- What mixture of hurricane risk reduction and coastal restoration projects can achieve Louisiana's goals of reducing hurricane risk and stabilizing and rebuilding coastal land, for different budget constraints?
- How can an interactive planning tool help decisionmakers develop a comprehensive master plan that meets diverse objectives under significant financial and other constraints?
Coastal Louisiana's built and natural environment faces risks from catastrophic tropical storms. Concurrently, the region is experiencing a dramatic conversion of coastal land and associated habitats to open water and a loss of important services provided by such ecosystems. Louisiana's Coastal Protection and Restoration Authority (CPRA) engaged in a detailed modeling, simulation, and analysis exercise, the results of which informed Louisiana's Comprehensive Master Plan for a Sustainable Coast. The Master Plan defines a set of coastal risk-reduction and restoration projects to be implemented in the coming decades to reduce hurricane flood risk to coastal communities and restore the Louisiana coast. Risk-reduction and restoration projects were selected to provide the greatest level of risk-reduction and land-building benefits under a given budget constraint while being consistent with other objectives and principles of the Master Plan. A RAND project team, with the guidance of CPRA and other members of the Master Plan Delivery Team, developed a computer-based decision-support tool, called the CPRA Planning Tool. The Planning Tool provided technical analysis that supported the development of the Master Plan through CPRA and community-based deliberations. This document seeks to provide an accessible technical description of the Planning Tool and associated analyses used to develop the Master Plan.
A planning tool helped develop a range of different alternative comprehensive solutions to Louisiana's coast problems to support deliberation among stakeholders and decisionmakers.
- Predictive models estimated the effects of a large set of possible risk-reduction projects and restoration projects for two environmental scenarios (one of moderate conditions and another of less optimistic conditions).
- The Planning Tool evaluated the costs and effects of these projects.
- The tool used an objective function that selected groups of projects (or alternatives) that maximizes flood risk reduction (in terms of expected annual damage) and land building (in terms of area of land) for several funding scenarios between $20 and $100 billion over a 50-year period.
- The tool also calculated the following metrics for risk-reduction projects: residual damage at 50-, 100-, and 500-year flood intervals.
- The tool also calculated the following ecosystem-service metrics for restoration projects: alligator, oysters, shrimp, saltwater fisheries, waterfowl, carbon sequestration, freshwater availability, nutrient uptake, and storm surge and wave attenuation.
- The tool also considered other decision criteria including: distribution of risk across socioeconomic groups, use of natural processes, sustainability, operations and maintenance costs, support of cultural heritage, flood protection of historic properties, support of navigation, flood protection of strategic assets, support of oil and gas, and restoration of critical landforms.
- The tool applied four types of constraints when developing alternatives: financial and natural resource constraints, mutually exclusive project constraints, project inclusion and exclusion constraints, and outcome constraints.
- A process of deliberation with analysis framed and illustrated key policy trade-offs between alternatives in the two scenario types in a future without action and a future with the identified alternative implemented.
Louisiana can significantly reduce hurricane flood risk and stabilize the coastal landscape under favorable future assumptions with the implementation of a 50-year, $50 billion comprehensive master plan.
- The master plan resulting from this analysis, if implemented, would significantly reduce flood risk under either of the two environmental scenarios.
- The master plan, if implemented, would stop the loss of coastal land by 2040 and lead to land growth after that under moderate assumptions. Under less optimistic assumptions, land loss would continue but at a significantly slower rate.
- Louisiana should begin to develop an implementation plan for the 50-year, $50 billion Comprehensive Master Plan for a Sustainable Coast.
- The assumptions were reasonable for the planning phase but will need more-careful examination as the Master Plan is implemented.
- In some cases, the combined effect of projects may have consequences not captured by the Planning Tool, so modifications over time to the plan may be necessary.
- Additional work needs to be done to better quantify the ecosystem and economic benefits of implementing the Master Plan to justify public expenditures.
- More-significant analysis of its performance under different scenarios and potential adjustments will be helpful to ensure that the sequence of projects ultimately implemented is indeed robust to a wide range of futures.
Table of Contents
Model Description and Assumptions
Analyses to Develop the Master Plan
This research was sponsored by the Coastal Protection and Restoration Authority of the State of Louisiana and was conducted in the RAND Gulf States Policy Institute and the Environment, Energy, and Economic Development Program within RAND Infrastructure, Safety, and Environment.
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