Influence of Multi-Cross Structures on the Flood Discharge Capacity of Mountain Rivers in the Yellow River Basin

Abstract

This study investigates the impact of cross structures on flood occurrences in mountainous rivers. The governing equations of open channel flow were formulated based on the Saint-Venant equations. The open channel was segmented, and a node equation was established at each section’s connection point. An overflow model of bridges and weir dams was also developed. The physical model of the open channel was simplified and modeled using actual building data and model calculation requirements. The study found that the primary impact of weirs and bridges on the open channel was the backwater effect on the water level. The influence of these structures on the water level in the Huang Stream urban section in the Yellow River Basin was assessed under various working conditions. The results showed that deleting the #1 weir could reduce the maximum backwater height by 1.14 m, and deleting the #2 weir could reduce it by 1.09 m. While reducing the weir height significantly decreased the backwater range and height, it did not enhance the river’s flood discharge capacity. The Huang Stream contains 17 bridges, 13 of which could potentially affect flood discharge. The eight flat slab bridges in the submerged outflow state had a significant impact on flood discharge, with a maximum water level change of 0.51 m. Conversely, the three single-hole flat slab bridges in the free outflow state downstream had a negligible impact on flood discharge. The study found that bridges had a greater influence on flood discharge capacity than weirs. This research provides valuable insights for the reconstruction of cross structures in mountainous rivers and for managing flood discharge capacity and flood control.