变化环境下复杂山区小流域山洪灾害频发,提高山洪预报效率及精度是山洪灾害防治体系建设的必然要求。水文模型是模拟降雨径流实现山洪预报的有效工具,明晰产流机制是高精度山洪预报的重要前提。为了探究在小、中、大、特大型4种等级山洪下官山河流域洪水径流对不同产流模式的响应情况,以新安江模型为基础,分别采用蓄满产流、超渗产流与混合产流模式对官山河流域展开山洪模拟分析。结果表明:垂向混合产流的各项精度评价优于超渗产流和蓄满产流,不同等级山洪下的NSE均值>0.7,表现出良好的适用性;超渗产流模式能够有效刻画暴雨下以地表径流为主的山洪产流过程,大型山洪下NSE均值达0.8,在捕捉洪峰方面优势明显。研究成果可为官山河流域山洪灾害防治提供理论与方法支撑,同时可为复杂山区小流域山洪预报提供参考。

[Objectives] This study aims to improve the accuracy and efficiency of flash flood forecasting in the Guanshan River Basin and other similar small mountainous watersheds frequently affected by flood disasters by analyzing the runoff generation mechanisms of flash floods. By comparing the performance of saturation-excess, infiltration-excess, and hybrid runoff generation modes in simulating flash floods of different magnitudes, we also seek to overcome the limitations of single-mode simulation under complex terrain and different rainfall intensities. [Methods] The runoff generation module of the Xin’anjiang model was modified to simulate 38 flood events in the Guanshan River Basin (24 for calibration, 14 for validation) using saturation-excess, infiltration-excess, and hybrid runoff generation modes. Flood magnitudes were classified into small, medium, large, and extra-large according to the Specifications for Hydrological Information and Forecasting. Simulation results were evaluated using Nash-Sutcliffe efficiency coefficient (NSE), peak discharge error, and runoff depth error to compare the applicability and advantages of different runoff generation mechanisms. [Results] The vertical hybrid runoff generation mode demonstrated higher accuracy and stability across different flood magnitudes. It outperformed the other two modes in terms of NSE during both calibration and validation periods, with particularly strong performance in simulating extra-large floods. The saturation-excess mode performed better for small floods but was less stable for large and extra-large events. The infiltration-excess mode achieved the highest accuracy in simulating peak discharges of large floods, but performed relatively poorly in small and extra-large events. Further analysis of the runoff generation mechanisms indicated that runoff generation processes were closely related to rainfall characteristics, soil infiltration rates, and underlying surface conditions. Under intense and short-duration rainfall, infiltration-excess was the dominant mechanism, while under low-intensity and long-duration rainfall, saturation-excess prevailed. The vertical hybrid mode comprehensively integrates both mechanisms, dynamically adjusting the runoff generation approach based on varying rainfall conditions. It enabled effective simulation of flash flood processes under different rainfall scenarios. Additionally, this mode showed higher precision in simulating the recession processes, as it better reflected river basin storage states and the dynamics of interflow and groundwater runoff. [Conclusions] The vertical hybrid runoff generation mode demonstrates significant advantages in simulating flash floods in the Guanshan River Basin, providing robust support for improving the accuracy and efficiency of flash flood forecasting in this area. These findings not only provide a theoretical basis for flood prevention and disaster mitigation in the Guanshan River Basin but also offer innovative approaches for flash flood forecasting in complex mountainous watersheds. The innovation of this study lies in its comprehensive consideration of multiple runoff generation mechanisms and its validation of the hybrid mode’s adaptability under different rainfall conditions through comparative analyses. Future research will further refine the runoff generation module by incorporating more detailed physical processes and parameterization methods, while exploring the coupled applications of hydrological and hydrodynamic models to enhance the model’s capability in simulating complex hydrological processes and provide deeper insights into flood evolution in small mountainous watersheds.