Determination of Hydrological Flood Hazard Thresholds and Flood Frequency Analysis: Case Study of Nokoue Lake Watershed
Year: 2025
Type: article
Abstract: A flood is defined as a relatively high flow rate or water level in a river or body of water, characterized by an elevation above the norm, leading to the inundation of low-lying areas or bodies of water that are not normally submerged. Almost every year, floods of significant magnitude impact the Nokoue lake basin, endangering nearby populations as they greatly affect the economy and infrastructure development. The unresolved issue of flooding in Nokoue lake necessitates a thorough study and analysis of specific flow models, particularly those concerning the frequency, probability, and scale of flooding. In this context, the present article on threshold determination and flood frequency analysis is highly valuable in mitigating the chronic flooding problem of Nokoue lake. Flood frequency analysis involves interpreting the historical flood data and predicting future probabilities. Annual data on the maximum water level of Nokoue lake over 27 years, from 1997 to 2022, was used for this purpose. The peak water level indices of Nokoue lake and classification were used to characterize flood thresholds. The Gumbel extreme value distribution method, the generalized extreme value distribution method, and the generalized Pareto method were used to test the probability of flood occurrence. The analysis results indicate that flood hazard thresholds are defined as follows: from negative infinity up to below 3.94 m for limited risk, from 3.94 m up to 4.04 m for moderate risk, from above 4.04 m to 4.14 m for significant risk, and from above 4.14 m to 4.95 m for critical risk. Among the flood frequency analysis methods, the Gumbel extreme value distribution is considered more effective and suitable for estimating flood occurrence probabilities and for designing flood control measures for Nokoue lake with a root mean square error (RMSE) of 0.0724, compared to 0.0754 and 0.0761 for the GEV and GPA distributions, respectively. The position and scale parameters (φ; α) of the Gumbel distribution were estimated to be 3.802 and 0.249, respectively. This allows for the calculation of the probability of an extreme water level occurring within a return period in a single day. Thus, the extreme water levels (flood quantiles) associated with return periods of 10, 50, and 100 years, as determined by the Gumbel distribution, are 4.36m, 4.77m, and 4.95m, respectively. Exceptional and very exceptional hydrological events have return periods of 100 and 150 years, corresponding to peak flow levels ranging from 4,95m and 5,05m respectively. These values are of crucial importance for the design of flood prevention structures (infrastructure) intended to mitigate flood risk.
Source: Water
DOI: 10.3390/w17081147
Authors: Namwinwelbere DABIRE, E. C. EZIN, A. M. Firmin
Institution: Université d'Abomey-Calavi
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,137
OpenAlex ID: W4409407892