Economically Optimizing Elevation of New, Single-family Residences for Flood Mitigation via Life-cycle Benefit-cost Analysis

Carol Friedland, Kleinpeter, Shelly

Adding freeboard (additional elevation of the first floor above the 100-year, or base flood, elevation) to a home at the time of construction is accepted as a sound investment for flood hazard mitigation. However, determining the optimal height of freeboard can be difficult due to the lack of robust benefit-cost analysis of adding freeboard at the individual building level (“micro-scale”) – most analyses are done at the community, neighborhood, or city level. As a result, investment in flood mitigation is often overlooked and underused. Therefore, the goal of this study is to evaluate the cost effectiveness of freeboard across a building’s entire expected lifespan.

Using a hypothetical case study home in Metairie, Louisiana, this research used a lifecycle benefit-cost analysis (LCBCA) approach to optimize freeboard height for a new, single-family residence while incorporating uncertainty, costs from losses, and insurance policies among other factors. This study found that adding 2 feet of freeboard at the time of construction may be the optimal option given that it yields the highest net benefit; however, the highest net benefit ratio occurs with 1 foot of freeboard. These findings mean that 1 foot of freeboard provides the largest benefit for the cost but that 2 feet of freeboard provides the most overall cost-effective protection in the study area.

Even if flood loss reduction is not considered when adding freeboard, the savings in annual insurance premiums alone are sufficient to cover the amortized construction costs paid by the homeowner if at least one foot of freeboard is included in construction. Collectively, these results suggest that at the time of construction, even a small amount of freeboard provides huge savings for the homeowner and the National Flood Insurance Program. For community planners, these results suggest that wise planning with reasonable expectations on the front end makes for more sustainable communities.

To see the results in detail and read more about our peer-reviewed publication on this research click on the link below. Gnan, E., Friedland, C. J., Mostafiz, R. B., Rahim, M. A., Gentimis, T., Taghinezhad, A., & Rohli, R. V. (2022). Economically optimizing elevation of new, single-family residences for flood mitigation via life-cycle benefit-cost analysis. Frontiers in Environmental Science, 10.

4/20/2023 2:14:04 PM
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