Scour processes play a critical role in the preservation status of submerged historic shipwrecks. Erosion of sediment leads to enhanced exposure of archaeological sites to physical, chemical and biological processes. Current methods for identifying erosional and depositional features at wreck sites are based primarily on visual interpretation of data, which is labour-intensive and entirely subjective. The increasing availability of high-resolution multibeam echosounder-derived digital elevation models (DEMs) of historic wreck sites allows for an entirely new level of detailed interrogation and analyses of the geomorphological features associated with these. In this study, we present a residual relief modelling method for the semi-automated extraction of such depositional and erosional features at wreck sites. Relief modelling is supplemented with a breakpoint classification approach, with final separation supported by DEM visualisation enhancement techniques. We applied the method to three World War I shipwreck sites and evaluated it against traditional manual vectorisation techniques. The results suggest that the semi-automated modelling method is robust, time-effective and capable of quantifying the products of scour processes with increased objectivity. Our method holds great potential for the objective characterisation of erosional and depositional patterns and processes at wreck sites, which have important implications for site formation studies and in situ preservation of underwater cultural heritage.

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.

No abstract

Shipwrecks are important cultural heritage sites offshore. In many instances, given their often long-term emplacement on the seafloor, they offer natural laboratories to study complex interactions between human-induced obstacles and seabed dynamics. Such interactions and induced sediment mobility also pose significant threats to offshore engineering infrastructure, such as turbine monopile foundations. Traditional methods can struggle to capture the nuance of these processes, with real-world surveys measuring effects only after installation, and laboratory models suffering from scale-down inaccuracies. Computational fluid dynamics (CFD) modelling offers an effective means of investigating the effects of obstacles on seabed dynamics, and by using shipwrecks as proxies for infrastructure, it can utilize long-term datasets to verify its predictions. In this study, high-resolution temporal bathymetric data were used in, and to verify, CFD modelling to investigate the interactions between hydro- and sediment dynamics at a shipwreck site in a tidally dominated wreck site. From this comparison, simulations of bed shear stress and scalar transport correlate well with known areas of erosion and deposition, serving as a basis for future scour prediction studies and creating effective tools in offshore renewable infrastructure planning and de-risking.