Exploration of the munition dumpsite Kolberger Heide in Kiel Bay, Germany: Example for a standardised hydroacoustic and optic monitoring approach

Post-war marine munition dumpsites do exist and are acknowledged by authorities, but their real extent and their effect onto the environment are mostly unknown. Military historic reconstruction and ocean current data (from in-situ measurements and modelled data) indicate that the German dumpsite in the Baltic Sea ‘Kolberger Heide’ is an active environment with a huge content of discarded munition material (DMM). Repeated high-resolution multibeam and underwater video surveys prove that Kolberger Heide contains more than 1,000 munition objects in the form of e.g. moored mines, ground mines, torpedoes and aerial bombs. An unsupervised seafloor classification was performed to show that corroded munition objects and proud explosives are in direct contact with the diverse local marine flora and fauna. Also the fact that the dumpsite is in close proximity to the shore in very shallow water (less than 15 m water depth) and displacement and burial of mines can be observed, demand an effective and standardised monitoring procedure. Via the combined approach of hydroacoustic and optical methods, areas can be identified, which should be prioritized when it comes to monitoring.