Mine burial in the seabed of high-turbidity area (Belgian coastal zone): findings from a first experiment
Baeye, M.; Fettweis, M.; Legrand, S.; Dupont, Y.; Van Lancker, V. (2012). Mine burial in the seabed of high-turbidity area (Belgian coastal zone): findings from a first experiment, in: Baeye, M. Hydro-meteorological influences on the behaviour and nature of sediment suspensions in the Belgian-Dutch coastal zone = Hydro-meteorologische effecten op het gedrag en samenstelling van sedimentsuspensies in de Belgisch-Nederlandse kustzone. pp. 111-130
In: Baeye, M. (2012). Hydro-meteorological influences on the behaviour and nature of sediment suspensions in the Belgian-Dutch coastal zone = Hydro-meteorologische effecten op het gedrag en samenstelling van sedimentsuspensies in de Belgisch-Nederlandse kustzone. PhD Thesis. Ghent University: Ghent. 170 pp.
Suspended particulate matter; particle size distribution; statistical handling; coastal turbidity maximum; wind impact; seabed variations The seabed of the North Sea is covered with ammunition dating back from World Wars I and II. With increasing human interference (e.g. fisheries, aggregate extraction, harbour related activities), it forms a threat to the safety at sea. In this study, test mines were deployed on a sandy seabed for three months to investigate mine burial processes as a function of hydrodynamic and meteorological conditions. The mine experiment was conducted in a shallow (9 m), macrotidal environment characterized by highly turbid waters (yearly and depth-averaged suspended particulate matter concentration of 100 mg l-1). Results showed some variability of the overall mine burial, which corresponded with scouring processes induced by a (sub-) tidal forcing mechanism. The main burial events however were linked to storm-related scouring processes, and subsequent mine roll into the resulting pit. Two storms affecting the mines during the 3-month experiment resulted in enduring increases in burial volume to 60% and 80%, respectively. More cyclic and ephemeral burial and exposure events appear to be linked to the local hydrodynamic regime. During slack tides, suspended sediment settles on the seabed, increasing the burial volume. In between slack tides, sediment is re-suspended, decreasing the burial volume. The temporal pattern of this never reported burial mechanism, as measured optically, mimics the cyclicity of the suspended sediment concentration as recorded by ultrasonic signals at a nearby benthic observatory. Given the similarity in response signals at the two sites, we hypothesize that the formation of high-concentrated mud suspensions (HCMS) is a mechanism causing short-term burial and exposure of mines. This short-term burial and exposure increase the chance that mines are ‘missed’ during tracking surveys. Test mines contribute to our understanding of the settling and erosion of HCMS, and thus shed a light on generic sedimentary processes.
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