Observation of Mobilisation of Munition-Type Test Objects under Sea-State Conditions in the Baltic Sea

Unexploded ordnances (UXO) and discarded military munition (DMM) in seas and oceans, collectively referred to as underwater military munition (UWMM), pose a global concern and threat to human safety, marine ecosystems, and economic activities. Dumped in the ocean many decades ago, parts of these UWMM are still mobile today. Understanding their mobility helps to assess potential risks for offshore construction areas and enables educated decisions on required survey intervals for already cleared areas. For this reason, calculation models are being developed by various research groups to predict the mobilisation and migration of munitions. These mathematical models usually lack the precise determination of model parameters, such as rolling friction or the description of the complex hydrodynamics of the sea state, and must therefore be calibrated using field measurements. For this purpose, measurements are being carried out with munition-type test objects in a test field in the Baltic Sea, near Rostock, Germany. The test objects are equipped with a self-developed sensor system, with which not only the movement of the objects themselves but also the time-dependent dynamic wave-induced pressure on side is measured. First test results are analysed with respect to their plausibility and evaluations of the correlation between sea state and wave-induced object motions are presented.