糙率对感潮河段水位预报的影响

Effect of Roughness on Stage Forecasting in Tidal Reach

感潮河段洪水受上游洪水和下游潮水的共同作用,且河道断面复杂,这些因素加剧了糙率取值的难度。本文通过糙率影响试验,分析了糙率改变对感潮河段计算水位的影响。在具有明显漫滩的断面,将糙率取值分为漫滩糙率和主槽糙率后再进行水位计算。试验结果表明,糙率值的改变对计算水位影响较大,且对感潮河段洪水过程的不同阶段影响程度不同;漫滩糙率的改变对漫滩洪水位影响很大,主槽糙率的改变对低水位影响较大。

River roughness is a sensitive parameter in the hydrodynamic model, and its determination is the key of numerical modeling. Flood in tidal reach is contributed by both flood wave from upstream and tidal wave from downstream, moreover cross-sections of tidal river channels are compound, which make roughness calibration more difficult. Four roughness tests were established to analyze the effect of roughness on tidal reach stage forecasting in this study. In the cross-sections with obvious floodplains, roughness was divided into main channel roughness and floodplain roughness. The results show that stage hydrographs change with the variation in roughness, and this effect is different in different parts of the hydrograph. In addition, floodplain roughness has great effect on the stage of overland flow, and main channel roughness affects low stage forecasting.