Estimating the flood frequency distribution at seasonal and annual time scales

Abstract

Abstract.We propose an original approach to infer the flood frequency distribution at seasonal and annual time scale. Our purpose is to estimate the peak flow that is expected for an assigned return period T , independently of the season in which it occurs (i.e. annual flood frequency regime), as well as in different selected sub-yearly periods (i.e. seasonal flood frequency regime). While a huge literature exists on annual flood frequency analysis, few studies have focused on the estimation of seasonal flood frequencies despite the relevance of the issue, for instance when scheduling along the months of the year the construction phases of river engineering works directly interacting with the active river bed, like for instance dams. An approximate method for joint frequency analysis is presented here that guarantees consistency between fitted annual and seasonal distributions, i.e. the annual cumulative distribution is the product of the seasonal cumulative distribution functions, under the assumption of independence among floods in different seasons. In our method the parameters of the seasonal frequency distributions are fitted by maximising an objective function that accounts for the likelihoods of both seasonal and annual peaks. In contrast to previous studies, our procedure is conceived to allow the users to introduce subjective weights to the components of the objective function in order to emphasize the fitting of specific seasons or of the annual peak flow distribution. An application to the time series of the Blue Nile daily flows at the Sudan-Ethiopia border is presented.

Unravelling past flash flood activity in a forested mountain catchment of the Spanish Central System

“…In the case of the largest event on record (1936), we also demonstrate that, depending on the seasonality of flash floods, events will not necessarily be triggered by the most important hydrometeorological event and/or the largest precipitation recorded during a year. The time series presented in this study also highlight the importance of independent, seasonal floodfrequency analyses to obtain reliable flood hazard assessments (Baratti et al, 2012;Merz et al, 2014).…”

Characterizing and Modeling Seasonality in Extreme Rainfall

“…Most of the established methods are devised to identify the temporal span of a wet season and assess its significance, typically by a priori identifying a single wet season. For example, directional statistics are typically applied to identify the high flow season (Baratti et al, ; Chen et al, ; Cunderlik et al, ) and have also been applied to characterize the timing of seasonal rainfall (Lee et al, ; Parajka et al, , ). However, directional statistics are inefficient when extremes occur over multiple seasons, which is very likely in the case of rainfall (Cunderlik & Burn, ).…”

Sensitivity of flood frequency analysis to data record, statistical model, and parameter estimation methods: An evaluation over the contiguous United States

“…The choices of statistical distribution and of the parameter estimation method used to model extreme values affect the FFA estimates, and have been thoroughly explored in past studies (Ahilan, Amp, Sullivan, & Bruen, 2012;Baratti et al, 2012;Bobée, Cavadias, Ashkar, Bernier, & Rasmussen, 1993;Haddad & Rahman, 2010;Haktanir & Horlacher, 1993;Kidson & Richards, 2005;Meshgi & Khalili, 2008;Michele & Rosso, 2001;Villarini & Smith, 2010;Wilson et al, 2011). Log Pearson type III (LP3), GEV distribution, Extreme Value type I (EV1), GPD are frequently adopted.…”