Effect Analysis of Flood Control Projects in the Xin'an River Based on OpenMP Parallelization and ADI

To evaluate the combined flood control effect of the Yangzhi River flood diversion control sluice and dyke heightening and reinforcement project in She County, this paper takes the urban area of She County as the research object. It collected multi-source data of the "7.7" flood in She County in 2020, and based on the theory of 2D shallow water equations, established a high-performance hydrodynamic numerical model targeting the unique hydrological and topographic characteristics of the Xin'an River tributaries, including multiple confluences, high-steep slopes, and small angles between tributaries. Specifically, by optimizing the discrete format of tributary confluences in the Alternating Direction Implicit (ADI) algorithm, the problem of insufficient adaptability of existing models to complex mountainous river systems is addressed. Additionally, an OpenMP parallel task allocation scheme matching the 1D decomposition characteristics of ADI is designed to balance simulation accuracy and computational efficiency, and the model is subjected to calibration and validation.Based on the measured "7.7" flood in 2020 and the design floods of 20-year, 30-year, 50-year, and 100-year return periods scaled by the same frequency, control schemes with and without the project are set up respectively. The model is used to evaluate the regulatory impact of the project on flow rate, water level, and inundation range. The results show that the project can significantly reduce the flow of the Yangzhi River into the Lianjiang River, effectively lower the water level at key nodes, and reduce the inundation area. Specifically, for the "7.7" flood in 2020, the project's flood diversion volume reaches 1700 m³/s, the water level at Yuliang Station decreases by 1.76 m, and the inundation area is reduced by 26.5%, with a prominent flood reduction effect in the Economic Development Zone. The project has a significant regulatory effect on water levels of frequent floods such as the 20-year and 30-year return periods; even in the face of extreme floods with a 100-year return period, it can still play a certain regulatory role, but the regulatory efficiency shows a decreasing trend as the flood return period increases. In addition, the project's water level regulation exhibits significant spatial differences. The research results can provide a scientific basis and technical support for local flood control and disaster mitigation work.