Cotonou, the economic capital of Benin, is suffering from the impacts of climate change, particularly evident through recurrent floods. To effectively manage these floods and address this issue, it is crucial to have a deep understanding of return periods and hydroclimatic parameters (such as intensity-duration-frequency (IDF) curves and related coefficients), which are essential for designing stormwater drainage structures. Determining return periods and these parameters requires statistical analysis of extreme events, and this analysis needs to be regularly updated in response to climate change. The objective of this study was to determine the necessary return periods and hydroclimatic parameters to improve stormwater drainage systems in the city and its surroundings areas. This required annual maximum precipitation series of 1, 2, 3, 6, 12, and 24 h for 20 years length (1999–2018) as well as flood record data. The intensity series, derived by dividing the amount of rainfall by its duration, was adjusted using Gumbel’s law. IDF curves were constructed based on Montana and Talbot models, and their coefficients were determined according to the corresponding return periods. In 2010, which witnessed devastating floods in the country, the return period for the most intense rainfall events was 40 years, followed by 2013 with a return period of 13.4 years. Consequently, the commonly used 10-year return period for the design of stormwater drainage structures in Cotonou is insufficient. The Talbot model produced the lowest mean square errors for each quantile series and coefficients of determination closest to one, indicating that the parameters obtained from this model are well suited for designing hydraulic structures in Cotonou. The hydroclimatic parameters presented in this study will contribute to the improved design of hydraulic structures in the city of Cotonou.

中文翻译：

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气候变化条件下贝宁沿海城市科托努雨水排放重现期和水文气候参数评估

贝宁的经济首都科托努正遭受气候变化的影响，特别是经常发生的洪水。为了有效管理这些洪水并解决这一问题，深入了解重现期和水文气候参数（例如强度-持续-频率（IDF）曲线和相关系数）至关重要，这对于设计雨水排水结构至关重要。确定重现期和这些参数需要对极端事件进行统计分析，并且该分析需要定期更新以应对气候变化。本研究的目的是确定必要的重现期和水文气候参数，以改善城市及其周边地区的雨水排放系统。这需要年最大降水量序列 1、2、3、6、12、20 年（1999-2018）的 24 小时以及洪水记录数据。强度序列是通过降雨量除以持续时间得出的，并使用冈贝尔定律进行调整。IDF曲线是基于Montana和Talbot模型构建的，并根据相应的重现期确定其系数。2010年，该国发生特大洪涝灾害，最强降雨事件的重现期为40年，其次是2013年，降雨重现期为13.4年。因此，科托努雨水排放结构设计常用的10年重现期是不够的。塔尔博特模型为每个分位数序列产生最低均方误差，并且确定系数最接近 1，表明从该模型获得的参数非常适合科托努水工结构的设计。本研究中提出的水文气候参数将有助于改进科托努市水工结构的设计。