The International Guidelines on Natural and Nature-Based Features for Flood Risk Management, published by the U.S. Army Corps of Engineers, NOAA, the Environment Agency of the United Kingdom, Rijkawaterstaat, and the World Bank in September 2021, was celebrated with a virtual launch party underlining the exciting opportunity for progress. At just over 1,000 pages, the report is a comprehensive guide on planning, design, and engineering process of high impact, large-scale natural and nature-based features (NNBFs). NNBFs are landscape features that provide flood risk management benefits, such as dunes, beaches, wetlands, or reefs.
The Guidelines include case studies from around the world to demonstrate the adaptability of NNBFs to different types of politics, communities, ecologies, and purposes. These examples outline the myriad benefits associated with incorporating nature and natural processes into the engineering process. Benefits include long-term resiliency, expansion of wildlife habitats, climate change mitigation, and increased tourism.
Despite these documented benefits, NNBFs are used less frequently than traditional flood mitigation structures. Across all project stages, NNBFs require a much broader spatial and temporal scope than what most engineers and project managers are accustomed to in order to fully account for their benefits, costs, and performance.
Although the Guidelines mostly consist of technical considerations and case studies to help engineers and project managers, the authors acknowledge that increasing technical knowledge about NNBFs is only the first step toward implementation. Governance and policy play a key role in expanding the implementation of NNBFs. The Guidelines offer a number of governance opportunities to facilitate the construction of these cutting-edge projects.
Stakeholder Engagement. The Guidelines include an entire chapter on stakeholder engagement that emphasizes the need for a structured engagement process. The report argues that stakeholder engagement should include a clear plan to “explore and assess options, agree on assumptions, reduce uncertainty, and plan contingencies.” To facilitate an effective engagement process, government officials should establish a structured process for public feedback addressing economic, environmental, and social aspects of both traditional and nature-based flood risk mitigation projects. Due to their dynamic nature, NNBFs offer opportunities for community involvement in project planning, siting, and even construction.
Flexible Permitting. NNBF structures are more dynamic than traditional structures, which contributes to NNBF projects’ high resiliency. Yet, permitting processes often have strict regulations unable to accommodate differences between NNBF and traditional structures. For example, the United States has strict regulations on modifications to the intertidal environment, so it is generally harder and costlier to obtain permits for wetland NNBFs than flood mitigation structures, like seawalls or levees, which usually sit above the high-tide line. Adding flexibility to the permitting process for natural or nature-based projects would reduce barriers for NNBFs.
Expanding Cost-Benefit Analysis. Economic efficiency is central to decisions about risk reduction projects. The wide range of benefits provided by NNBF projects are more difficult to quantify in a traditional cost-benefit analysis. Policymakers should push for the inclusion of environmental and social factors alongside economic costs and benefits. By requiring projects to review social and environmental factors, policymakers can better capture the short- and long-term costs and benefits of implementation and level the playing field for NNBFs.
Requiring Resiliency. The Guidelines outline four types of resilience as critical to the success of NNBFs: flood risk management, ecological, community, and institutional. While governments across the globe are beginning to include resiliency in their plans and projects, the next step is including clear definitions, methods of incorporation, and performance metrics for all four types of resilience into flood risk management projects. Compared to traditional flood mitigation structures, NNBF projects are more dynamic and have greater capacity for natural recovery, especially when multiple types of resiliencies are considered. Legal or regulatory requirements for developers to include multiple types of resiliencies in their cost-benefit analysis can give NNBF projects the edge in the decisionmaking process.
Performance Metrics. NNBF projects require different kinds of performance metrics than traditional flood mitigation structures. As NNBFs are often most effective at a regional or watershed level, performance metrics should include an understanding of the broader system. Similar to resilience, the Guidelines propose that creating specific metrics for different kinds of performance is key to capturing NNBF benefits. To facilitate NNBF construction, policymakers and regulators should incorporate system-level performance metrics for flood risk management, ecological impact, social impact, and economic performance. The Guidelines suggest that at the programmatic level, having a “broader strategy that assesses multiple projects across the region using a common set of metrics and criteria may be needed.”
Beyond the Guidelines, other organizations are opening up conversations about these issues. The Society for Cost-Benefit Analysis will host a conference in March 2022 about analyzing distributional consequences and equity in cost-benefit analysis. The Nature Conservancy penned an article emphasizing opportunities for NNBF investment in the United States’ recently passed infrastructure bill. Nature-based solutions, especially for coastal management, were elevated as climate-change mitigation measures at COP26.
Ultimately, the Guidelines show a concerted effort by major organizations to push stakeholders to consider creative methods to incorporate resiliency, social impacts, and existing natural features in their plans and designs. Implementing these ideas quickly and effectively will require government programs and officials to remove legal and regulatory barriers for NNBF implementation.