Development of rainfall intensity – duration – frequency models for Benin city in south-south Nigeria

A major challenge in water resources engineering is the lack of adequate meteorological data for designing and managing infrastructure against extreme rainfall events. This study analyzed 30 years (1993–2022) of daily rainfall data from Benin City, Nigeria, using the annual maximum series method. Rainfall intensities were calculated for durations ranging from 10 to 360 minutes and return periods of 2 to 100 years using Gumbel and Log Pearson Type III distributions. These models address both short-duration storm events and long-term recurrence probabilities, which are essential for flood risk management. Rainfall Intensity-Duration-Frequency (IDF) models were developed using non-linear regression in Microsoft Excel, Model performance was evaluated using statistical metrics like Chi-square, Correlation coefficient (R), Coefficient of determination (R²), and Root Mean Square Error (RMSE). Both models showed excellent fits with low RMSE (0.26- 9.89) , R and R² values ranged between 0.98 -1.00 and 0.99-1.00 respectively . These IDF models are valuable tools for engineers and hydrologists in flood risk mitigation, drainage design, and water resource planning in Benin City, Nigeria.