| Spills of oil or other hazardous chemicals that are caused by mishaps at sea may result in significant impact on the marine environment and on the coastal communities which exploit these regions. Calamitous chemical (oil) spills as well as the chronic exposure of frequent small spills has a harmful impact on biota and economical issues. The threat of chemical (oil) pollution on vulnerable marine and coastal areas is of great concern to the responsible authorities and requires permanent, stand-by or temporary measures. Management and control of coastal pollution disasters requires knowledge and understanding of the dispersion and effects of such spills. Important parameters used in determining the chemical (oil) spill behaviour at sea are wind, waves, tidal motion, bathymetry, and the shape of the land-water boundary. Accurate hydrodynamic information is therefore essential for making reliable predictions of the dispersion and fate of chemical pollutions. This holds true especially in the vicinity of coastal structures such as long dams and harbour breakwaters where large scale horizontal vortices may be present. These horizontal turbulent motions have dimensions on the order of hundreds of meters and time-scales on the order of minutes. In the usual flow simulations in which the classical unsteady shallow water equations are numerically solved, these motions are not resolved. Therefore, a proper and advanced modelling technique such as HLES (Horizontal Large Eddy Simulation) is required which faithfully simulates the creation and evolution of eddies with horizontal dimensions significantly exceeding the water depth near coastal structures. In addition, high resolution curvelinear boundary fitted model grids are essential for an accurate representation of e.g. curved break water. In this paper we demonstrate the need for these kinds of advanced hydrodynamic modelling techniques by considering various contingency chemical spill scenarios in and nearby the IJmuiden harbour in the Netherlands. To accomplish this, a high resolution model of the harbour geometry inclusive coastal structures and the adjacent Dutch coastal zone has been defined to address the significance of hydrodynamic complexity. The results may provide valuable information to facilitate policy planning and the resolution of harbour management issues such as moving leaking ships in distress to a place of refuge. |
