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Open-File Report 2015–1219

A Seasonal Comparison of Surface Sediment Characteristics in Chincoteague Bay, Maryland and Virginia, USA

Background and Environmental Setting

Location of the geographic features referenced within the text

Figure 2. Location of the geographic features referenced within the text. [Click to enlarge]

Storm Overview

Hurricane Sandy, the largest Atlantic hurricane on record, made landfall near Brigantine, New Jersey (NJ), just north of Atlantic City, NJ, as Post-Tropical Cyclone Sandy on October 29, 2012, at 2330 Universal Time Coordinated (UTC) (fig. 1; Blake and others, 2013). When the center of the storm made landfall, Sandy had been downgraded from a hurricane (declared on October 24, at 1200 UTC and October 27, at 1200 UTC) to an extratropical cyclone (October 29, 2100 UTC) with more than 1500 kilometers (km) in wind-field diameter and maximum sustained winds of 130 kilometers per hour (km/h) (70 knots) (fig. 1; Blake and others, 2013). In Maryland and Virginia, 0.61–1.22 meter (m) inundations, expressed in height above ground level and is the total water level that occurred on typically dry ground as a result of storm tide, were widespread along the coast (Blake and others, 2013). The National Ocean Service (NOS) gauge on the ocean side of Maryland's Ocean City Inlet measured a maximum storm surge of 1.32 m above normal tide levels. The maximum storm surge for the state of Virginia was 1.51 m at Wachapreague, on the Eastern Shore (Blake and others, 2013), approximately 50 km south of Chincoteague Bay. During the storm, eastern Maryland, Virginia, and extreme southern New Jersey and southern Delaware reported the heaviest rainfall in the United States with a widespread area receiving 12.7–17.8 centimeters (cm). Bellevue, MD, approximately 100 km northwest of Chincoteague Bay, reported the maximum amount of rain at 32.6 cm (Blake and others, 2013).

Environmental Setting

Chincoteague Bay proper, Sinepuxent Bay, and Newport Bay are located along the U.S. East Coast, approximately 160 km south of Atlantic City, NJ. They are separated from the Atlantic Ocean by Assateague Island, a 60-km long, narrow barrier island off of the Delmarva (Delaware Maryland Virginia) Peninsula (fig. 2). Sinepuxent Bay extends along the east side of Sinepuxent Neck, from South Point at the southern end of the neck to Ocean City Inlet, MD. Newport Bay is a flooded river valley of Trappe Creek located on the western side of Sinepuxent Neck, with a watershed drainage area of 113 square kilometers (km2) (Maryland Department of Natural Resources, 2004). Sinepuxent and Newport Bay both lie to the north of Chincoteague Bay proper, which extends from the base of Sinepuxent Neck, MD, to Chincoteague Inlet, VA, to the south and has a total watershed area of 315.5 km2 (Maryland Department of Natural Resources, 2004).   

In this report, Chincoteague Bay refers to the portions of Sinepuxent Bay (24.1 km2), Newport Bay (15.9 km2), and Chincoteague Bay proper (377 km2), where the majority of the current study was conducted, with the exception of Tom’s Cove to the south (fig. 2). The Chincoteague Bay study area is approximately 400 km2, crossing the Maryland-Virginia border (fig. 1, 2). It is a shallow, microtidal (< 2 m tidal range) coastal lagoon system with an average water depth of approximately 1 m and salinities ranging between 19.07–32.48 practical salinity units (PSU) (Boynton and others, 1993; Wells and others, 2003). The surface sediments of Chincoteague Bay are mostly sandy on the back-barrier side of Assateague Island to the east and mostly silty with small amounts of clay on the western side (Boynton and others, 1993; Wells and others, 1997). Chincoteague Bay is bordered by salt marshes along the Delmarva Peninsula to the west and, to a lesser extent, Assateague Island to the east.

South of Chincoteague Bay and northeast of Chincoteague Inlet is Tom’s Cove, a small (8 km2) embayment separated from the inlet by a small spit (fig. 2). Tom’s Cove has a variable water depth of approximately 2.5 m, generally 1 m deeper than that of Chincoteague Bay and with salinities similar to that of the open ocean.

Previous Studies

Chincoteague Bay and the surrounding areas have been the topic of studies beginning as early as 1949 (Signewald and Slaughter). Many of these studies focused on determining the sediment characteristics and sediment sources for the bay, as well as accumulation and erosion rates for the bay, the islands in Chincoteague Bay, and the marshes surrounding the bay (Singewald and Slaughter, 1949; Rasmussen and Slaughter, 1955; Bartberger and Biggs, 1970; Biggs, 1970; Bartberger, 1973; 1976; Conkwright 1975). From 1993 through 2003, the Maryland Geological Survey and Department of Natural Resources conducted multiple high resolution studies mapping the physical and geochemical characteristics of the shallow water sediments of the Maryland coastal bay system including Sinepuxent Bay, Newport Bay, Assawoman Bay, Isle of Wight Bay, and the Maryland portion of Chincoteague Bay (Wells and others, 1994a; Wells and others, 1994b; Wells and others, 1996; Wells and others, 1997; Wells and others, 1998; Wells and others, 1999; Wells and others, 2001; Wells and others, 2002; Wells and others, 2003). In these studies, 988 surface samples were collected and analyzed for grain-size distribution, carbon, nitrogen, sulfur, and metal content (Wells and others, 1999). Of the 988 samples collected, 341 were from the Maryland portion of middle Chincoteague Bay, and the rest were collected in Maryland’s more northern coastal bays. This high-resolution study was used as a reference for sediment characteristic distribution throughout Chincoteague Bay and served in part as a guide for this project’s sampling strategy.

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