Risk-based adaptation framework for levees under evolving climatic and non-climatic stressors

Levees have evolved from agricultural flood defenses into critical infrastructure systems whose failure poses cascading risks to communities, economies, and ecosystems. Under intensifying climatic and non-climatic stressors, many levees are now required to perform beyond their original design conditions. Despite this, adaptation remains largely reactive, often triggered by catastrophic failures rather than guided by systematic, forward-looking risk prioritization. Here, we propose a risk-informed, multi-criteria framework for levee adaptation that integrates physical, socio-economic, and governance dimensions of risk. The overarching objective is to quantify levee risk under current and projected future scenarios and to support the co-development of adaptation strategies that minimize this risk over time while balancing technical reliability, economic feasibility, and social equity. The framework is structured around five interconnected steps. Step 1 introduces the Levee Risk Index (LRI), a dynamic composite screening tool that integrates indicators across exposure, hazard, and vulnerability domains to prioritize leveed communities under current and projected future conditions. Step 2 embeds structured stakeholder engagement throughout the framework, ensuring that community knowledge, constraints, and equity objectives inform technical decision-making. Step 3 involves a two-tiered risk assessment structure spanning regional and structural scales, integrating hydrodynamic modeling, breach probability estimation, and consequence analysis. Step 4 synthesizes stakeholder inputs and quantitative risk outputs into adaptation pathways evaluated through multi-objective analysis and optimization, enabling decision-makers to navigate tradeoffs between objectives. Step 5 establishes continuous monitoring of hazard, vulnerability, and exposure conditions. The framework is iterative, scalable, and transferable, providing a systematic basis for proactive and adaptive levee risk management.