The U.S. Geological Survey has a long history of responding to and documenting the impacts of storms along the Nation’s coasts and incorporating these data into storm impact and coastal change vulnerability assessments. Although physical changes caused by tropical and extratropical storms to the sandy beaches and dunes fronting barrier islands are generally well documented, the interaction between sandy shoreline erosion and overwash with the back-barrier wetland and estuarine environments is poorly constrained. The goal of the Barrier Island and Estuarine Wetland Physical Change Assessment project is to integrate a wetland-change assessment with existing coastal-change assessments for the adjacent sandy dunes and beaches, initially focusing on Assateague Island along the Maryland and Virginia coastline. Assateague Island was impacted by waves and storm surge associated with the passage of Hurricane Sandy in October 2012, causing erosion and overwash along the ocean-facing sandy shoreline as well as erosion and overwash deposition in the back-barrier and estuarine bay environments.
Data Series 999 associated with this metadata record describes sediment data collected using sand augers in active overwash zones on Assateague Island in Maryland. Samples were collected by the U.S. Geological Survey (USGS) during two surveys in March/April and October 2014 (USGS Field Activity Numbers [FAN] 2014-301-FA and 2014-322-FA, respectively). The physical characteristics (for example, sediment texture or bedding structure) of and spatial differences among these deposits will provide information about overwash processes and sediment transport from the sandy barrier-island reaches to the back-barrier environments. Metrics derived from these data, such as mean grain size or deposit thicknesses, can be used to ground-truth remote sensing and geophysical data and can also be incorporated into sediment transport models. Data products, including sample location tables, descriptive core logs, core photographs and x-radiographs, the results of sediment grain-size analyses, and Geographic Information System (GIS) data files with accompanying formal Federal Geographic Data Committee (FGDC) metadata can be downloaded from
http://pubs.usgs.gov/ds/999/ds999_data.html.
This zip archive includes the geographic locations, site elevations, site descriptions, and core and trench metrics in Microsoft Excel, Esri file geodatabase, and Kehyhole Markup Language (KML) format for sand auger sites collected from Assateague Island, Maryland in March/April and October 2014 (USGS FAN 2014-301-FA and 2014-322-FA).
USGS scientists collected sediment samples from Assateague Island and Chincoteague Bay during two surveys—one in the spring, March 26 to April 4, 2014, and one in the fall, October 21–30, 2014 (USGS FAN 2014-301-FA and 2014-322-FA, respectively). Samples were collected from a variety of depositional environments, including mainland wetlands, back-barrier wetlands, and sparsely vegetated to unvegetated washover deposits. Site locations were identified as 14CTB-XXX# where XXX is a consecutive number from 01 to 500 (01–200 for spring; 300–500 for fall) and # represents the type of sample collected. Data Series 999 describes sediment data from sand augers (sample type W) collected from active overwash zones on Assateague Island.
Sand extents derived from pre- and post-storm aerial imagery were analyzed to identify areas of Assateague Island that were overwashed during Hurricane Sandy. Coring sites targeted three active overwash zones (transects 1, 3, and 4) and one control transect (transect 2). During the spring survey, a total of 19 cores were collected from 17 sites, including 8 cores from 7 back-barrier marsh sites. During the fall survey, all of the spring sand auger sites were re-cored, and additional cores were collected from overwash deposits at transects 1 and 4 located approximately 1 kilometer (km) north of the Verrazano Bridge Causeway on Sinepuxent Bay and at the Fox Hills Level north of Green Run Bay, respectively. The expanded sampling strategy targeted sites that had overwashed historically (since 1989) in addition to those sites that were overwashed during Hurricane Sandy. In October, a total of 81 core sections were collected from 69 sites.
All sample locations were recorded at the time of collection with a Garmin GPSMAP 76S handheld Global Positioning System (GPS) receiver. Position and elevation data were also recorded with an Ashtech Differential Global Positioning System (DGPS) receiver and geodetic antenna, which provided more accurate horizontal and vertical control than handheld GPS systems. A stop-and-go rapid-static survey technique was used, with a static occupation duration of 5 minutes at each sample site. DGPS data were recorded concurrently throughout the survey at multiple National Park Service (NPS) benchmarks using a similar instrument combination.
Cores were collected using an AMS sand/loose sediment soil probe, which can accommodate a 2.54-centimeter(cm) (1-inch) diameter by approximately 60-cm (2-feet) plastic sleeve. In addition to cores collected from the ground surface, during the October survey a second core was collected at some sites from a trench dug to just above the groundwater table. The purpose of collecting a second, deeper, core was to try to penetrate organic-rich deposits representing the pre-overwash surface below the washover sediments. Cores from sites where a second core was collected were identified as 14CTB-XXXW-1 (surface core) and 14CTB-XXXW-2. After extraction, each core was capped, sealed, and labeled with transect location, core number, and orientation. The cores were transported to the USGS St. Petersburg Coastal and Marine Science Center (SPCMSC) for processing and analysis. During the October survey, shallow trenches were also dug at each of the transect 1 and 4 washover sites for the purpose of supplementing washover thickness and sedimentologic data from the sand augers with additional sediment samples from targeted strata. Trench depths, however, were limited by a shallow water table, and in most cases the trenches back filled or collapsed before the pre-overwash surface could be identified. The site information, along with core and trench descriptions, is available from
http://pubs.usgs.gov/ds/999/ds999_data.html.
