Munitions mobility and burial in a microtidal estuary

Field tests were performed to observe mobility and burial of underwater unexploded ordnances (UXOs) in a microtidal estuary, characterized by multiple forcings and mixed sediments. Such characteristics distinguish the site from others usually studied in the literature, making the analysis very complex. Observations highlighted the large dependence of UXO behavior on the bed sediments. UXOs placed on the muddy riverbed got buried almost instantaneously, without moving. Just the smallest and least dense UXO experienced some migration (maximum 10 m) and re-exposure episodes. On the other hand, UXOs remained proud on the sandy seabed, until a wave storm produced bed fluidization that caused their complete burial. Field observations, together with data collected by an integrated monitoring system operating in the study area, provided a baseline dataset for the validation of predictive models of UXO motion. The Underwater Munitions Expert System (UnMES), forced with Delft3D hydro-morphodynamic results, was run to simulate the behavior of light, medium, and heavy UXO types during a sea storm. Results agreed well with observations, predicting complete burial and minimal migration (0–5 m). • Field tests of UXOs mobility and burial were performed at a microtidal estuary. • Burial dominated in the cohesive-muddy riverbed. • A wave storm caused UXOs migration and subsequent burial due to the sandy seabed fluidization. • Burial and migration predicted by the probabilistic model UnMES showed good agreement with observations.