洪积扇区域渠系工程设计洪水计算探究——以乌鲁木齐河分洪工程为例

通过对乌鲁木齐河分洪工程渠道沿线洪沟洪水的成因分析,对于山区河沟,采用水文比拟法计算出各河沟出山口处的洪水,对于出山口以下纯坡面区域,采用推理公式法计算其小流域暴雨洪水。根据沿线典型洪沟调查洪峰与推理公式法计算洪峰的拟合情况,率定出计算参数m为Ⅲ类,R=1.1、r1=0.76。对小东沟、乌什城沟出山口断面与渠线断面分别进行洪水调查,可知山区河沟出山口以后每公里河长洪峰衰减率为3.7%~3.9%。利用谷歌卫星地图结合现场调查,将分洪渠道沿线洪沟划分为各个相对独立的区域,对每一个区域分别计算出上游山区衰减至渠线断面的洪水和洪积扇区间洪水后,按照调查洪峰流量的比例将该区域洪峰总量分配到区域内与渠线相交的各个洪沟断面,基于工程安全性考虑,对于有汊流的洪沟,其最终设计洪水成果按加成20%进行处理。

The Design Flood Calculation of Channel Project in Alluvial Fan Area

The Urumqi River flood diversion project began on the right bank of the river and crossed the alluvial downstream in the south mountainous area and finally reached Chaiwopu Lake.Total length of the flood diversion channel is 32 kilometers.Through the analysis of the flood source along the channel,it was considered that the design flood of channel project was composed by flood in the upper reaches and the alluvial fan confluence.The hydrological analogy method was used to calculate the design flood at the mountain-pass.Besides the rational formula was adopted to calculate the rainstorm flood in small watersheds between the mountain-pass and the channel project.According to the fitting contrast between the survey flood and the calculated flood,the parameters were determined as follows:m was class Ⅲ,and R =1.1,and r1 =0.76.Based on the flood investigation at the mountain-pass and the channel section in Xiaodonggou and Wushichenggou respectively,the flood attenuation rate per kilometer along the river course was 3.7 ％ to 3.9 ％.The ditches along the channel could be divided into separate regions using Google satellite map,and the flood in the mountainous area and the rainstorm flood in the alluvial fan could be calculated for each region.According to the proportion of flood suvey,the total flood in every defined contolling area can be allocated to each flood ditch.Considering the shunt effect,the design flood was increased 20％ for the project safety.