Beyond Climate Change: Empirical Evidence that Lagdo Dam Operations and not Rainfall Variability Drive Catastrophic Flooding in Nigeria's Niger Delta

Abstract

The Niger Delta experiences recurrent catastrophic flooding often attributed to climate change in policy discourse. However, local communities consistently identify releases from Cameroon's Lagdo Dam as the principal driver, indicating a transboundary governance issue insufficiently addressed in disaster risk reduction frameworks. This study investigates the relationship between Lagdo Dam operations and flood occurrence in Delta State, Nigeria, over a 30-year period (1995–2024), integrating climate trend analysis with community knowledge. A mixed-methods design combined Mann–Kendall trend analysis, Sen’s slope estimation, and Pettitt change-point detection for precipitation and temperature data with community perceptions obtained from 761 household surveys (94.0% response rate), 36 key informant interviews, and 18 focus group discussions across 18 communities. Geospatial analysis applied Principal Component Analysis to construct a Social Vulnerability Index and used Geographically Weighted Regression to model spatial flood impacts. Results show significant warming (+1.17 °C over 30 years, p < 0.01) but no statistically significant trend in annual precipitation (p > 0.05). Change-point analysis identified 2012 as a major break in flood frequency (p < 0.001), without a corresponding precipitation shift. Notably, 86% of respondents attribute flooding primarily to Lagdo Dam releases. The vulnerability index identified three dimensions explaining 73.4% of variance, while spatial clustering along the Niger River corridor was significant (Moran’s I = 0.342, p < 0.001). Five communities representing 38% of the population accounted for 72% of modeled risk. Findings demonstrate that transboundary dam operations, rather than precipitation change, are the dominant driver of flooding, highlighting the need for strengthened Nigeria–Cameroon water governance agreements alongside locally targeted vulnerability reduction strategies.