2012年洪水对黄河内蒙古段冲淤影响

Effects of the coarse sediment movement in the flood on Inner Mongolia Reach of Yellow River in 2012

2012年洪水是内蒙古河段1989年以来历时最长、洪峰流量最大的洪水过程。为了解粗泥沙对黄河内蒙古段河床冲淤变化的影响,依据宽河谷河段巴彦高勒、三湖河口和头道拐水文站实测资料,分析了内蒙古河道2012年洪水水沙特征,通过计算推移质输沙量和比较断面河底变化,探讨了粗泥沙对河底调整的影响。结果表明:2012年洪水造成粗泥沙在上游段冲刷、下游段淤积;固定低水位下过流断面存在涨冲落淤的规律;洪水过后,巴彦高勒和三湖河口低水位面积分别扩大了19 m^2和29 m^2,头道拐减小约100 m^2。由于粗泥沙排沙不平衡,底部河床的真正高程并没有降低,防洪风险依然存在。

Coarse sediment movement in rivers is one of the key factors in causing changes in channel characteristics.The duration of the 2012 flood in the Inner Mongolia Reach of the Yellow River（ IMYR） was the longest and the peak discharge was the biggest since 1989. The aim of this study was to investigate the impact of the movement of coarse sediment during the 2012 flood on the riverbed of IMYR,a coarse sand reach. The wide valley reach of IMYR is bounded by the Bayangaole,Sanhuhekou and Toudaoguai gauging stations from upstream to downstream. The coarse sand in the channel is one of the most important factors impacting riverbed erosion and deposition. Using real observational data,we analyzed the water and sediment characteristics of IMYR during the 2012 flood. By calculating sediment discharge of the bed load and comparing the river bottom of the fixed sections during the flood,this paper assesses the effect of the movement of coarse sediment on the river bottom adjustment. The results show that,（1） the coarse sediment was scoured in the upstream part of the IMYR and deposited downstream during the flood in 2012;（2） the open area beneath the fixed low water level followed the rule of scouring during the flood rising period and deposition during the flood falling period;（3） the open area under the low water at Bayangaole and Sanhuhekou gauging station expanded by 19 m^2 and 29 m^2 respectively,while the same at Toudaoguai gauging station decreased by approximately100 m^2. Owing to the imbalance of coarse sediment ejection after the flood,the actual elevation of the riverbed bottom did not get lower,and the flood risk remains at a similar level.