Flood Frequency Analysis of Niandan River at Baro, Nigeria

Itolima Ologhadien

doi:10.7176/cer/11-4-03

Abstract

The determination of appropriate probability distribution is crucial for flood – risk reduction and mitigation of flood –induced damages in flood plains. This paper investigates the selection of an appropriate probability distribution for at – site flood frequency analysis using annual maximum series of Niandan River at Baro. The model results were subjected to five goodness of fit –tests(i.e. Probability plots, Probability Plot Correlation Coefficient (PPCC), Percent bias (PBIAS), Nash- Sutcliffe efficiency(NSE) and RMSE-observations standard deviation (RSR) and performance scoring/ranking to identified the best – fit distribution.The Normal, and Weibull distributions have been identified as the top two distributions for Niandan at baro. Assessment of other of flood frequency analysis studies across Nigeria show that no single distribution has been found appropriate for whole country. Consequently, research work for the search of best – fit distribution for Nigeria will continue into the future. Keywords : Flood flow, Flood frequency analysis, PPCC, Flood quantiles, efficiency criteria, DOI : 10.7176/CER/11-4-03 Publication date :May 31 st 2019

Highlights

Flood frequency analysis is concerned with the assessment of flood magnitudes of stated frequency for use as input into the process of flood risk assessment and management
The determination of appropriate probability distribution is of fundamental importance for flood-risk reduction and mitigation of flood-induced damages, as a wrong choice could lend to significant error bias in and design flood estimates, at higher return periods, leading to either under-or over-over-estimation, which may have detrimental impacts on engineering practice and economy (Rahman et al, 2013)
The probability plot is a plot of the sample quantiles Yi against theoretical quantiles of Qi, where Φ-1 is the inverse of the cumulative standard normal distribution, and Pi denote the appropriate quantiles probabilities

Summary

Introduction

Flood frequency analysis is concerned with the assessment of flood magnitudes of stated frequency (or degree of rarity) for use as input into the process of flood risk assessment and management. Assessment of hydrologic risk requires the estimation of the probability of occurrence of the flood magnitude that would inundate or damage the planned infrastructure. It is these probabilities that are estimated through flood frequency analysis. The determination of appropriate probability distribution is of fundamental importance for flood-risk reduction and mitigation of flood-induced damages, as a wrong choice could lend to significant error bias in and design flood estimates, at higher return periods, leading to either under-or over-over-estimation, which may have detrimental impacts on engineering practice and economy (Rahman et al, 2013). Hydrologic data for flood frequency analysis are based on a set of fundamental assumptions, namely; the series (i) consistent,(ii) is trend-free and (iii) constitute a stochastic the processes whose random component follows the appropriate probability distribution function (Adeloye and Montaseri, 2002). The double mass curve is the most widely used technique for evaluating a time series for consistency

Methods

Results

Conclusion