Development of Updated Intensity-Duration-Frequency (IDF) Curves Using Bias-Corrected IMERG Satellite Data for Urban Flood Management at the Bohicon Synoptic Station, Benin

In the context of climate change and rapid urbanization, Beninese cities like Bohicon are increasingly exposed to frequent flooding. Estimating design flows for hydraulic drainage systems relies, among other tools, on intensity-duration-frequency (IDF) curves. This study aims to construct IDF curves for the Bohicon synoptic station using bias-corrected IMERG satellite rainfall data calibrated with local ground measurements. Maximum rainfall intensities extracted from a 23-year dataset (2000-2023) were fitted to several extreme value probability distributions, including the Gumbel and Weibull distributions, with coefficients of determination (R²) reaching 0.98 for the best fits. Three empirical models—Montana, Keifer-Chu, and Talbot—were tested for constructing the IDF curves. The results show that the Talbot model offers the best statistical performance for all return periods (2 - 100 years), with an RMSE of less than 5 mm/h for T = 2 years and less than 25 mm/h for T = 100 years, reflecting low error and satisfactory reliability of the adjustments, especially for short to medium return periods. For example, for a one-hour rainfall duration and a 10-year return period, the estimated intensity reaches 84 mm/h, compared to 62 mm/h with historical curves. These new IDF curves, calibrated locally and incorporating recent precipitation variability, provide more accurate estimates of extreme rainfall intensities over different durations. They are therefore particularly well-suited to the hydraulic design of urban drainage systems in Bohicon. This research offers a modern and reliable alternative to the historical IDF curves developed by the Inter-African Committee for Hydraulic Studies [1], which were based on limited and outdated rainfall data. The proposed curves provide an updated and robust basis for hydrodynamic flood simulation and resilient urban planning in the face of hydroclimatic extremes.