Risk Identification Method for Valve-Closing Water Hammer Pipe Sections Based on the DEMATEL-AHP-Entropy Weight Method

Valve-closure-induced water hammer remains a major safety threat in long-distance gravity-fed pressurized water transmission pipelines, while conventional assessments based on nodal extreme values offer limited support for segment-level safety management and maintenance prioritization. This study proposes a pipe-segment risk identification framework that integrates hydraulic transient hazard and structural–pipeline vulnerability. A candidate indicator pool is established from water-hammer mechanisms and engineering practice, and DEMATEL is employed to reveal inter-indicator causal relationships and screen key driving indicators. Indicator weights are determined using a hybrid AHP–entropy scheme to balance expert judgment with objective information, and a composite risk index is constructed for risk grading and mapping along the pipeline. The framework is demonstrated on the North Main Pipeline of the Qianping Reservoir conveyance system. A representative operating scenario is examined in which only five branch valves are closed, and the upstream mainline section comprising 171 computational nodes is analyzed under different valve closure times. The results indicate pronounced spatial heterogeneity and strong sensitivity to closure time: shorter closures yield higher maximum pressure, larger pressure fluctuation amplitude, and greater maximum pressure change rates, resulting in an overall upward shift in risk grades. High- and extreme-risk segments consistently concentrate near the downstream end, driven by boundary forcing at valve closure, wave reflection/superposition, and segmental differences in pipeline properties. The proposed approach converts transient simulations into actionable segment-level risk maps and rankings, supporting risk-oriented monitoring deployment, protection optimization, and operational scheduling constraints in long-distance conveyance pipelines.