A two-stage robust decision-making framework (2S-RDM) for flood risk adaptation under deep uncertainty.

Area of Science:

• Environmental Science
• Climate Change Adaptation
• Risk Management

Background:

• Flooding poses significant challenges to societies, exacerbated by deep uncertainty in climate change projections.
• Effective adaptation strategies are crucial for managing future flood risks, particularly in vulnerable regions like the Yangtze River Basin.

Purpose of the Study:

• To propose and evaluate a Two-stage Robust Decision Making (2S-RDM) framework for developing flexible and robust flood risk management strategies.
• To identify effective adaptation measures and their combinations under deep uncertainty for the Yangtze River Basin until 2050.

Main Methods:

• Simulated flood risks across approximately 0.6 million scenarios until 2050, considering uncertainties in climate, socio-economic factors, industrial structure, and population aging.
• Examined the effectiveness of four adaptation measures: building elevation, tunnel construction, population relocation, and river basin conservation, including their combinations.
• Utilized the 2S-RDM framework to identify robust strategies meeting specific population impact and economic loss thresholds.

Main Results:

• Without adaptation, 0.9 to 27.3 million people and $33.8 to $198.5 billion in economic losses are projected in the Yangtze River Basin by 2050.
• Identified 24 global robust strategies that limit affected population to <0.05% and economic losses to <0.02% in over 80% of simulated scenarios.
• Hybrid strategies integrating engineering (e.g., Elevation++, Tunnel++) with soft adaptation (e.g., Relocation) were found to be the most effective.

Conclusions:

• The 2S-RDM framework provides a valuable tool for designing flood adaptation strategies that are robust across diverse scenarios and flexible for decision-makers.
• Hybrid adaptation strategies offer a promising approach to effectively manage flood risks under deep uncertainty.
• The study offers actionable insights for enhancing flood resilience in the Yangtze River Basin and other vulnerable regions.