Influence Mechanism of Urban River Water Level on the Drainage Capacity of Stormwater Pipelines

The dynamic coupling relationship between urban stormwater drainage networks and river water levels constitutes a critical issue in flood prevention. This study focuses on the area within Beijing's 3rd Ring Road, establishing an urban flood model using surveyed data of 67,212 pipe segments, 66,759 inspection wells, and 232 sub-catchments to analyze the backwater effect mechanism of river levels on drainage network capacity. Through Python-based batch simulations of 1,056 water level scenarios, results indicate that 64.6% of sub-catchments demonstrate drainage capacities meeting only 1-4-year recurrence interval standards. A nonlinear fitting formula (R²≥0.90) integrating pipe network service area, density, and storage capacity is developed, revealing a quadratic decay pattern in drainage capacity with rising water levels. These findings provide theoretical support for optimizing urban drainage design and flood warning systems.