High-Resolution Surficial Geology Mapping of the New Hampshire Inner Continental Shelf and Coastline: An Important Step Towards Coastal Resiliency

TitleHigh-Resolution Surficial Geology Mapping of the New Hampshire Inner Continental Shelf and Coastline: An Important Step Towards Coastal Resiliency
Publication TypeConference Abstract
AuthorsWard, LG, McAvoy, ZS, Corcoran, NW, Masetti, G, Johnson, P, Morrison, RJ
Conference NameGulf of Maine 2050 International Symposium
Conference LocationPortland, ME
Conference DatesNovember 4-8
Keywordscoastal resiliency, nh inner continental shelf and coastline, surficial geology mapping

The continental shelf off New Hampshire (NH) is extremely complex with extensive bedrock outcrops, remnant glacial deposits, sand and gravel ridges and shoals, and muddy offshore basins. The depositional features were significantly modified by marine processes as sea-level fluctuated following deglaciation. Many of the glacial features found on the inner shelf continue onshore. The NH coast is extremely heterogeneous as well, ranging from pocket beaches, attached barriers interrupted by rocky headlands (many previously covered with till) or glacial features (e.g., drumlins), and a barrier island. The composition of the beaches reflects the variability in sediment sources ranging from fine sand to cobbles with bimodal beaches being common. The combination of a reduction in sediment supply and an acceleration in sea-level rise has led to much of the NH coast being stressed by erosion and more frequent flooding. Furthermore, coastal erosion and flooding are expected to be exacerbated by climate change. To help build coastal resiliency, high-resolution surficial geology maps of the NH shelf were developed depicting seafloor features (geoforms) and surficial sediment using CMECS. In addition, potential sources of sand and fine gravel were evaluated for beach nourishment. Presently, similar work is being done on the NH beaches: mapping major coastal features, determining beach sediment grain size under accretional and erosional conditions, and assessing beach stability. A goal of this work is to link the surficial geology of the mainland (published by the NH Geological Survey), the coast, and the inner shelf to better define the physiography, the sediment distribution (and sources), and the controlling processes. Ultimately, mapping the surficial geology, along with existing and new high-resolution topography and bathymetry surveys, will help coastal managers, planners, and the public prepare for sea-level rise and climate change, and build coastal resiliency.

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