Research On Risk Assessment Of Ship Collision And Oil Spill Pollution Based On Stochastic Methodology

Marine transportation,which accounts for more than 90%of the global freight volume,plays a key role in international trade.The ship navigation safety and antipollution are the prerequisite for the normal operation of the marine transportation system.The maritime traffic accidents,especially vessel collision accidents,often result in serious consequences such as oil spill pollution,casualties and property loss.Therefore,the risk assessment on vessel collision and oil spill,has got a lot of attention in maritime circles.Due to the uncertainty and complexity of ship accident risk,there are still many deficiencies in the existing assessment methods here and abroad.Considering the randomness of vessel collision and oil spill accident,with stochastic theory the paper applies to study the quantitative evaluation method for the probability and consequence of vessel collision and oil spill accident,and the main research work and achievements are as follows:(1)The model of vessel dynamic domain closely related to ships' type,size and relative speed is established by introducing traffic conflict theory in land traffic field.Regarding the vessel as a particle,vessel collision conflict is defined as one vessel particle:intruding the circle around another vessel particle of radius equal to the average radius of two vessel domains.According to above definition,a novel algorithm based on AIS data is presented to evaluate collision conflict by vessel collision frequency,which is defined as the product of the collision candidates acquired from AIS and the causation probability.Examples are given to verify the availability and effectiveness of the collision frequency model based on dynamic vessel domain.(2)Collision conflictis a good substitute for collision accident.The spatial distribution of collision conflict can intuitivelyshow the macro-collision risk in waters.In the research,a new modeis developed to exhibit the collision risk at sea.Spatial distributions of speeds ofvessel involved in conflicts andtypes of conflict are plotted based on electronic chart.Visualization pattern is applied to present the temporal-spatial distribution of the macro-collision risk in waters.Model results show that the most collision risky areas are Niushan Island(24°46.8'N?25°30.0'N),Xiongdi Islet(23°22.8'N?25°49.2N)and Xiamen Bay Waters(24°08.4'N?24°33.6'N).(3)In order to accurately evaluate the possibility of collision occurrence and the seriousness of collision consequence,a probability model is constructed based on event tree of collision consequence.The model includes six intermediate events of Ship Type(ST),Ship Size(SS),Loading Condition(LC),Striking or Struck(SK),Hull Damage(HD)and Survivability(SU).Considering the uncertainty and randomness of some intermediate events,their probability distribution functionsare determined by introducing random variables and using Monte Carlo simulation.(4)The theory and method of quantitative risk assessment on vessel collision are developed.A quantitative risk assessment model for vessel collision is established,including such submodels as vessel collision frequency,event tree analysis,and collision accident consequence quantification probability of different scale oil spill and mortality.The visualization of vessel collision risk is accomplished by the F/N curve that can clearly show the relations between vessel collision frequency and accident consequences.(5)An empirical study aimed at the Taiwan Strait is carried out the vessles collision quantitative risk assessment model based on Stochastic parameter presentedin this paper.The results show:? The collision frequency for the Taiwan Strait is found to be 5.0687 per year,which is veryclose to the mean value of 4.8667 per year based on 15 years' historical accident data.Referring to the ship types,bulk carrier has the highest collision frequency of 2.920 per year while passenger/RORO has the lowest collision frequency of 0.045 per year,and the collision frequency of oil tanker is 0.119 per year,accounting for 2.34%of total.? In the study waters,the frequency of vessel collision accident with oil spill more than lOt is 1.02 per year.The frequency of accident with oil spill more than 100t is 0.97 per year,andmore than 1,000t is 0.185 per year.In accidents with oil spill greater than 100t,bulk carrier has a maximum frequency of 0.411 per year,followed by container ship of 0.252 per year and oil tanker of 0.145 per year.? In the study waters,The frequency of major vessel collision accident with fatalities more than 10 persons is 8.58×10-2 per year.Referring to ship types,bulk carrier has a maximum frequency of 6.01×10-2per year,followed by LNG/LPGof 2.31×10-2 per year and oil tanker of 2.67×10-3 per year,and general cargo ship and container ship have the minimum frequenciesof 1.0×10-8per year.(6)A method based on stochastic scenario simulation is proposed for quantitative evaluation of ship oil spill consequences.The risk probability and shortest arrival time of the oilspill pollution to the sensitive area are obtained through the stochastic scenario simulation and grid statistics.The calculation model of composite oil spill harm index is established by adopting the parameters such as environmental sensitive index and oil spill amount.Then the consequences of the oil spill can be evaluated in accordance with the comprehensive oil spill harm index.The results of applying the model in the Taiwan Strait are shown as follows:In the northern Taiwan Strait,the severities of the pollution caused by ship oil spill in different seasons follows a descending order of summer(27.8),autumn(25.5),spring(21.1),and winter(16.2).In the summer,the oil spill is more likely to contaminate Niushan Island Ecological Reserve,leading to critical consequences of high severity rating,while in other seasons,protection zone of Dongjia Islands is prone to pollution of oil spill.In the southern Taiwan Strait,the descending order of the harm index in different seasons are autumn(21.9),winter(20.5),spring(19.2),and summer(14.3).The risk probability and harm index of the oil spill in Dongshan Coral reef reserve are much more than those in other waters.Based on the above results,pertinent measures are put forward to promote the response and handling to ship oil spill in the Taiwan Strait,including Emergency Cooperation Organization System and Emergency Resource Scheduling Scheme.