Temporal evolution of extreme rainfall in Maiduguri (1980–2001 vs. 2002–2023): A GEV–GPD return level and climate shift analysis

Abstract

Understanding temporal shifts in extreme rainfall is critical for flood risk management in semi-arid regions. This study examined the changes in Maiduguri, Nigeria's annual and seasonal maximum monthly rainfall during the years 1980–2001 and 2002–2023. The Generalized Extreme Value (GEV) and Generalized Pareto Distribution (GPD) models were used to apply extreme value theory, and Mann-Kendall tests and structural breakpoint analysis were used to identify monotonic trends and climate-driven shifts. The mean annual maxima increased significantly from 206.8 mm in 1980–2001 to 302.9 mm in 2002–2023, with maximum values increasing from 342.7 mm to 521.2 mm, according to descriptive statistics. The 10-year return level increased from 286.4 mm to 419.0 mm (GEV) and from 340.9 mm to 518.4 mm (GPD) between the two periods, confirming intensification according to both GEV and GPD return-level estimates. The Mann-Kendall test verified an upward trend in rainfall maxima, and breakpoint analysis found a statistically significant shift around 2001 (p < 0.05), consistent with Sahel recovery trends. These findings show that Maiduguri's extreme rainfall events have significantly increased since the early 2000s, which has significant ramifications for planning water resources, infrastructure, and flood preparedness. The application of this study lies in supporting data-driven flood risk assessments, updating design standards for urban drainage systems, and guiding climate-resilient infrastructure development in Maiduguri and similar semi-arid regions.