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Abstract
Societies that rely on conventional flood management infrastructure -- such as levees and dams -- are facing significant challenges in adapting to non-stationary flood regimes driven by climate change and evolving land use. Approaches to hybridize infrastructure with natural features and processes can improve resilience and are becoming increasingly popular solutions to these infrastructure challenges. Such approaches are often called nature-based solutions (NBS) and are supported by a growing literature but are not yet mainstream in professional practice due to critical knowledge gaps associated with the risk mitigation services that may be derived from natural features and processes, as well as their economic defensibility as infrastructure investments. This work addresses these knowledge gaps for levee setbacks (a form of floodplain reconnection) and demonstrates how setbacks are an effective and scalable NBS for large river systems. Knowledge gaps concerning the risk mitigation services of restoring floodplain connectivity in leveed river corridors are addressed qualitatively through the exploration of their underlying mechanisms and are also addressed quantitatively with numerical flood and economic modeling. Uncertainties concerning the economic viability of setbacks are explored quantitatively and with the regulated investment decision-making frameworks of governmental agencies in the US. Setbacks are found to be economically defensible in a variety of contexts, such as in disaster recovery operations and in civil works planning to pre-emptively address levee system vulnerabilities. These contributions to the literature foster greater understanding of how today’s infrastructure challenges may be addressed and include design and economic assessment tools that are actionable in professional practice now.