How Hurricane Katrina influenced the design of hurricane protection and risk reduction systems and national approaches to risk and resilience. Part 2: Designing the Hurricane and Storm Damage Risk Reduction System and resulting long-term engineering guidance and practice changes

Following Hurricane Katrina, the US Army Corps of Engineers, supported in part by the risk and reliability analysis conducted by the Interagency Performance Evaluation Task Force (IPET), made a major shift from ‘protection’ to ‘risk reduction’ as the principal goal in flood mitigation. The mitigation of the flood risk in Southeast Louisiana was embodied in the design and construction of the ‘Hurricane and Storm Damage Risk Reduction System’, the post-Katrina initiative for New Orleans flood mitigation. It also spawned a major overhaul of many of the Corps of Engineers’ technical guidance and engineering practice documents, incorporating risk as a key measure in the planning and design processes. The criteria applied for the design of the HSDRRS are discussed, with summaries of the associated major changes in Corps engineering guidance and practice relevant to flood mitigation. HIGHLIGHTS The losses from Hurricane Katrina and subsequent forensic and risk analyses for New Orleans resulted in substantial changes to the knowledge base and guidance for planning and designing coastal risk reduction systems.; The new knowledge was a substantial input to the design of the Hurricane and Storm Damage Risk Reduction System that is currently in place in New Orleans.; The processes used were considerably different from past practice and resulted in a more robust and resilient system with some capacity to deal with uncertainty and change. This paper highlights the new processes.; The same knowledge base was the stimulus for significant changes to the US Army Corps of Engineers engineering guidance and practice documents. A major change was the incorporation of risk-based decision making in many aspects of project development and execution.