Cost-effectiveness of federal CDBG-DR Road Home Program mitigation assistance in Jefferson Parish, Louisiana

摘要

Abstract After Hurricanes Katrina and Rita in 2005, the State of Louisiana received federal Community Development Block Grant Disaster Recovery (CDBG-DR) assistance, administered by the Louisiana Office of Community Development (OCD) as the Road Home Program, to provide homeowners with the required matching funds for elevating damaged homes under the Federal Emergency Management Agency (FEMA) Hazard Mitigation Grant Program (HMGP). This research evaluates the cost-effectiveness of the Road Home Program elevation mitigation assistance for a case study of homes in Jefferson Parish, Louisiana, using benefit–cost analysis (BCA) based on average annual loss (AAL) prediction. We use multiple return period flood depths from FEMA RiskMAP non-regulatory flood depth and calculate flood risk reduction as the difference between pre- and post-elevation AAL. We compute benefit–cost ratio (BCR) and net benefit–cost ratio (NBCR) of the elevation mitigation investment across multiple time horizons, considering several funding scenarios. Then, we determine optimal first-floor height (FFH) by foundation type and 100-year flood depth. The analysis reveals that elevating existing homes by either 3 feet above the ground or to the base flood elevation (BFE; 100-year flood elevation), whichever is higher, reduces the median AAL by 98%. This elevation generates a BCR of 1.5 and 1.7 over a 30-year mortgage and a 70-year building lifetime, respectively, if the benefit is allocated proportionately. These results enhance understanding of cost-effectiveness of federal elevation mitigation investments, benefits of elevating homes above the minimum requirements, and most effective elevated heights for homes.