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<br />Regarding damage, the relationship is much more simple. For structures with basements <br />damage exists below the first floor while for structures without basements it does not (except for <br />minor damage to elevation -1.0 feet). Above the first floor damage potentiai in a structure with <br />basement is slightly less than for a structure without basement. <br /> <br />Combining these three facts the following conclusions may be drawn regarding the decrease <br />(Figure A-7) in expected annual damage between FHF ~ 4.0 and 8.0 for the 10 year and 25 year <br />events at the first floor and the increase for events 2 year and 5 year. The decrease occurs <br />because expected annual damage beiow the first floor is considerably greater for the lower FHF <br />than for the larger FHF and this offsets and exceeds the lesser expected annual damage above <br />the first floor for the lower FHF. Figure A-14 illustrates this point. When the 2 year event is at the <br />first floor, damage in the basement is much smaller and there is not enough difference to offset <br />the much greater damage for the larger FHF occurring above the first floor. Single story <br />structures with no basement have no appreciable damage below the first floor, thus the. general <br />trend of increasing damage with increasing FHF holds. Figure A-15 illustrates this point. <br /> <br />Sensitivity to Skew <br />Figures A-16 through A-19 show the sensitivity of expected annual damage to variations in the <br />elevation-frequency curve. Skew D represents the maximum positive skew variation and skew I <br />the maximum negative skew variation. Results of the analysis show that, <br /> <br />. For structures without basements (1SNB, 2SNB) there is only a small difference between <br />expected annual damage for skew D and skew I when the event at the first floor is the 15 <br />year or greater and the FHF is greater than 4.0. <br /> <br />.. For structures with basements (1SWB, 2SWfl) there is a significant variation (:t 100%) <br />between expected annual damage computed -using skew 0 and skew I when the <br />frequency relationship has a FHF less than about 10.0 <br /> <br />Two measures of variation were investigated - the relative difference in expected annual <br />damage, and percentage difference. The former are reported here because the relative <br />magnitude relates more meaningfully to cost. The percentage difference was highly variable <br />becoming as much as 125 percent. <br /> <br />This means that for structures without basements variations in the skew of the frequency <br />relationship are not likely to be significant except for structures low in the flood plain and.with <br />FHf less than about 4;0. Structures With basements are most sensitive to skew except in the <br />higher range of flood hazard factors. <br /> <br />Sensitivity to Structure Type <br />Structures with basements and structures with a second story, distribute damageable <br />property. over a greater height than do structures with only one story. One would expect <br />differences in expected annual damage depending upon structure type. figures A-9 thru A.11 <br />show some of these differences. As to be expected, damage is greater in a structure with <br />basement than without because the property in the basementis damaged byevents that do not <br />cause damage to a structure without a basement and because events which do cause damage to <br />both type structures (events above the first floor) cause greater damage because of property in <br />the basement. The opposite is true for two story structures. less damageable property in the first <br />story results in less overall damage than for single story structures. Generally, expected annual <br /> <br />A-9 <br />