Analysis and risk evolution of floods and cyclones in Sri Lanka from 1975 to 2025 towards resilient strategies

Abstract

Sri Lanka has witnessed a struggle with floods and cyclones, transitioning from occasional emergencies to persistent and growing threats. This study provides the first consolidated long-term temporal analysis that uniquely integrates 50 years (1975–2025) of meteorological trends with a parallel critical evaluation of monitoring technology evolution and institutional governance efficacy. Using Mann-Kendall trend analysis and Pettitt change-point detection, key statistically significant trends were demonstrated: cyclonic disturbance frequency increased from 1.3 to 4.1 systems/year (p<0.001), and extreme rainfall intensity rose by +12.2 mm/decade (p<0.05). Change-point analysis identified 1998 as a statistically significant inflection year (Pettitt test, p<0.05), after which the cyclonic rainfall contribution increased by 18–25% in the northern and eastern provinces. While monitoring capabilities have advanced from rain-gauge dependence (pre-1990) through the satellite era (1990– 2000 s) to real-time Earth observation integration (post-2015), a critical institutional gap remains. This “last-mile” problem is operationally defined as the persistent gap between the forecast lead time and actual evacuation completion times, revealing that a 6-fold increase in forecast lead time (from 12 to 24 h in 1975–1990 to 72– 168 h in 2015–2025) has yielded no proportional improvement in evacuation times, which remain stagnant at 18–36 h. Based on this analytical evidence of persistent institutional failure despite technological progress, this study conceptually proposes an integrated Sri Lanka Multi-Hazard Risk Monitoring and Decision-Support Platform (SL-RISK) that couples technical data integration with community-embedded monitoring, impact-based forecasting, and pre-arranged institutional response mechanisms, outlined with a phased 18–36-month implementation roadmap. Without addressing this governance-technology mismatch, technological advances remain underutilised, perpetuating cycles of preventable disaster losses among vulnerable populations.