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TABLE 9-1 ESTIMATED COST TO ELEVATE A NEW STRUCTURE ON FILL OR COLUMNS Item Estimated Cost Estimated Cost to Elevate 3 Feet' to Elevate 5 Feet' I ncreased Cost to Elevate $1760. $2400. Total First Cost $1760. $2400. Annual Cost' $ 142. $ 193. Annual Cost as Percentage of 0.5 .6 Structure Value 1 Based on an estimate of $1.10 per square foot for a 1600 square foot, $30,000 structure. 2 Amortized at 7 percent over 30 years. 3 Based on an estimate of $1.50 per square foot for a 1600 square foot, $30,000 structure. Economic Feasibility When a new structure is elevated to some higher elevation, damage is reduced by eliminating damage which otherwise would occur below the elevated elevation. At a lower el~vation damage would occur when inundated by less frequent floods, while at a higher elevation these floods would not cause damage if they are below the raised height. Damage reduced is the difference in damage with and without the structure elevated. Th~ without condition depends upon local regulation of flood plain land. In the absence of any regulations a property owner may choose to locate a structure at any flood plain elevation desired. Under the National Flood Insurance Program new structures are required to locate at or above the 100 year flood elevation. The without condition elevation then is based upon one of these two conditions, or some other conditions, if for example a variance were granted. The with condition elevation is the elevation to which the new structure is being raised. Economic feasibility is determined by comparing damage r~duced by raising a structure a certain number of feet to the cost to do the raising. Figures 9-2 through 9-9 show expected annual damage reduced for new type structures raised three feet and five feet respectively. Damage reduced is to structure and contents. These data were computed by first computing expected annual damage at a base elevation (100.0 feet), then computing damage with each structure raised three feet and five feet (103.0 and 105.0 feet respectively). Results of this analysis show damage reduced varies by type structure, flood hazard factor, and location in the flood plain. The annual cost for raising a structure three feet, expressed as a percentage of structure value (0.5 percent in Tabl~ 9-1) is plotted on Figures 9-2 through 9-5. A comparison with damage reduced for each type structure shows that the cost is exceeded for all locations in the flood plain, all flood hazard factors and all type structures. 65