Exploring the intensity, duration and frequency of rainfall in selected Southern Nigeria's urban landscapes

Southern Nigeria faces recurring challenges from high annual rainfall, thus resulting to frequent floods, gully erosion, damage to agriculture, water systems, and infrastructure. Studies that employed recent long span rainfall data with the use of precipitation duration curves in these areas are sparse. Forty years (1982 to 2021) maximum daily rainfall data for Akure, Calabar, Enugu, Ikeja, Owerri, and Yenegoa were scaled down to sub-daily intensities. The data were analysed using the Gumbel probability plotting position to develop IDF curves and equations for return periods between 1 to 500 years in conjunction with rainfall durations ranging from 0.25 to 24 hours. Performance evaluation tests assessed the suitability of developed IDF equations. The IDF equations demonstrated high accuracy since a determination coefficient (R2) of 0.97 was obtained. Understanding rainfall characteristics in these locations can inform water policy development and also enhance flood management for the support of water resource planning and governance.