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Fitting flood frequency distributions using the annual maximum series and the peak over threshold approaches
Canadian Water Resources Journal ( IF 1.7 ) Pub Date : 2022-03-29 , DOI: 10.1080/07011784.2022.2052752
Daniel Caissie 1 , Gabriel Goguen 1 , Nassir El-Jabi 2 , Wafa Chouaib 1
Affiliation  

Abstract

Flood frequency plays an important role in the design of hydraulic structures as well as in the management of fisheries and aquatic resources. There are two types of flood frequency analyses, namely the annual maximum series (AMS) analysis and the partial duration series analysis (or peak over threshold, POT). The POT analysis consists of studying discharge data above a specific threshold (or truncation level), whereas the AMS method uses maximum annual discharge data. Both the AMS (generalized extreme value – GEV distribution) and POT (generalized Pareto – GP and exponential – Exp distributions) were used to calculate flood frequencies for four hydrometric stations within the Miramichi River basin of New Brunswick. A simple method was proposed for the selection of truncation levels, that is, values corresponding to 1, 1.5 and 2 flood counts per year. Considering multiple truncation levels in the POT analysis has the advantage of providing more results that are used to identify which level provides a better fit of the flood data. Both the GEV (AMS) and GP (POT) distributions best represented flood data within the Miramichi River whereas the Exp (POT) distribution did not fit well the data, especially for floods with high return periods (>25 years). Results showed the truncation level at a flood count of 1 (highest truncation level) for the POT method, generally provided a better fit of floods with high return periods (>25 years). Moreover, lower truncation levels tended to provide flood estimates with less uncertainties (lower coefficient of variation, as tested using a jackknife technique). Finally, results showed that both the AMS and POT methods are complementary in flood frequency analyses. The AMS is the more classic approach to flood frequency analyses; however, the POT provides a better characterization of floods (e.g. magnitude, duration and flood volume).



中文翻译:

使用年度最大序列和峰值超过阈值方法拟合洪水频率分布

摘要

洪水频率在水工建筑物的设计以及渔业和水生资源的管理中发挥着重要作用。洪水频率分析有两种类型,即年度最大序列(AMS)分析和部分持续时间序列分析(或峰值超过阈值,POT)。POT 分析包括研究高于特定阈值(或截断水平)的排放数据,而 AMS 方法使用最大年排放数据。AMS(广义极值 - GEV 分布)和 POT(广义 Pareto - GP 和指数 - Exp 分布)都用于计算新不伦瑞克省米拉米奇河流域内四个水文测量站的洪水频率。提出了一种简单的方法来选择截断级别,即对应于 1、1 的值。每年 5 次和 2 次洪水计数。在 POT 分析中考虑多个截断水平具有提供更多结果的优势,这些结果用于确定哪个水平可以更好地拟合洪水数据。GEV (AMS) 和 GP (POT) 分布最能代表 Miramichi 河内的洪水数据,而 Exp (POT) 分布不能很好地拟合数据,特别是对于高重现期(>25 年)的洪水。结果表明,对于 POT 方法,洪水计数为 1(最高截断水平)时的截断水平,通常更好地拟合高重现期(>25 年)的洪水。此外,较低的截断水平倾向于提供具有较少不确定性的洪水估算(较低的变异系数,如使用折刀技术测试的那样)。最后,结果表明,AMS 和 POT 方法在洪水频率分析中是互补的。AMS 是更经典的洪水频率分析方法;然而,POT 提供了更好的洪水特征(例如规模、持续时间和洪水量)。

更新日期:2022-03-29
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