Elizabeth A. Pendleton

Importance of Coastal Change Variables in Determining Vulnerability to Sea- and Lake-Level Change

Abstract In 2001, the U.S. Geological Survey began conducting scientific assessments of coastal vulnerability to potential future sea- and lake-level changes in 22 National Park Service sea- and lakeshore units. Coastal park units chosen for the assessment included a variety of geological and physical settings along the U.S. Atlantic, Pacific, Gulf of Mexico, Gulf of Alaska, Caribbean, and Great Lakes shorelines. This research is motivated by the need to understand and anticipate coastal changes caused by accelerating sea-level rise, as well as lake-level changes caused by climate change, over the next century. The goal of these assessments is to provide information that can be used to make long-term (decade to century) management decisions. Here we analyze the results of coastal vulnerability assessments for several coastal national park units. Index-based assessments quantify the likelihood that physical changes may occur based on analysis of the following variables: tidal range, ice cover, wave height, coastal slope, historical shoreline change rate, geomorphology, and historical rate of relative sea- or lake-level change. This approach seeks to combine a coastal systems susceptibility to change with its natural ability to adapt to changing environmental conditions, and it provides a measure of the systems potential vulnerability to the effects of sea- or lake-level change. Assessments for 22 park units are combined to evaluate relationships among the variables used to derive the index. Results indicate that Atlantic and Gulf of Mexico parks have the highest vulnerability rankings relative to other park regions. A principal component analysis reveals that 99% of the index variability can be explained by four variables: geomorphology, regional coastal slope, water-level change rate, and mean significant wave height. Tidal range, ice cover, and historical shoreline change are not as important when the index is evaluated at large spatial scales (thousands of kilometers).

Economic Vulnerability to Sea-Level Rise Along the Northern U.S. Gulf Coast

ABSTRACT Thatcher, C.A.; Brock J.C., and Pendleton, E.A., 2013. Economic Vulnerability to Sea-Level Rise Along the Northern U.S. Gulf Coast. In: Brock, J.C.; Barras, J.A., and Williams, S.J. (eds.), Understanding and Predicting Change in the Coastal Ecosystems of the Northern Gulf of Mexico, Journal of Coastal Research, Special Issue No. 63, pp. 234–243, Coconut Creek (Florida), ISSN 0749–0208. The northern Gulf of Mexico coast of the United States has been identified as highly vulnerable to sea-level rise, based on a combination of physical and societal factors. Vulnerability of human populations and infrastructure to projected increases in sea level is a critical area of uncertainty for communities in the extremely low-lying and flat northern gulf coastal zone. A rapidly growing population along some parts of the northern Gulf of Mexico coastline is further increasing the potential societal and economic impacts of projected sea-level rise in the region, where observed relative rise rates range from 0.75 to 9.95 mm per year on the Gulf coasts of Texas, Louisiana, Mississippi, Alabama, and Florida. A 1-m elevation threshold was chosen as an inclusive designation of the coastal zone vulnerable to relative sea-level rise, because of uncertainty associated with sea-level rise projections. This study applies a Coastal Economic Vulnerability Index (CEVI) to the northern Gulf of Mexico region, which includes both physical and economic factors that contribute to societal risk of impacts from rising sea level. The economic variables incorporated in the CEVI include human population, urban land cover, economic value of key types of infrastructure, and residential and commercial building values. The variables are standardized and combined to produce a quantitative index value for each 1-km coastal segment, highlighting areas where human populations and the built environment are most at risk. This information can be used by coastal managers as they allocate limited resources for ecosystem restoration, beach nourishment, and coastal-protection infrastructure. The study indicates a large amount of variability in index values along the northern Gulf of Mexico coastline, and highlights areas where long-term planning to enhance resiliency is particularly needed.

Geologic Controls on Regional and Local Erosion Rates of Three Northern Gulf of Mexico Barrier-Island Systems

ABSTRACT Twichell, D.C.; Flocks, J.G.; Pendleton, E.A., and Baldwin, W.E., 2013. Geologic controls on regional and local erosion rates of three northern Gulf of Mexico barrier island systems. In: Brock, J.C.; Barras, J.A., and Williams, S.J. (eds.), Understanding and Predicting Change in the Coastal Ecosystems of the Northern Gulf of Mexico, Journal of Coastal Research, Special Issue No. 63, pp. 32–45, Coconut Creek (Florida), ISSN 0749-0208. The stratigraphy of sections of three barrier island systems in the northeastern Gulf of Mexico (Apalachicola, Mississippi, and Chandeleur) have been mapped using geophysical and coring techniques to assess the influence of geologic variations in barrier lithosomes and adjoining inner shelf deposits on long-term rates of shoreline change at regional and local scales. Regional scale was addressed by comparing average geologic characteristics of the three areas with mean shoreline-change rates for each area. Regionally, differences in sand volume contained within the part of the barrier lithosome above sea level, sand volume on the inner shelf, and to a lesser extent, sediment grain size correlate with shoreline change rates. Larger sand volumes and coarser grain sizes are found where erosion rates are lower. Local scale was addressed by comparing alongshore variations in barrier island and inner shelf geology with alongshore variations in shoreline change. Locally, long-term shoreline change rates are highest directly shoreward of paleovalleys exposed on the inner shelf. While geology is not the sole explanation for observed differences in shoreline change along these three coastal regions, it is a significant contributor to change variability.

Comparison of the Hydrodynamic Character of Three Tidal Inlet Systems

New Inlet formed on 2 January 1987 when a northeasterly storm passed over the southern portion of Cape Cod, Massachusetts, USA (Fig. 1). Breaching of Nauset Spit during this event presented an excellent opportunity to describe and understand how tidal inlets evolve hydrodynamically and morphologically after their formation (FitzGerald and Montello, 1991, 1993; Weidman and Ebert, 1993). In this study an analysis of the evolution of a newly formed, frictionally-dominated bay is conducted and results are compared to two well-documented inlet systems.

USGS_Delmarva_SedTexture_Geomorph: Sediment Texture and Geomorphology of the Sea Floor from Fenwick Island, Maryland to Fisherman's Island, Virginia (polygon shapefile, Geographic, WGS84)

These data are a qualitatively derived interpretive polygon shapefile defining surficial sediment type and distribution, and geomorphology, for nearly 1,400 square kilometers of sea floor on the inner-continental shelf from Fenwick Island, Maryland to Fisherman s Island, Virginia, USA. These data are classified according to Barnhardt and others (1998) bottom-type classification system, which was modified to highlight changes in secondary sediment-types such as mud and gravel across this primarily sandy shelf. Most of the geophysical and sample data used to create this interpretive layer were collected as part of the Linking Coastal Processes and Vulnerability: Assateague Island Regional Study project (GS2-2C), supported by the U.S. Department of the Interior Hurricane Sandy Recovery program. Additional sample data were provided by the Maryland Geological Survey and the Virginia Division of Geology and Mineral Resources. Additional hydrographic data were available through the National Oceanographic and Atmospheric Administration s National Ocean Service surveys collected between 2006 and 2014. The primary objective of the Hurricane Sandy Recovery program is to provide science for coastal resilience, and these interpretive data support the program goal by supplying regional geologic framework information for the management of coastal and marine resources. Accurate data and maps of seafloor geology are important first steps toward protecting fish habitat, delineating marine resources on the inner-shelf, understanding sediment transport pathways, and assessing environmental changes because of natural or human effects. The Assateague Island Regional Study project is focused on the inner-continental shelf of Maryland and Virginia, north of Chesapeake Bay entrance. Data collected during the mapping portion of this study have been released in a series of USGS data releases (https://woodshole.er.usgs.gov/project-pages/delmarva/). A combination of geophysical and sample data including high resolution bathymetry, acoustic-backscatter intensity, bottom photographs, and sediment samples are used to create this seafloor interpretation.