How are we documenting our shorelines and shoreline sites?

Coastal North Carolina boasts a diverse environment, hosting numerous archaeological and historical sites that offer insights into the rich history of the state. Many of these sites are situated along our shorelines in the Coastal Plain, areas subject to continuous transformation, which can be further accelerated during severe weather events like Hurricanes Florence and Michael, which struck North Carolina in 2018. To understand the dynamics of these shorelines and the condition of the sites along them, we utilize a combination of methods to identify, document, and assess both site and shoreline stability within our project areas.

Prioritizing State-Owned and Managed Lands

Before commencing fieldwork, it is important to establish a systematic method for pinpointing the areas affected by Hurricanes Florence and Michael. We initiated this process by identifying Managed Areas designated by the NC Natural Heritage Program. Within the twelve project counties (Beaufort, Bertie, Brunswick, Carteret, Craven, Dare, Hyde, New Hanover, Onslow, Pamlico, Pender, and Tyrrell counties), we focused on state-owned and managed lands. These properties underwent further evaluation based on their environmental and historical significance.

The environmental priority of each property was determined by assessing the extent of flooding and the types of sediments in the area. We estimated flooding, or storm inundation, caused by both Florence and Michael using Category 4 Hurricane storm surge levels in the SLOSH Model, provided by NOAA’s National Hurricane Center. Sediment data was sourced from geological maps from the NC Department of Environmental Quality, with particular emphasis on sediments prone to erosion.

The historical priority of each property was determined by examining previously documented archaeological and historical remains, as well as evaluating the likelihood of undiscovered sites. This assessment drew upon a range of data sources, including the locations of previously recorded pre- and post-contact archaeological sites, historic maps delineating plantations and maritime infrastructure, and archival documents discussing the locations of fishing, shipbuilding, and maritime industries and infrastructure.

For each property, environmental and historical priority were assigned a numerical value between 0 and 5, with 0 denoting the lowest priority and 5 indicating the highest priority and, consequently, the highest level of risk. Properties with high scores in both categories were considered for fieldwork. The selected areas for this project include Hammocks Beach State Park in Onslow County, the Alligator River Game Land in Tyrrell County, and the Scuppernong River Section of Pettigrew State Park Dedicated Nature Preserve in Tyrrell County. Learn more about these locations!

Terrestrial Survey

Terrestrial surveying techniques were employed to identify, document, and assess shoreline sites located a minimum of 60 meters (approximately 200 feet) inland from the high tide line in each priority area. Each survey consisted of two components – a pedestrian survey and a shovel test survey.

During the pedestrian survey, archaeologists walked, waded, or snorkeled in shallow waters to identify artifacts and features visible on the ground surface. All identified artifacts and features were photographed, recorded, and mapped.

Shovel test surveys were conducted over the same area as the pedestrian survey, following a systematic survey approach. Archaeologists excavated 1-meter deep holes to ascertain the presence of buried artifacts or features. These pits were dug where the water table was at least 1 meter deep, as pits in shallower areas would simply fill with water. After completing each shovel test, the soil profiles of the pit wall and any artifacts were photographed, recorded, and mapped.

Underwater Survey

To complement the terrestrial survey, an underwater survey was conducted in the waterways adjacent to the surveyed land, with the aim of identifying sites that are already submerged along the shoreline. These surveys utilized remote sensing tools, including a magnetometer, a side scan sonar, and a sub-bottom profiler, to identify cultural resources.

The magnetometer identifies anomalies that may be located on or under the seafloor by measuring variations in the Earth’s magnetic field. The Earth’s magnetic field is consistent for any given location; when the magnetic field deviates from the expected, an anomaly is identified. These anomalies indicate the presence of a magnetic object, typically made of iron, such as a shipwreck or associated materials like a cannon.

The side scan sonar creates an image of the seafloor using sound. On either side of the device, there are transducers that emit sound waves into the water. These waves travel through the water, bounce off objects they encounter, and return to the device. Based on the time it takes for the sound waves to return, an image of the seafloor is produced. This allows archaeologists to identify cultural materials on the seabed and obtain certain characteristics of these sites, including how much is exposed above the sand.

Similar to the side scan sonar, the sub-bottom profiler also uses sound to image the seafloor. Instead of focusing on the surface, the sound waves penetrate the seafloor to create an image of the buried environment. While it can be used to identify cultural materials, this device is primarily employed to identify past geological and sedimentary characteristics, producing images of previous floodplains and coastal landscapes.

Shoreline Erosion Analysis

To better understand how shoreline sites are being affected by shoreline change, a two-step approach was employed to characterize the shorelines. Initially, while in the field, archaeologists recorded tidal levels for both high and low tides along the entire extent of shorelines in the project areas. Additionally, they took photographs of the full shorelines to categorize areas experiencing erosion, accretion, and stability.

Subsequently, the team utilized the field data and conducted an extensive historical analysis of the shorelines using LiDAR and aerial imagery. This study enabled the team to identify how the shoreline has evolved over time, how these changes compare to present-day alterations, and the implications for archaeological sites.

Thanks to our partners AECOM, NC State Park, NC Department of Transportation, and NC Wildlife Resources Commission for their hard work and assistance in the completion of these projects. 
This material was produced with assistance from the Emergency Supplemental Historic Preservation Fund, administered by the National Park Service, Department of the Interior. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Department of the Interior.