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三峡区间是长江上游暴雨多发区,其洪水是三峡库区洪水的重要组成部分.长江流域1954年大洪水期间,库区30天最大洪量中区间洪水的比例达13.2%,而区间特殊的地形条件造成区间的众多支流坡度大且流程短,汇流迅速,因此有可能对库区洪峰产生更大影响.目前区间水文站点较少,不能为评估区间入流对库区洪峰的影响提供足够的水文资料.文章选取1956~2000年间的880场洪水为研究对象,在三峡库区长江干流基于HEC-RAS建立了洪水演进数值计算模型,通过对比不考虑侧向入流的洪水演进计算所得洪水过程线和实测洪水过程线,定量识别区间入流对三峡库区洪峰的贡献量和贡献率,以及对峰现时间的影响,并统计分析不同量级洪峰样本中区间入流影响的变异性.采用4套不同研究机构的糙率参数,对比不同糙率参数方案计算结果的差异,分析糙率参数的不确定性对研究结果的影响.研究发现,区间入流对库区洪峰的平均贡献量为3524m3/s,平均贡献率为15.9%,不同场次洪水之间的变异性较大.其中对大于50000m3/s洪峰的贡献量平均为12000m3/s,最大可接近25000m3/s;贡献率平均为20%,最大接近50%.在统计意义上,较大洪峰中区间入流的贡献量及其变异性较大,贡献率及其变异性略大,区间入流贡献率大的洪水场次出现频率较高;区间入流可改变库区洪水过程线形状,使洪峰提前出现,对峰现时间的影响及其变异性随贡献率的增大而增大.以上结果表明三峡区间入流对库区较大量级的洪水过程有显著影响,为保证三峡大坝及其下游的度汛安全,需要采用更为先进的洪水预报技术延长区间洪水预报的预见期,提高预报精度.
The Three Gorges section is a heavy rainy area in the upper reaches of the Yangtze River and its flood is an important part of the flood in the Three Gorges reservoir area. During the 1954 flood season in the Yangtze River Basin, the proportion of flooding in the 30-day maximum flood in the reservoir area reached 13.2% while the special terrain As a result, there are many hydrological stations in the reservoir area that are less likely to provide adequate hydrological data for the impact of the assessment interval on the flood peak in the reservoir area. In this paper, 880 floods from 1956 to 2000 are selected as the research object. Based on HEC-RAS, a numerical model of flood evolution is established in the mainstream of the Yangtze River in the Three Gorges Reservoir Area. By comparing the flood process curve with the measured flood without considering the lateral inflow, Process line and quantitative identification of the inflow to the Three Gorges reservoir peak flood contribution and contribution rate, as well as the impact on the peak time, and statistical analysis of different magnitudes of flood peak sample inflow influence of variability.Using four different research institutions Roughness parameters were compared with those of different roughness parameters to calculate the differences between the results of the study and the uncertainty of roughness parameters The study found that the average contribution of flood inflow to the reservoir area is 3524m3 / s and the average contribution rate is 15.9%, and the variability between different floods is larger, of which the average contribution to the flood peak greater than 50000m3 / s is 12000m3 / s, the maximum is close to 25000m3 / s, the average contribution rate is 20% and the maximum is close to 50% .In a statistical sense, the contributions and variability of inflows in larger flood peak are larger, and the contribution rate and variability are slightly Large and inter-interval inflows have a high frequency of occurrence. Flood influx can change the shape of the flood course in the reservoir area and make the flood peak ahead of time. The impact on peak time and its variability increase with the contribution rate The above results show that the inflow of the Three Gorges Project has a significant impact on the flood process of larger magnitude in the reservoir area. In order to ensure the flood control safety of the Three Gorges Dam and its downstream, more advanced flood forecasting techniques are needed to extend the forecast period of interval flood forecasting, Improve forecast accuracy.