基于典型次洪泥沙动力学过程的岔巴沟流域水沙关系分析

为准确把握岔巴沟流域径流泥沙变化趋势并分析其原因,以岔巴沟流域1970—2016年98场洪水输沙过程为研究对象,通过分析不同年代次洪输沙量,阐明了次洪水输沙动力学过程。结果表明:岔巴沟流域近50 a来次洪输沙滞回曲线模式主要表现为顺时针型、逆时针型、8字型、复杂型4种,4种模式中逆时针型所占比例和次洪输沙量最大,顺时针型所占比例最小,但平均洪峰流量和平均输沙峰值最高,复杂型洪水平均持续时间最长。不同年代次洪输沙频率表现为1980—1989年间洪水输沙滞回曲线以逆时针型为主,其次为复杂型洪水,2006年以来逆时针型和复杂型洪水数量大幅减少,8字型洪水数量增多; 出现这种现象可能是由于岔巴沟流域自20世纪70年代以来开展小流域综合治理,各种水土保持措施在1970—1989年间产生较强的作用,但2000年后,由于长期使用后产生淤满和损坏等状况,效力逐渐降低,对岔巴沟流域整体的水沙输移模式产生影响。

Runoff and Sediment Relationship in Chabagou Catchment Based on Sediment Dynamics in Typical Single Flood Event

To obtain the change trends of runoff and sediment in the Chabagou catchment, we expound the sediment transport dynamics in single flood event by analyzing the sediment load in 98 flood events during 1970-2016. Results show that the hysteresis curve patterns(denoted by the C-Q relation) of flood and sediment transport in the Chabagou catchment over the past five decades mainly include four types: clockwise, counterclockwise, 8-shaped, and complex. Among the four modes, the counterclockwise type has the largest proportion and the largest amount of sediment transported by flood, while the clockwise type has the smallest proportion but the highest average peak flow and highest average sediment peak, whereas complex pattern has the longest average duration. In temporal scale, the hysteresis curve of flood and sediment transport in 1980-1989 is mainly counterclockwise, followed by complex pattern. Since 2006, the number of counterclockwise pattern flood and complex pattern flood has decreased significantly, while the number of 8-shaped pattern has increased. This phenomenon can be accounted for the following facts: comprehensive management of small watersheds has been carried out since the 1970s, and various soil and water conservation measures have had strong effects in 1970-1989; however, after 2000, due to depositions and damages after long-term use, the effectiveness gradually reduced, affecting the overall water and sediment transport mode in the Chabagou catchment.