Long-term dynamics of flood impacts in Sichuan, China (1644–1911) underscore a holistic approach to flood risk management

Risk management has reduced vulnerability to floods in many regions, yet their impacts continue to rise. Understanding the drivers of these changing impacts is urgent for effective action, but empirical evidence remains limited, particularly from long-term historical perspectives. Drawing on extensive Chinese historical documents, this study develops a composite index to quantify the overall societal impacts of floods, as manifested across six interrelated subsystems: environment, production, infrastructure, population, economy, and social order. An annual series of the flood impact index for Sichuan, southwestern China, is reconstructed for the period 1644–1911 (the Qing dynasty). Flood impacts exhibit a fluctuating yet overall increasing trend, with three turning points (1727, 1779, and 1856) defining four phases. These phases are characterized respectively by low flood frequency with limited impacts, increasing mortality, recurrent famine, and widespread disruptions to socioeconomic order. Notably, from the nineteenth century, cascading effects became increasingly pronounced, complicating impact chains and amplifying flood impacts across multiple interconnected subsystems. Drawing on the IPCC risk framework and integrating natural and socio-economic indicators, this study identifies the dominant drivers of the stepwise escalation of flood impacts. The increase in impacts from Phase 1 to Phase 2 was driven by rising exposure associated with rapid population growth and cropland expansion. The shift from Phase 2 to Phase 3 was dominated by increasing vulnerability linked to declining per capita cropland availability and frequent warfare. The transition to Phase 4 resulted from the combined effects of rising hazard, exposure, and vulnerability.

Historical experience suggests the need for a holistic, systems-based approach to flood risk management. The Sichuan case illustrates how reductions in vulnerability can be outweighed by rising exposure, a dynamic that remains evident in contemporary climate adaptation. Rather than prioritizing vulnerability alone, hazard, exposure, and vulnerability need to be considered jointly. Moreover, early identification and intervention targeting impact events with cascading potential are critical for limiting damage in increasingly interconnected systems.