- What are the baseline levels of flood risk in different areas of Lafourche, Terrebonne, and Plaquemines parishes in Louisiana?
- How do the benefits of reduced flood risk compare to the costs of elevating structures in Lafourche, Terrebonne, and Plaquemines parishes in Louisiana?
- How many structures could be elevated in Lafourche, Terrebonne, and Plaquemines parishes if different amounts of money were spent in the area?
Through the Natural Disaster Resilience Competition, the U.S. Department of Housing and Urban Development is making nearly $1 billion available to states that have recently experienced a presidentially declared major disaster. The State of Louisiana submitted an application to the Natural Disaster Resilience Competition that proposes using provided funds to elevate residential structures in Plaquemines, Lafourche, and Terrebonne parishes to reduce the risk of future flooding from storm surge. They asked RAND to help develop this proposal by performing a quantitative analysis of the baseline flood risks and different allocations of funds for mitigation across the three parishes. The results show that nonstructural work in Terrebonne and Plaquemines parishes offers the most risk mitigation, and that the State's recommended allocations provide higher benefits than costs for all three parishes.
Exploring Allocations and Outcomes
- This study proposed and analyzed different allocations of funding to communities.
- For each of several project variants, the analysis defined where mitigation should occur, how many structures to elevate, and the estimated cost.
- Different project variants were defined in terms of the size/budget level of the project, the elevation standard applied when elevating residential structures, the project eligibility for areas where flood depths are expected to increase above the level where elevation is a cost-effective option, and how project work in different areas was prioritized.
- RAND developed a decision support tool that allows users to see the areas where structures are elevated once a project definition has been specified, explore projected project costs and counts of the structures mitigated in different geographic areas, compare the benefits and costs of different project variants, and compare alternative projects.
Overall Proposal Outcomes Appear Positive
- In many areas where the State proposes elevating structures, more than 50 percent of the population has low to moderate income, particularly in Terrebonne and Plaquemines parishes.
- The State's recommended project provides higher benefits than costs in each of the three parishes. The benefits and costs are lowest in Lafourche Parish because relatively few structures are elevated. Recommended nonstructural mitigation is more extensive in Terrebonne and Plaquemines parishes.
- The recommended project provides significantly higher benefits than costs at the parish level — net value results are $106 million, $2.5 million and $23 million for Terrebonne, Lafourche, and Plaquemines parishes, respectively, with correspondingly good benefit-cost ratios.
The research reported here was prepared for the State of Louisiana Office of Community Development with the Louisiana Coastal Protection Authority and Water Institute of the Gulf and conducted by the Infrastructure Resilience and Environmental Policy Program, a part of RAND Justice, Infrastructure, and Environment.
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