1 Towards Mitigation of Environmental Risks
15
an accident will then depend on the point where it happens. In case of oil pollution,
this point is linked with potential vulnerable spots by oil drift properties; in case of
exciting high wake waves by rules governing the wave propagation (Torsvik et al.
2009).
If vulnerable spots are selected based on environmental criteria, a smart use of
the distribution in question provides a natural way to mitigate or minimize environmental damage. Doing so is feasible through a systematic quantification of the
relevant costs, or, equivalently, through systematically accounting for the transport
of pollution from the release (or accident) site to vulnerable areas. The challenge,
therefore, is the quantification of the offshore areas in terms of their potential for the
transport of adverse impacts from these areas to valuable ones. This quantification is
the corner stone of the method described in this book. It makes it possible to find optimum solutions for semi-enclosed sea areas and also partially answers the question
how far from the open ocean coast an economically feasible and environmentally
friendly sailing line should be located.
1.9 Separation of the Impact of Wind, Waves and Currents
The propagation of different substances within the water column is governed by the
3D system of currents. The substances in the surface layer are additionally affected
by wind and waves. The understanding of the exact role and contribution of each of
these factors still has large gaps in both scientific and operational models today and
definitely needs an independent study. While the wind and wave conditions in the
area of an oil spill can be forecast with an acceptable accuracy today (Ardhuin et al.
2009), the reconstruction of the role of in the transport of tracers (or adverse impacts) is much less satisfactory (Vandenbulcke et al. 2009). This deficiency reflects
the extreme complexity of motions in the seas and oceans. Marine science has only
recently reached a stage where the development of mathematical models, the accuracy and reliability of circulation modelling, the computational facilities and the
quality of information about forcing factors allow addressing the problem of drift
prediction in a dependable way.
Both wind- and wave-induced transport are highly anisotropic and mostly mimic
the behaviour of the wind and wave patterns. To a first approximation, the relevant
transport velocities can be simply added to each other. In the absence of currents, the
probability of hitting a vulnerable area is determined by the joint transport velocity
and the time it takes until the hit occurs is roughly proportional to the resulting joint
downwind/downwave distance from the location of the oil spill. This observation
once more signifies that the remotely affected area and thus the cost of the consequences of a ship accident substantially depend on where and when exactly the
accident happens. Although both these factors have large spatio-temporal variability
and the knowledge of the properties of their interaction with each other and with the
oil spill is far from being perfect, the solution to the problem of finding the optimum
fairway (ship location) is straightforward. The optimal location is just as far in the
combined upwind/upwave direction from the susceptible spots as possible.
15
an accident will then depend on the point where it happens. In case of oil pollution,
this point is linked with potential vulnerable spots by oil drift properties; in case of
exciting high wake waves by rules governing the wave propagation (Torsvik et al.
2009).
If vulnerable spots are selected based on environmental criteria, a smart use of
the distribution in question provides a natural way to mitigate or minimize environmental damage. Doing so is feasible through a systematic quantification of the
relevant costs, or, equivalently, through systematically accounting for the transport
of pollution from the release (or accident) site to vulnerable areas. The challenge,
therefore, is the quantification of the offshore areas in terms of their potential for the
transport of adverse impacts from these areas to valuable ones. This quantification is
the corner stone of the method described in this book. It makes it possible to find optimum solutions for semi-enclosed sea areas and also partially answers the question
how far from the open ocean coast an economically feasible and environmentally
friendly sailing line should be located.
1.9 Separation of the Impact of Wind, Waves and Currents
The propagation of different substances within the water column is governed by the
3D system of currents. The substances in the surface layer are additionally affected
by wind and waves. The understanding of the exact role and contribution of each of
these factors still has large gaps in both scientific and operational models today and
definitely needs an independent study. While the wind and wave conditions in the
area of an oil spill can be forecast with an acceptable accuracy today (Ardhuin et al.
2009), the reconstruction of the role of in the transport of tracers (or adverse impacts) is much less satisfactory (Vandenbulcke et al. 2009). This deficiency reflects
the extreme complexity of motions in the seas and oceans. Marine science has only
recently reached a stage where the development of mathematical models, the accuracy and reliability of circulation modelling, the computational facilities and the
quality of information about forcing factors allow addressing the problem of drift
prediction in a dependable way.
Both wind- and wave-induced transport are highly anisotropic and mostly mimic
the behaviour of the wind and wave patterns. To a first approximation, the relevant
transport velocities can be simply added to each other. In the absence of currents, the
probability of hitting a vulnerable area is determined by the joint transport velocity
and the time it takes until the hit occurs is roughly proportional to the resulting joint
downwind/downwave distance from the location of the oil spill. This observation
once more signifies that the remotely affected area and thus the cost of the consequences of a ship accident substantially depend on where and when exactly the
accident happens. Although both these factors have large spatio-temporal variability
and the knowledge of the properties of their interaction with each other and with the
oil spill is far from being perfect, the solution to the problem of finding the optimum
fairway (ship location) is straightforward. The optimal location is just as far in the
combined upwind/upwave direction from the susceptible spots as possible.