ANALYSE FREQUENTIELLE DES PRECIPITATIONS EXTREMES DANS LA COMMUNE DE BONOU (VALLEE DE LOUEME, BENIN)

Floods are among the most frequent natural disasters in Benin, and the commune of Bonou, located in the alluvial plain of the Oueme River, is one of the most affected areas. Yet no precipitation thresholds calibrated at the communal scale existed to guide operational risk management decisions. This study applies annual maximum (AM) series frequency analysis to daily rainfall data from the Croix-Rouge station in Bonou over the period 1995-2025 (n = 31 years), comparing three statistical distributions, Gumbel, Log-Normal, and GEV using the Kolmogorov-Smirnov (KS) test. The GEV distribution provides the best fit for June, the annual peak month (KS p = 0.902; AM mean = 55.3 mm). Estimated return period thresholds for June are: T2 = 54 mm/d, T5 = 70 mm/d, T10 = 79 mm/d, and T20 = 87 mm/d. Daily exceedance probabilities reach 6.9% for 30 mm and 2.4% for 50 mm in June. The subequatorial regime rainfall generates two annual activation windows (April-July and September-November), with a dry pause in August. These thresholds provide a scientific basis for designing hydrological alerts and parametric cash transfer mechanisms targeting vulnerable households in the commune.