Navigation risk assessment method based on flow conditions: A case study of the river reach between the Three Gorges Dam and the Gezhouba Dam

Of the many factors that influence navigational safety, navigable flow conditions are one of the most important. Therefore, the development of a navigation risk assessment model based on flow conditions is of considerable importance for improving the safety of shipping. In this paper, the influence of flow on shipping is considered. Four determination indices for navigational safety, including water surface slope, backflow, velocity, and depth, and a five-level classification of navigation risk assessment are proposed. To evaluate quantitatively the influence of flow conditions on shipping, a navigation risk assessment model is established using gray relational analysis. In a case study of navigation in the river between the Three Gorges Dam and the Gezhouba Dam, a two-dimensional hydrodynamic model for the study reach is established to simulate four types of flow field (Le., under Three Gorges Dam discharge of 7,000, 10,000, 20,000, and 30,000 m(3)/s). Shipping risk maps for specific ship types under different water regimes were drawn in accordance with the simulated results based on the navigation risk assessment model. The research results not only promote effective precise management of navigation in the study reach but they also provide a reference for quantitative research of navigational safety.