Contemporary disasters increasingly manifest as systemic phenomena with cascading effects that transcend traditional boundaries, challenging conventional hazard-focused management approaches. This chapter examines how disasters reveal hidden interdependencies between diverse systems through a comparative analysis of the 2004 Indian Ocean Tsunami and the 2011 Thailand floods. Employing a Development-Environment-Disaster (DED) nexus framework and interdependency typology, this study integrates empirical data, field observations (2005–2023), government assessments, and supply-chain datasets to trace causal pathways connecting pre-disaster vulnerabilities to cascading impacts. The analysis identifies four critical interdependency mechanisms—functional, spatial, institutional, and temporal—linking local vulnerabilities to global processes through economic integration, environmental transformation, and governance fragmentation. The tsunami reveals how tourism development and environmental degradation created transboundary vulnerabilities across 14 countries, resulting in 230,000 fatalities, while the floods demonstrated economic cascade effects through global manufacturing networks, generating $US 46.5 bn in losses. Both cases expose how globalization transforms vulnerability patterns by creating unprecedented risk configurations, spatial exposure concentrations, and temporal risk accumulation through development decisions prioritizing economic returns over resilience. Findings illuminate governance challenges, including sectoral fragmentation, political scale mismatches, and power asymmetries in risk distribution. This research advances disaster studies by providing analytical tools for mapping complex interdependencies and contributes theoretical insights into systemic risk emergence, informing governance innovations for addressing transboundary challenges in an interconnected world.