Abstract: Cities near river confluences are often vulnerable to local heavy rainfall, upstream floods, and downstream tidal backwater impacts.Understanding the encounter pattern of rainfall, flood, and tide is crucial for designing effective urban flood control systems.In this study, the Copula function theory was employed to analyze the joint distribution of heavy local rainfall, large upstream flood from Taihu Lake, and high tide level at the downstream confluence Wusongkou in Shanghai.Subsequently, the most probable scenarios of rainfall-flood-tide combinations were estimated.The results indicated that the Frank copula, in conjunction with the P-III marginal distribution, was the most effective model for characterizing the distribution of rainfall-flood-tide encounters.The joint defense return period was only equivalent to 333 years given that the flood control measures for local rainfall, upstream flood, and downstream tide backwater impact were designed to prevent 1000-year return period event.The co-occurrence return period of rainfall-flood-tide encounters was substantially overestimated under the assumption of variable independence.In consideration of variable dependence, the return periods for the Fitow, In-Fa, and Matsa typhoons, which significantly impacted Shanghai since 2000, had been declined to 1691, 122, and 100 years, respectively.Similar events might occur again.The conditional distribution of local rainfall in conjunction with upstream flood and downstream tide level demonstrated a negative feature, ie, flood and tidal levels might rise as the intensity of rainfall increased.These findings served as a reference for the design of the flood control system in the Shanghai area, to enhance the defense capability against random concurrent flood caused by local rainfall, upstream flood, and downstream tidal backwater impact