Urban Flooding and Waterborne Illness among Bahini-Bharalu Basin Households, Guwahati, India

Background: Urban flooding is a compound socio-environmental health risk, but its household-level association with waterborne illness in ecologically degraded Indian river basins remains under quantified. This study examined this association in the Bahini-Bharalu River basin, Guwahati. The aim was to estimate the prevalence of flooding and waterborne illness among Bahini-Bharalu basin households and determine their adjusted association. Methodology: A cross-sectional survey of 402 households across nine wards was conducted using two-stage stratified random sampling. Exposure was self-reported flooding (past five years) and outcome was self-reported waterborne illness (past 12 months). Given near-complete separation, Firth bias-reduced logistic and modified Poisson regression were used as the principal analyses. Results: 309 households (76.9%) reported flooding and 287 (71.4%) reported illness; illness prevalence was 89.6% among flooded versus 10.8% among non-flooded households. The adjusted Firth odds ratio was 41.5 (95% CI: 16.4-105.2) and the adjusted prevalence ratio 6.70 (95% CI: 3.60-12.40, p <0.001). Male sex and regular foul odour were each independently associated with higher illness risk, whereas piped-water access was associated with lower risk. Conclusions: Flooding showed a strong, consistent association with waterborne illness, though the cross-sectional design and shared self-report warrant cautious interpretation. Sewage and waste water treatment, solid-waste management, piped water expansion and river restoration are priority interventions.