基于广义极值分布和Metropolis-Hastings抽样算法的贝叶斯MCMC洪水频率分析方法

广义极值（GEV）分布是国内外洪水频率分析建模中广泛应用的一种概率分布。本文将水文频率分布线型的未知参数看作随机变量，通过基于Metropolis-Hastings抽样算法的贝叶斯MCMC方法估计GEV分布参数和设计时段洪量的后验分布，并据此进行极值洪水的频率分析。汉江流域丹江口水库年最大1日（3日、5日、7日）洪量频率分析的结果表明了本方法的有效性和实用性。主要结论包括：基于Metropolis-Hastings抽样的MCMC模拟在GEV分布参数的贝叶斯估计计算中行之有效；由于利用了与似然函数渐近性质无关的先验信息，贝叶斯估计方法得到的高分位数设计洪量的后验分布比经典统计方法得到的设计洪量能包含更多的信息，从而能表达由于参数不确定性而引起的预测不确定性。该方法能显著地通过分位数图、PPCC法、均方根误差法、K-S法等多种拟合优度检验方法，拟合效果不亚于其他常用的经典统计方法。     

Flood Hydrology and Geomorphology of Monsoon-dominated Rivers: The Indian Peninsula

ABSTRACT

The rivers of the southern part of the Indian Peninsula are monsoonal in nature and the hydrological characteristics of these rivers djffer markedly from those of Himalayan rivers. The rivers are subjected to severe floods during the monsoon season. In the last few decades, several large-magnitude floods (peak floods between 10,000 and 80,000 m³/s) have been recorded. In general, floods caused by precipitation from Bay of Bengal depressions include the peak flood of record. Analyses of the systematic, historical, and paleoflood records indicate that, in recent decades, the frequency of high-magnitude floods has increased significantly. Hydraulic estimates reveal that high flows are capable of bedrock erosion and transportation of coarse material.

Such large floods are important, not only from the standpoint of geomorphic work, but also in terms of social impact. Floods in the peninsular region are responsible for colossal loss of human life, crops, and property. In recent years, various measures offlood control and management have been adopted. However, flooding in such large rivers profoundly challenges flood-hazard management, because of the inadequacy of conventional data and high spatio-temporal variability of floods. To understand flood hazards and environmental change it is imperative that engineers and hydrologists utilize historical and paleoflood records to improve risk analyses as well as to estimate probable maximum flood on rivers such as these in a highly flood-prone region.     

天峨水文站历史洪水首项经验频率置信区间估算

历史特大洪水加入样本系列，对提高设计洪水精度起着关键作用。但由于特大洪水的稀遇性，以及随着实测系列的延长，其经验频率又具有不确定性，给频率曲线的外延带来任意性。采用引入对首项顺序统计量置信区间估计的方法，对首位历史洪水经验频率置信区间进行估算，指导频率曲线的适点配线，对设计洪水和设计暴雨分析计算工作具有一定的实用意义。     

A customised approach to determining the geomorphic effectiveness of small flood events in a regulated river

The construction of dams significantly alters flow and sediment regimes with subsequent deleterious effects on the morphological and ecological character of rivers. Effective experimental floods can ameliorate the downstream geomorphic impacts of dams. The traditional view is that large floods are required to perform effective geomorphic work, and the geomorphic outcomes of small floods are often overlooked. Many river restoration frameworks do not consider small floods. Yet, there is evidence that the hydrological characteristics that ameliorate specific geomorphic impacts in a river are unique to each river, and a customised approach to setting the right mix of floods (including small experimental floods) is needed. In this study, we modify an existing flood effectiveness model developed for large floods, for determining the geomorphic effectiveness of small floods in a highly regulated Australian river. Two flood classes were added to the model (medium peak stream power and moderate total energy expenditure), and the flood power characteristics were rescaled to reflect the relative difference in the magnitude of the small floods and the magnitude of the geomorphic work performed. Using a step‐wise approach, this customised model determined the geomorphic effectiveness of small floods. The best flood for ameliorating the geomorphic impacts of flow regulation had medium to long duration (10 to 51 days), high peak unit stream power (77 to 123 Wm^?2) and moderate to large total energy expenditure (78,600 to 342,320 × 10³ J). This approach to determining flood effectiveness for small floods is applicable to other geomorphically impacted river channels downstream of dams and can be used to inform experimental flood releases for geomorphic outcomes.     

基于蒙特卡罗法的土石坝洪水漫顶风险率计算及其敏感性分析

为了减少土石坝因洪水漫顶造成溃坝所带来的损失,详细介绍了计算土石坝洪水漫顶风险率的蒙特卡罗法模型,分析了影响土石坝洪水漫顶的主要因素为洪水、风浪、水库运行调度方式和水库特性。针对这些因素进行洪水漫顶风险率的敏感性分析,并以南方某土石坝为例进行了实例研究。结果表明:洪峰流量均值和变差系数以及最大风速的均值对土石坝洪水漫顶风险率的影响较大,洪峰流量的偏态系数和风速的均方差的影响较小;水库自身特性及洪水到来前的水库初始水位的影响也比较大。该实例计算得到的洪水漫顶风险率经与相关工程实例分析计算成果比较,表明采用蒙特卡罗法计算洪水漫顶风险率是可信的。     

江口水电站设计洪水分析研究

在分析芙蓉江流暴雨的洪水特性的基础上，采用多种方法插补展延了洪水资源系列，并充分利用历史洪水调查资料，使设计洪水分析计算采用的资料具有一定的代表性，可靠性，其中坝堤百年一遇设计洪水洪峰流量为12000m^3/s,72h洪量为10.2亿m^3，对江口水电站设计洪水成果，通过与上下游，干支流各站的设计洪水参数及与长江流域的部分大中型水利水电工程设计水成果比较，进行了合理性分析。     

2016年7月长江区域性洪水重现期分析

受超强厄尔尼诺事件影响,2016年6～7月西太平洋副热带高压偏强偏西,导致长江梅雨期降雨异常偏多、暴雨频发,中下游地区发生了3场区域性大洪水。通过干支流控制性水文站和水利工程的观测资料,还原出天然来水量过程,统计了洪峰流量和不同时段洪量,结合现有历史洪水资料和工程设计成果,分析了2016年洪水特征和重现期。分析结果表明,宜昌以下干流河段均出现超警戒水位,洪水重现期在5～10 a之间;清江、资水、水阳江、鄂东北诸支流等发生特大洪水,水位、流量超过历史最高纪录,重现期为100～200 a一遇;修水、饶河等发生一般洪水,重现期在20 a一遇以下。     

A Versatile Flood Frequency Methodology

ABSTRACT

Many observed annual flood series exhibit reverse curvatures when plotted on lognormal probability paper. The occurrence of these curvatures may be attributed to seasonal variation in flood-producing storm types, relative dominance of within-the-channel or floodplain flow, and variability in antecedent soil moisture and cover conditions. A mixed distribution model is needed to analyze such flood series because of the mixed population of floods. A versatile flood frequency methodology has been developed which considers the probability distribution of an observed flood series as a mixture of the probabilities of two lognormal distributions. Objective detection and modification of any outliers and inliers in an observed flood series in as integral part of the versatile flood frequency methodology. Analyses of about 600 flood series in the USA and other countries in the world show the versatility and superiority of the proposed methodology for satisfactory estimation of design floods for various recurrence intervals.     

对1995年长江中下游洪水的认识

１９９５年６、７月间长江中下游干流及洞庭，鄱阳两湖地区发生了较大洪水，加上河湖槽蓄量的变化，中下游干流个别站和两湖的一些支流控制站出现了超历史最高洪水位，作者从峰现时间，洪水组成，洪水位和各河段分布洪量，洪水水面线，水位流量关系等方面对１９９５年长江中下游洪水的特性进行了分析，认为１９９５年长江洪水属于中下游型洪水，大通站最大洪水流量为建国以来仅次于１９５４的较大洪水流量。     

长江上游流域暴雨洪水相似性判别指标研究

暴雨洪水发生演化的各个阶段之间存在一定的关联性和规律性。以长江上游流域为研究对象,将暴雨洪水指标分为降雨、洪水、时间、雨洪关系、水库、形状和初始指标7大类,共67个指标。通过整理暴雨历史洪水资料,摘录暴雨洪水过程和计算暴雨洪水特征值,结合洪量相似度、洪峰相似度、形状相似度和灰色关联度4种相似性评价方法,优选出降水量、降水历时、起涨流量和洪水涨率4个指标作为相似洪水判别指标。以113场三峡入库洪水为样本进行相似性检验,基于几场典型洪水特征值寻找的历史相似洪水之间的相似度较高,确定性系数都达到了0.9以上。结果表明,降水量、降水历时、起涨流量和洪水涨率4个指标作为相似洪水判别指标,对指导实时洪水预报具有较高的参考价值。研究成果在三峡水库以上长江上游流域进行了试验应用,在寻找历史相似洪水方面具有较好的效果。     

设计洪水在防洪计算中的误区

在防洪计算中,设计洪水的可靠性直接影响着待建工程的规模大小、安全程度和浪费状况。本文主要阐述了影响设计洪水计算成果的几种误区：一是过多使用人造插补延长资料系列的误区;二是特大洪水插补越多越好的误区;三是面积和河长水文比拟法的选用的误区;四是无连续大洪水发生,设计洪水稳定不变的误区等。并通过对陕西省泾河上的张家山和桃园水文站流量系列进行实例分析,分别验证这四种误区的影响。     

黄河中游粗泥沙集中来源区产沙规律综述

在前人研究的基础上分析总结了该区特有的暴雨洪水产沙规律：暴雨是侵蚀产沙的主要动力，暴雨、洪水、泥沙之间存在着必然的关系；洪水发生时间集中，峰高量大，暴涨暴落，对黄河中游大洪峰的形成具有决定性影响；侵蚀产沙强烈而粗泥沙集中，输沙能力强，洪水含沙量高，是黄河粗泥沙的集中来源地；河龙区间特别是粗泥沙集中来源区频繁或连续的暴雨洪水对黄河输沙有重要影响；随着治理水平的提高，区域洪水有减小趋势，但泥沙量变化不明显，大部分支流的洪峰流量、洪水含水量反应不敏感，说明一般规模和水平的治理工程还不能有效控制区域大洪水特别是特大洪水的泥沙。     

基于最大熵原理方法的洪水预报误差分布研究

采用最大熵原理(POME)方法，对我国湿润和半湿润地区部分典型水库的洪水预报误差分布规律进行了研究。通过建立洪水预报误差分布的最大熵模型，计算出9座典型水库洪水预报的净雨相对误差、洪峰流量相对误差和峰现时间预报误差的概率密度函数，并将其概率密度函数曲线与正态分布曲线进行比较。结果表明，我国湿润和半湿润地区的洪水预报误差近似服从正态分布，且采用POME方法计算洪水预报误差分布是可行的。     

1998年长江、嫩江大水给我们的启示和反思

对长江流域１９５４年与１９９８年两次洪灾作详细的比较，分析了长江流域发生特大洪水的主要原因．结合历史及１９９８年抗洪的经验教训，对长江、嫩江、松花江流域今后的治理方略提出建设性意见，并对海河、黄河防洪问题作深入的探讨．文末还对多年来对水利投入和产出的错误理解作出合理的解释．     

贺江流域特大暴雨洪水特性分析

贺江流域"1994.7","2002.7"相继发生了特大洪水,给沿江两岸造成了严重的洪涝灾害.对这两场暴雨洪水的成因、雨洪特点、暴雨洪水过程、洪水组成、重要水利工程排洪等进行分析,探索出贺江流域特大洪水的成因及特性,为该流域水利工程建设和防洪规划提供科学的依据.     

潇河大坝洪水分析中对历史调查洪水的考虑

本文通过采用潇河大坝长短系列及对历史调查洪水的不同处理方式，进行潇河大坝的洪水分析计算，并对结果进行比较，提出了在设计洪水分析计算中对历史洪水考虑方式的意见和理由。     

1999年长江洪水及几点认识

Following the basin wide heavy flood on Changjiang River in 1998, a si gnificant flood occurred in 1999. Comparative analysis of both floods in terms of flows and flooding situations shows that both floods had one common feature, that is, the flood stages were fairly high. But they differed greatly at the sa me time, that is, the 1998 flood was a basin wide heavy one while the 1999 flood was a significant local one. At Yichang station there occurred eight flood pea ks in 1998, while in 1999 only three peaks took place. The maximum peak dischar ge at this station in 1999 was 57 600 cubic meters per second, which was smaller than that in 1998. The maximum flood-volume in 30 d of the 1998 flood at this s t ation equaled that in 1954, when an extraordinary heavy flood happened on the River, while the maximum flood-volume in 30 d in 1999 was 25.8 billion cubic me t ers per second smaller than the 1998 one. It is seen that inflow floods from th e upstream Changjiang River (above Yichang) in 1999 were not so big. Comparison of flood volumes in longer period shows that the 1999 flood was relatively conc entrated while the 1998 one had lasted longer duration. Analysis shows that flo oding situations in both years differed significantly in terms of the flood volu mes diverted from river channels due to dyke breaches and collapses, the cases o f polder embankment collapses, the areas of inundated cultivated land and the nu mbers of dangerous events for hydraulic structures. These differences had been resulted from the different properties of both floods and the dyke strengthening efforts made after the 1998 flood. It is seen that flood control engineering c onstructions initiated in the days following the 1998 flood have played an impor tant role in fighting the 1999 flood.     

三里坪水利枢纽工程设计洪水复核分析

南河流域洪水特性受台风雨影响,表现为洪高量大,汇流快。为了对三里坪枢纽工程验收提供设计洪水复核成果,通过对坝址附近控制站—台口（二）水文站多年实测资料分析,并进行历史洪水调查,结合历史洪水与实测洪水组成不连续系列进行频率分析,得出坝址设计洪水成果,对原有初步设计成果加以复核。复核结论认为,依据台口（二） 站计算的设计洪水成果可作为三里坪水库的设计依据。其分析计算方法可供类似工程区域设计洪水计算参考。     

At-Site Flood Frequency Analysis Coupled with Multiparameter Probability Distributions

The proper design of hydraulic structures as well as river basin management are directly dependent on adequate estimates of maximum streamflow, preferably obtained from long historical series. However, the scarce hydrological monitoring, recurrent in developing countries and the need for estimates associated with high return periods (RPs) have led to the use of estimation methods based statistical procedures, such as at-site flood frequency analysis. This study presents a framework for at-site flood frequency analysis coupled with multiparameter probability distribution functions (PDFs) (GEV, LN3, PE3, GLO, GPA, KAP and WAK), in which all the statistical procedures are derived from L-moments, in order to investigate the applicability of these PDFs in comparison to those of 2-parameters (EV1, LN2 and Gamma). The modeling framework was evaluated considering 106 maximum annual streamflow (MAS) series for the Rio Grande do Sul State - Brazil. PDFs’ goodness-of-fit was studied in accordance with the Anderson-Darling test. It can be concluded that: i) the multiparameter distributions, especially KAP and WAK, had performance superior to the traditional 2-parameter distributions, providing a greater number of historical series better adjusted by such multiparameter PDFs; ii) shorter series were usually better represented by GEV when compared to the other PDFs, which is an important characteristic when long historical series are not frequently available; and iii) the quantile estimates derived from multiparameter PDFs presented lower Relative Absolute Error, thus emphasizing the importance of using such PDFs in water resources management and engineering projects.     

Uncertainty evaluation of design rainfall for urban flood risk analysis

A reliable and long dataset describing urban flood locations, volumes and depths would be an ideal prerequisite for assessing flood frequency distributions. However, data are often piecemeal and long-term hydraulic modelling is often adopted to estimate floods from historical rainfall series. Long-term modelling approaches are time- and resource-consuming, and synthetically designed rainfalls are often used to estimate flood frequencies. The present paper aims to assess the uncertainty of such an approach and for suggesting improvements in the definition of synthetic rainfall data for flooding frequency analysis. According to this aim, a multivariate statistical analysis based on a copula method was applied to rainfall features (total depth, duration and maximum intensity) to generate synthetic rainfalls that are more consistent with historical events. The procedure was applied to a real case study, and the results were compared with those obtained by simulating other typical synthetic rainfall events linked to intensity-duration-frequency (IDF) curves. The copula-based multi-variate analysis is more robust and adapts well to experimental flood locations even if it is more complex and time-consuming. This study demonstrates that statistical correlations amongst rainfall frequency, duration, volume and peak intensity can partially explain the weak reliability of flood-frequency analyses based on synthetic rainfall events.