Abstract

The continental shelf off New Hampshire (NH) has extensive marine-modified glacial deposits and associated shoals. These features are potential targets for sand and gravel resources for beach nourishment and other efforts to build coastal resiliency. The distribution of sand and gravel deposits was evaluated based on the synthesis of relatively recent high-resolution bathymetry, new surficial sediment and geoform maps, and an extensive data archive that includes over ~1280 km of seismic profiles, ~750 grain size analyses, and 23 vibracores. This work heavily utilizes the results of previous research on mineral resources on the NH shelf by Birch (1984) and others. Unfortunately, much of the archived data was collected before the Global Navigation Satellite System (GNSS) was used routinely for navigation on research vessels. Consequently, much of the critical data from the archives has a large uncertainty associated with the positioning. Furthermore, the seismics are of variable quality. Nevertheless, the data archives coupled with recent high-resolution bathymetry and surficial sediment mapping, provided the basis to develop an initial or first order evaluation of the sand and gravel resources and identify areas where follow-up field campaigns are warranted. This report focuses on four sites where sand and fine gravel deposits may be suitable for extraction for beach nourishment. The most promising sites are referred to as the Northern Sand Body (NSB) and the Southern Sand Deposits (SSD). Estimates of the volume of sand and fine gravel potentially available in the NSB and the SSD are on the order of 17.3 million m3 and 16.4 million m3, respectively. However, these values represent the total volume defined by subbottom seismics and include very fine sand and mud. Therefore, the volume of material that may be available for beach nourishment is likely considerably less. Both of these areas, as well as other potential sites identified, need high-resolution seismic surveys and vibracores to fully evaluate the potential sand and fine gravel resources.

Department

Center for Coastal and Ocean Mapping

Publication Date

2021

Digital Object Identifier (DOI)

https://dx.doi.org/10.34051/p/2021.30

Grant/Award Number and Agency

Bureau of Ocean Energy Management Award Number M14AC00010 and University of New Hampshire/National Oceanic and Atmospheric Administration Joint Hydrographic Center Award Number NA10NOS4000073

Document Type

Report

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