Characteristics And Prevention Of Glacial Lake Outburst Flood In Yarkant River

For many years,Glacial Lake Outburst Floods often occur in the Yarkant River Basin,which bring flood disasters and risks to the lower reaches of the basin.To prevent the GLOF better in the new period,based on the existing technical means and monitoring data,combined with the reality of flood prevention in the river basin,and further analyzed and understood the variation characteristics of the GLOF,around the relevant functions of the water conservancy department after the institutional reform,the study of flood prevention is carried out to further improve the ability and level of flood prevention in the lower reaches of the basin,and to provide corresponding technical supports and policy suggestions for river basin and local management departments in the new era.The main conclusions of this research were exhibited as follows:(1)Inter-decadal analysis,frequency analysis,cumulative anomaly analysis,Mann-Kendall test and rescaled range analysis(R/S)were simultaneously conducted in analyzing the characteristics of the GLOF changes.In the Yarkant River,presented the pattern of"frequent-intermittent" alternation in inter-decadal scales during twenty years,along with the jump of the inter-decadal mean values.In month distribution,GLOF accompanied with the largest flood in a year mainly occurred in August and September.1961 and 1999 were the variation years in annual maximum peak discharge and outburst flood peak discharge.The annual maximum peak discharge and the peak discharge of GLOF were correspondingly emerged with decreased tendencies from 1959 to 2015.The Hurst Indexes were less than 0.5 in Kuluke Langan and Kaqun Hydrological Stations,exhibiting reverse sustainability.In the future,the GLOF of more than the largest magnitude in history may occur in the basin.(2)The correlation formula of flood peak discharge of GLOF in hydrological station is obtained by using the method of correlation analysis.Based on the measured flood peak discharge data of hydrological station,the initial flood volume of GLOF can be estimated.The fitting correlation of GLOF peak discharge in Kuluke Langan station can also provide corresponding data reference for the prevention and operation of the flood in Altash Reservoir.When issuing an operation order to the reservoir management department,the flood prevention department may make a judgment in advance according to the flood volume of GLOF and draw up a preliminary plan for the discharge of the reservoir.(3)After reservoir regulation and storage of the GLOFs under the different flood standards occurred in the upper reaches in the basin,the reservoir discharge is divided into flood control discharge,disaster discharge and major disaster discharge.The discharge of reservoir operation does not exceed the safe discharge of 1750m3/s of downstream river,which is the flood control flow;the discharge of reservoir is between 1750m3/s and 4214m3/s,which is the disaster flow;and the discharge of reservoir is more than 4214m3/s,which is the major disaster flow.The Flood Area model is used to simulate the types of disaster flow and major disaster flow after reservoir regulation and storage,respectively,with low-scene and high-scene.The flood inundation risk range of the simulated irrigation area in the low scene is small;the flood inundation risk range of the simulated irrigation area in the high scene is near the river section in the plain area,which is mainly distributed in the low-lying areas and on both sides of the Yiganqi ferry and below the river.The inundation risk shows a trend of increasing gradually from south to north.(4)Take the combination of engineering and non-engineering measures to implement comprehensive risk prevention of the GLOF.In terms of engineering measures,it is mainly based on the "combination of reservoir and dike" project defense,supplemented by the joint engineering defense of short-term flood diversion and flood storage,as well as measures such as temporarily exceeding the guaranteed water level operation of the dike and heightening the sub-dike;if it exceeds the defense capacity of the dike,then bear the appropriate risk of flood inundation.Further measures in non-engineering can be conducted on construction of organization system,completion of various plans,establishment of expert databases,improvement of construction in information capability,application in new flood control and emergency technology,implement of flood safety and advancement in socialized services,etc.