COASTAL HOME ELEVATION FOR FLOOD MITIGATION: STRUCTURAL SAFETY AND BENEFIT/COST ANALYSIS

Abstract

**Please note that the full text is embargoed until 08/01/2025** construction practice along the Texas Gulf coast under uniform floor live load. The first specimen had four panels with monolithically poured grade beams around each panel, while the second specimen had two panels with monolithically poured grade beams supported by additional steel beams. The second specimen also included carbon fiber reinforced polymer (CFRP) laminate retrofitting under one of the panels. The slabs were supported by concrete block masonry piers with various contact conditions. It was found that the typical contractor-determined elevation layout can withstand the building code-mandated floor live load. Increased column spacing decreased slab load capacity as expected. The CFRP layer did not contribute to the moment capacity as the concrete slab itself was able to carry the applied loads and the CFRP layer was not engaged. The results obtained through running those models through a parametric study were then compiled into a database where each model is categorized into a series of parameters ranging from material properties to support configurations. Finally, an interface was created that allows the user to pick and choose a specific elevated slab and support configuration within the database that would inform the user of the configuration's capacity and whether it meets the minimum design live load established by the International Residential Code. Flood mitigation methods, including the likes of elevation and demolition, are of very high importance for decreasing flood damage and casualties. A benefit-cost analysis (BCA) is generally performed to compare the cost of mitigation projects versus the benefits, which are avoided costs incurred through loss of property or life. The Federal Emergency Management Agency (FEMA) had compiled a BCA calculator that includes several factors to quantify the benefits from undertaking a flood mitigation project. Despite its importance, the underlying methodology employed by the calculator has inherent flaws in both usage and interpretation of results. In this study, a few published concerns about the omission of important parameters in the BCA were examined, specifically the shortcomings and safety concerns for the methods of elevation and demolition. Examples are the unintended wealth inequality of users, missing benefits for specific mitigation methods and the relative merits of home elevation vs. home demolition, among others. For coastal Texas areas, the enhancement of the benefit-cost ratios (BCRs) from considering additional logical factors is examined. The risk premium factor increased the BCR with severity of flood damage and depletion of the user’s yearly income. The social welfare factors also multiplicatively affected the BCR depending on the property location. The BCR increased at locations with less average income-per-capita and vice versa. Two additional factors related to demolition as a mitigation method were examined - recycling of construction demolished material (CDM) and the cost of landfill usage. The BCR could increase by the market cost of the CDM and with increased recycling of the demolished products. The enhanced BCA approach is more realistic and will allow users and funding agencies to logically select flood mitigation projects. This will allow enhanced flood resiliency for coastal communities.