基于风险的非一致性设计洪水及其不确定性研究

研究非一致性条件下的设计洪水对水利工程规划设计、防洪决策等具有重要意义,当今国内外研究方法主要集中于时变矩法,然而,该方法对于某一设计频率推求出的每年一个设计值很难用于实际。水利工程设计需要量化两方面的基础信息,工程设计使用年限及设计使用年限内水文风险。本文尝试将水文风险的概念引入到非一致性条件下设计洪水研究当中,其中选取更具物理意义的气象因子作为洪水频率分析的协变量,进一步结合大气环流模型(General Circulation Model,GCM)输出数据的统计降尺度结果推求特定设计使用年限内某一水文风险下的设计洪水,并与传统以时间为协变量的情况进行比较。选取渭河流域洪水序列作为实例研究。结果表明:两种协变量情况下非一致性设计洪水及其95%置信区间相比于一致性假设情况存在明显差别,并且以气象因子为协变量的非一致性设计结果相比于时间为协变量更为合理。本文方法所得设计结果可为水利工程规划设计及防洪决策提供一定参考依据。

Risk-based nonstationary design flood and uncertainty analysis

Design flood and its uncertainty analysis under nonstationary conditions is critical consideration in the planning and design of hydraulic structures and making flood control decisions. The time-varying moment method is widely applied, but a measure of design flood varying from one year to the next derived from the time-varying moment method is hard to be applied to practical application. The basic information needed for engineering design should consist of the design life period and the hydrological risk of a flood event occurring during the design life period. This paper is aimed to improve the characterization of nonstationary design flood and its uncertainty under the concept of hydrological risk by employing meteorological covariates in the nonstationary frequency analysis. The advantage of the method is that the downscaled meteorological variables from the General Circulation Model (GCM) can be used to calculate the nonstationary statistical parameters and exceedance probabilities for the design life period and thus the corresponding design flood quantile. The method of using time as the only covariate was also employed for comparison. Both methods were applied to the annual maximum daily streamflow series of the Wei River,China. It is demonstrated that the nonstationary design flood results of both covariate situations were significantly different from the stationary case. The nonstationary design flood result using temperature and precipitation as covariates was found more reasonable and advisable than that of the case using time as covariate. It is concluded that the nonstationary design result of this study can be valuable reference for the planning and design of hydraulic structures and making flood control decisions.