Abstract: The proliferation of river-crossing bridges at high densities may have adverse effects on rivers. To investigate the cumulative impact of bridge clusters on the hydrodynamic characteristics of river channels, a two-dimensional hydrodynamic model is employed to analyze how the construction of bridge clusters influences various hydrodynamic characteristics, such as water height and velocity. The study aims to establish a relationship between the number of bridges, bridge spacing, and hydrodynamic characteristics of river channels. The findings reveal that bridge clusters create a backwater effect upstream of the bridges and induce a surge in water height near the piers. The surge height near the piers is significantly higher than the backwater effect near the bridges. However, the impact of the surge height diminishes when the distance between bridges is eight times the width of the piers. Furthermore, the cumulative impact on the river channel increases substantially with an increase in the number of bridge clusters. Once the distance between bridges exceeds 160 times the pier width, the cumulative impact on the river channel nearly disappears. Therefore, it is crucial to consider the number of bridges and bridge spacing in bridge construction to minimize the cumulative impact of bridge clusters.