长江中游黄州河段采砂影响分析

Impact analysis of sand mining of Huangzhou reach in middle Yangtze River

河道采砂等人类活动对河道演变的影响是河流动力学研究的一个重要课题。以长江黄州河段为例,在实测水沙系列的基础上,采用平面二维水沙数学模型研究了不同流量级下工程河段采砂后水位、流速和汊道分流比等变化规律,并模拟了不同典型年水沙条件下洲滩河段演变过程和采砂区冲淤特性。研究结果表明,在不同流量条件下,随着流量的增加,水位和流速变化幅度有所减小、影响程度降低;分流比对平滩流量反应更加敏感,平滩流量条件下分流比有明显增加;三峡水库蓄水运行后,在不同典型水文年条件下,随着洲滩的冲刷后退加剧,布置在洲尾的采砂区泥沙回淤明显。

The impacts caused by the human activities such as sand mining upon the fluvial process in a river are the important problems to study in the river dynamics field. The Huangzhou reach in the middle Yangtze River was selected as a case study. Based on the data of the measured water and sediment series in the river basin,a 2-D mathematical model for water and sediment was established. The changing rules of the water level,flow velocities and water diversion ratio were analyzed,and the fluvial process in study area was simulated in three representative hydrological years. The simulated results show that the variation range of the water level and flow velocities will decrease with the increase of the flow discharge; moreover,the water diversion ratio is much more sensitive to the bankfull discharge,thus there will be an obvious increase in the water diversion ratio when the river reaches the bankfull discharge. Although there is a decrease in the sediment concentration after the operation of the Three Gorges reservoir,sand redeposition occurs obviously around the mining area with natural scouring and retrogradation around the riffle. The research results can provide a scientific reference for the feasibility study and planning of the sand mining in the similar rivers.