Spatial and temporal variability in geomorphic change at tidally influenced shipwreck sites: The use of time‐lapse multibeam data for the assessment of site formation processes

Abstract

Shipwrecks are an integral part of our maritime archaeological landscape and are associated with diverse societal and cultural interests, yielding significant management challenges. Coupled hydrodynamic and geomorphological processes significantly impact the effective in situ preservation of these fragile sites. In this study, we assess sediment budget change and hydrodynamic triggers at metal‐hulled shipwrecks lost between 1875 and 1918, all located in the tidally dominated Irish Sea at depths between 26 and 84 m. This is conducted using time‐lapse, multibeam echosounder surveys at multiannual, annual, and weekly time steps, supported by sediment grain‐size analysis, modeled ocean currents, and shallow seismic data. Results indicate significant changes at all time steps for sites located in sand‐dominated environments, whereas the seabed around shipwrecks settled in multimodal sediments shows virtually no change outside of measurement errors (±30 cm). Variability in geomorphic change is attributed to local environmental factors, including bed shear stress, sediment supply, and spatial barriers to scour. We demonstrate that individual wrecks in similar shelf sea regions can be in very different equilibrium states, which has critical implications for the in situ management of underwater cultural heritage.

Documenting, Protecting and Managing Endangered Maritime Cultural Heritage in the Middle East and North Africa (MENA) Region

“…However, while the resulting data (e.g. high resolution bathymetry) are becoming widely available in parts of the world, thus enabling usage for archaeological purposes (Plets et al 2011 ; Westley et al 2011 ; Davis et al 2020 ; Majcher et al 2021 ), the same is not yet true of the study area. Either the requisite surveys have not been conducted or data have been collected, but are not publicized or readily accessible for commercial, military or governmental reasons, or simply because open-access provisions are lacking.…”

Comparison between the Employment of a Multibeam Echosounder on an Unmanned Surface Vehicle and Traditional Photogrammetry as Techniques for Documentation and Monitoring of Shallow-Water Cultural Heritage Sites: A Case Study in the Bay of Algeciras

“…There are numerous studies in the literature on the use of MBES for imaging submerged shipwrecks from conventionally manned vessels [31][32][33][34][35]. However, we do not know of any study in which this combination of technologies, MBES plus USV and photogrammetry, has been used in the dimensional study of a shipwreck.…”

Shipwreck ecology: Understanding the function and processes from microbes to megafauna

“…For example, Irish Sea shipwrecks in sand-dominated seascapes with high currents experience migrating waves of sediment across sites that trigger scour pits and alternating sediment deposition and erosion, whereas shipwrecks in mixed substrate or gravel-dominated settings experience less physical disturbance (Majcher et al. 2021 ). Climate-induced changes in environmental conditions, such as sea-level rise, warming water temperatures, and ocean acidification, are also hypothesized to disturb shipwrecks and potentially increase their degradation rate (Gregory et al.…”

“…For example, multibeam bathymetry and multifrequency backscatter acquired from multibeam echosounders have been used in concert with current and wave sensors to determine fluid and geological dynamics around shipwrecks (Majcher et al. 2021 ), and split beam echosounders and laser-line scanners have been used to determine patterns in fishes’ use of shipwrecks (Paxton et al. 2019a , Johnson et al.…”