control area and also resulted in changes in the grain size distribution in both the water column and the salt marsh and mudflat areas.

New Jersey↗