The complementary resilience hypothesis: Disaster-type asymmetry in urban complex adaptive systems

School of Architecture and Urban Planning, Nanjing University, Nanjing 210093, China

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Abstract

Climate change is intensifying both natural disasters and systemic crises in cities worldwide. Existing urban resilience theory rarely examines how different disaster types interact asymmetrically with different urban subsystems. Drawing on Complex Adaptive System (CAS) theory, this paper proposes the Complementary Resilience Hypothesis (CRH): when a disaster mainly damages the material subsystem of a city, recovery capacity is likely to come from the resilient immaterial subsystem; when a disaster mainly disrupts the immaterial subsystem, robust material infrastructure becomes the recovery engine. We propose two diagnostics — the Complementary Resilience Score (CRS, harmonic mean of material subsystem resilience M and immaterial subsystem resilience N) and the Complementary Gap Index (CGI) — together with an empirical collapse threshold m*, below which complementary recovery mechanism fails. We operationalise the framework with a 5 + 5 indicator system derived from Xu et al.'s ten urban subsystems. Three cases illustrate the hypothesis: Hurricane Katrina in New Orleans, China's typhoon and flood response, and COVID-19 across major cities. We also present a hazard-profile decision matrix that translates the hypothesis into structural-versus-social investment guidance.