Marine & Coastal
Archaeological survey and research of the coastal and marine zone provide insights into the physical, social and cultural relationships humans had with this environment in the past. The marine environment acts as a routeway to allow people to travel or to trade bulk goods whilst having a deep-rooted presence in the cultural identity of past societies; the marine landscape helps shape these identities. Maritime landscapes are shaped by how people in the past interacted with the sea, both as a resource base and as a canvas for human experience and social action. Archaeological research within the maritime zone is important to understand past landscapes, shipping, environmental determinism, human settlement, trade and exchange networks, development and diffusion of technologies, past societal response to climatic events, human economies such as fishing, hunting and shipping, and the associated subcultures of these, for example, navigation.
Coastal and marine studies typically include the following topics:
- Submerged Landscapes
- Coastal, intertidal and maritime hinterland
- Inland waters (lochs, rives, canals, and navigations)
- Ships, inland and seagoing vessels
Survey methods such as coastal zone assessments have the potential to uncover vast numbers of previously unknown archaeological sites alongside our coastlines whilst furthering the record of known sites. Coastal Zone Assessments involve desk based assessment to identify the archaeological resource, utilising historic environment records, mapping, aerial photography and other datasets such as LiDAR. This is followed up by field Survey, where a team of archaeologists and in some cases geologists walk the coast recording its geology and geomorphology and assess its erosion status; and locate, verify, identify and record archaeological features and their erosion status. This is a rapid survey using maps, a recording form and photography to provide a visual record and basic level of survey. The final component of a coastal zone assessment involves reporting. The production of a report outlining the survey area, methodology, results and recommendations with accompanying maps and gazetteer’s. Data relating to archaeological sites and monuments is usually incorporated into the sites and monuments record.
Diving apparatus is required to allow archaeologists to record submerged cultural heritage assets underwater. Archaeologists use two types of diving equipment, self-contained underwater breathing apparatus (SCUBA) or surface air supply. The environment in which the archaeologist is working determines the type of equipment used. The same methods used on-land are utilised underwater to record the submerged cultural heritage asset such as archaeological drawing, photography, photogrammetry and recording sheets.
Remote sensing is the most common survey detection method in marine archaeology. To obtain an image of the seafloor, we need to illuminate or irradiate the study area with an appropriate radiation. To get sufficient returned radiation, its absorption by the environment needs to be small. There are a variety of remote sensing methods that work well within the maritime environment.
Singlebeam Echosounder Survey
Singlebeam echosounders determine the depth of water by transmitting a sound pulse in water. These are typically used for navigation purposes and are commonly called fish finders. They provide depth points that map the seafloor, and anomalies on the seafloor such as submerged cultural heritage resources such as shipwrecks can be identified from such data. This data is quite coarse due to the distribution of point readings.
Multibeam echosounders create more detailed seafloor maps than singlebeam echosounders. This is due to the emittance of soundwaves in a fan shape beneath a ships hull, the amount of time it takes for the sound waves to bounce of the seafloor and return to a receiver is used to determine water depth. It uses beamforming to extract directional information from the returning soundwaves producing a swath depth of readings from a single ping. Multibeam echosounders are commonly used in seafloor mapping. This type of archaeological data analysis can be used to inform on marine conservation zones, it allows analysis of seabed impacts and outlines management issues, along with highlighting the human impacts on the seabed. Output data from the multibeam echosounders is used in the production of shaded relief, bathymetric contour, backscatter and seabed classification charts.
Airborne Laser bathymetry
Airborne Laser bathymetry involve the collection of accurate high density bathymetric data, using laser light pulsed from a fixed wing or rotary wing aircraft. 3D digital data is captured by measuring one time difference between returns of light reflected from the sea surface and seabed. It relies on clear, non-turbid water to work successfully.
Sub bottom profiler
Sub bottom profilers are low frequency echosounders developed for providing profiles of the upper layers of the seafloor. They identify and characterise layers of sediments or rock under the seafloor. They are used for detection and monitoring of buried shipwreck sites and mapping palaeolandscapes.
Satellite imagery identifies wrecksites based on the principle that wrecks generate suspended particle matter concentrate signals, that are detected by high resolution ocean colour satellites such as Landsat 8
A magnetometer detects changes in the magnetic field that varies over a wide area according to the geology or locally over ferrous objects such as canon or shipwrecks. Its cylindrical shape and positive buoyancy are specifically designed to reduce risk of snags with moored gear and equipment losses.