Flood Frequency Analysis of Interconnected Rivers by Copulas
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Flood Frequency Analysis of Interconnected Rivers by Copulas Esmaeel Dodangeh 1 & Vijay P. Singh 2 & Binh Thai Pham 3 & Jiabo Yin 4 & Guang Yang 5 & Amirhosein Mosavi 6,7 Received: 21 December 2019 / Accepted: 21 July 2020/ # Springer Nature B.V. 2020
Abstract
Flood frequency analysis (FFA) considering the confluence of interconnected rivers is important for hydraulic structures (such as dams or diversions) design, but it has received little attention. This study develops a copula-based method for FFA and quantile estimation considering the confluence of two interconnected rivers, along with the uncertainty estimation by a nonparametric bootstrapping algorithm. Flood probability distribution and return periods are estimated for the two rivers by mapping from bivariate to univariate peak flow quantile estimation. The methodology is applied to the case study of Qezel Ozan and Shahrud Rivers which merge to one of the largest reservoir dams in Iran: Sefidrud (Manjil) dam. According to the results from Peak flow records from Gilvan station (GPF) at Qezel Ozan River and from Loshan station (LCF) at Shahrud River, Gaussian copula with Weibull and gamma margins fits best. Also, it shows that some peak flow quantiles with the same magnitudes have a different probability of occurrences at the confluence of the rivers, and the bivariate estimation uncertainty usually plays an important role in FFA. These findings suggest the use of bivariate instead of univariate distributions to the peak flows at the confluence of interconnected rivers, in which the sampling uncertainty should be considered. Keywords Interconnected rivers . Copulas . Gaussian . Weibull . Return period . Sefidrud
* Esmaeel Dodangeh [email protected] * Binh Thai Pham [email protected] * Amirhosein Mosavi [email protected] Extended author information available on the last page of the article
Dodangeh E. et al.
1 Introduction Floods are among the most devastating natural disasters that cause mortalities and financial losses in the affected areas. They are important not only for their destructive effects at the time of occurrence but also for their post-disaster damaging effects persisting for a long time. Global Assessment Report on Disaster Risk Reduction (UNISDR 2015) indicates that flood mortality rate is increasing in developing countries such as Iran. The flood mortality rate has increased by 11% in the Middle East and North Africa compared to the last century (Ghomian and Yousefian 2017). Over the past few years, floods have been the most serious natural disaster in Iran. The recent flood of March 2019 affected many parts of the country with a loss of 76 people and damages of 476 million US dollars. Knowledge of flood magnitudes and frequencies is critical for flood preparedness by adopting preventive measures to mitigate their destructive effects. Flood frequency analysis (FFA) is employed for estimating flood magnitudes for given return periods; economically safe designs of hydraulic structures such as dams, culverts,
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