34 
Callies & Schwichtenberg - Drift modelling 
Between the two red areas in Figure 6.4, a band of green colouring indicates those regions 
where application of dispersants has the potential to make much of a difference for Wadden 
Sea pollution. With regard to absolute numbers of probabilities it must be mentioned that 
generally all simulations with wave heights either below 0.5 m or above 3 m were labelled as 
unsuccessful. Such situations occurred in about 25 % of all cases, so that the maximum 
probability against which probabilities in Figure 6.4 should be compared is roughly 75 %. 
Taking this into account, in some regions the use of dispersants seems to be a promising 
option. 
55°0'0"N 
54°30'0"N 
54°0'0"N 
7WE 
7°30'0''E 
8°0'0"E 
8°30'0"E 
9°0'0"E 
Probability 
successful 
dispersant 
application 
65% 
55% 
45% 
35% 
25% 
15% 
5% 
Figure 6.4: Probabilities that application of a 100% effective dispersant right after oil was released would 
reduce the amount of oil entering sensitive coastal areas by at least 95%.The grey (blue) line indicates the 
10m (20m) depth line. The figure is reproduced from Schwichtenberg et al. (2016). 
Conclusions 
A large ensemble of simplified drift simulations, treating oil as a passive tracer, helped identi 
fy regions where using dispersants has the potential to be beneficial in the sense that it pre 
vents the pollutant from entering most sensitive areas. The above study is not yet a full net 
environmental benefit analysis (NEBA) as no possible toxic effects have been taken into ac 
count. Nevertheless, a map like the one shown in Figure 6.4 suggests regions for which con 
ducting a NEBA would be worthwhile.