Economically optimizing elevation of new, single-family residences for
flood mitigation via life-cycle benefit-cost analysis
Abstract
Construction with freeboard – vertical height of a structure above the
minimum required – is commonly accepted as a sound investment for flood
hazard mitigation. However, determining the optimal height of freeboard
poses a major decision problem. This research introduces a life-cycle
benefit-cost analysis (LCBCA) approach for optimizing freeboard height
for a new, single-family residence, while incorporating uncertainty,
and, in the case of insured homes, considering the costs from losses,
insurance, and freeboard (if any) to the homeowner and National Flood
Insurance Program (NFIP) separately. Using a hypothetical, case study
home in Metairie, Louisiana, results show that adding 2 ft. of freeboard
at the time of construction might be considered the optimal option given
that it yields the highest net benefit, but the highest net benefit-cost
ratio occurs for the 1 ft. freeboard. Even if flood loss reduction is
not considered when adding freeboard, the savings in annual insurance
premiums alone are sufficient to recover the construction costs paid by
the homeowner if at least one foot of freeboard is included at
construction. Collectively, these results based on conservative
assumptions suggest that at the time of construction, even a small
amount of freeboard provides a huge savings for the homeowner and
(especially) for the financially-strapped NFIP. For community planners,
the results suggest that wise planning with reasonable expectations on
the front end makes for a more sustainable community.