Navigational Risk Assessment In The Dry Season Of Yangtze River

As one of the few seasonal large-scale rivers worldwide, the waterway depth of Yangtze River drops dramatically during its dry season caused by seasonal factors as well as the release quantity from reservoirs, thus congestion incidents have often occurred in shallow channels of Yangtze River particularly when marine accidents such as groundings and collisions happen during the dry season. This may not only influence the efficiency and safety of inland waterway transportation, but also affect the sustainable development of Chinese shipping industry.The techniques of navigational risk assessment and precaution play a vital role in the prevention and reduction of congestion incidents and other marine accidents. This PhD thesis focuses the navigational risk in the dry season of Yangtze River, reviews various methods for navigational risk assessment and precaution, identifies the critical safety elements, analyzes the spatial risk distribution and proposes the corresponding risk control options (RCOs). Furthermore, the congestion risk is chosen as the typical navigational risk during the dry season of Yangtze River that a congestion model has established and a cost-benefit analysis for RCOs has carried out. More specifically, the main content of this research is as follows:1) Navigational risk identification in the dry season of Yangtze River. A hierarchical model involving multiple influencing factors is established for navigational risk assessment of Yangtze River by which the safety critical elements in the dry season of Yangtze River are identified utilizing discrete fuzzy sets and an Analytic Hierarchy Process, AHP. A utility approach is presented that the best RCO is selected by ranking the utility values of various RCOs.2) Navigational risk estimation in the dry season of Yangtze River. Based on the established hierarchical model, the Evidential Reasoning (ER) approach and a fuzzy rule base are combined to cope with the multiple criteria analysis. By collecting both subjective and objective data of upstream, midstream and downstream of Yangtze River, the spatial distribution of navigational risk in the dry season is analyzed that the focal area for risk control is highlighted.3) Congestion risk modeling. An accident based idea is proposed for congestion risk study based on the cause of congestion incidents in Yangtze River. By collecting the historical data of marine accidents, a congestion risk model is established using a correlation analysis and the Bayesian Network (BN) approach. The congestion critical elements are further analyzed by scenario analysis.4) Cost-benefit analysis for congestion RCOs. Corresponding congestion RCOs are proposed based on the identified congestion critical elements. By establishing a multiple alternative cost-benefit analysis model, the cost effectiveness of each RCO is calculated using continuous fuzzy sets and the TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) approach that the preferences of RCOs under various risk conditions are discussed.5) Congestion risk precaution and decision support. A Congestion Risk Index (CRI) is presented based on the proposed congestion risk BN model by which a novel evaluation system for congestion warning is established. RCOs for every warning level are selected referring to the proposed cost-benefit analysis. Therefore, the risk precaution and decision support of congestion incidents can be achieved.