张家界地区溇水流域洪水特征分析

Analysis of flood characteristics in Loushui basin of Zhangjiajie region

以张家界地区主要水系溇水流域为研究对象,利用长潭河站1966年以来有记录的水文泥沙资料（25 a）,分析溇水流域不同阶段洪水发生频率、洪峰规模、洪水输沙能力及水沙关系特征的变化规律.通过有序聚类方法将溇水流域洪水变化过程划分为1966-1969年、1970-1985年和2007-2011年3个阶段.研究结果表明：溇水流域以夏季洪水为主,发生频率约占56％.25 a间,洪峰流量主要集中在500～1 000m3/s,大于1 000m3/s的洪水发生频率在不同时段分布规律不尽相同,最高洪峰流量可达到7 000m3/s.洪水对溇水流域输沙量的贡献远大于水量的贡献,最大洪水事件对溇水流域输沙过程起主导作用,其最大贡献率可达73％（1966年）.3个阶段“流量-含沙量”呈幂函数关系,其系数变化特征表明溇水流域洪水输沙来源相对不充足.1970-1985年间洪水输沙能量有所增加,而2007年后输沙能量有所降低.不同阶段“流量-含沙量”滞后环特征变化在一定程度上表明溇水流域悬移质榆沙来源从河道向坡面或上游较远的地方转移.

Loushui basin of Zhangjiajie region was selected as study area.Based on available hydrology data （since 1966） of 25 years,changes of flood characteristics were analyzed,including the changes of flood frequency,flood scale,flood transportability and relationship between water and suspended sediment concentration.By the application of sequential cluster,the time series of flood water and sediment characteristics can be generally divided into three periods,i.e.1966-1969,1970-1985 and 2007-2011.The results showed that 56% floods happened in summer.Most maximum flood discharges were in the range of 500～ 1 000 m3/s during the study period.When the maximum flood discharge is larger than 1 000 m3/s,the distributions of floods were different in three stages,and the maximum flood discharge can reach 7 000 m3/s.The contribution of flood to the total annual sediment load in Loushui basin was much higher than the contribution of flood to runoff.The transportation of suspended sediment was controlled by the maximum flood event,with the maximum contribution reaching approximately at 73% in 1966.Power function can be used to describe the relationship between flood discharge and suspended sediment concentration.The changes of the parameters of power functions indicated the insufficient sediment availability of floods in Loushui basin.There was an increase in flood sediment transport energy during the period of 1966-1985,with a sharp decrease after 2007.To some extent,the changes of hysteresis loops for flood discharge and suspended sediment concentration indicated the changing of sediment sources from sediment in channel bed/bank to materials on slopes or upper reaches in Loushui basin.