This study investigates the coupling risk factors between urban water supply and transportation networks by analyzing 246 pipe damage incidents (with diameters ≥800 mm) in the central area of Puxi, Shanghai, from 2004 to 2021. It employs an N (network scale) -K (interaction degree) model to construct a risk coupling model for the two networks, revealing the multi-factor risk cascading effects and coupling characteristics of the water supply-transportation coupled network. The findings demonstrate that there exists risk factor coupling between the two networks, with increased coupling corresponding to greater safety risk impacts. The physical attributes of the water supply network itself constitute the primary risk factor affecting its safety. Based on the system decoupling theory, this paper proposes risk control strategies for urban water supply-transportation network coupling, which are of great significance for reducing coupling interactions between the two networks and ensuring their safe operation.