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<br />to both the contents and the structure (a different percent reduction could <br />be applied to each). <br /> <br />Since it is difficult to accurately estimate the damages reduced, several <br /> <br /> <br />runs are made for different percent reductions of the composite damage <br /> <br /> <br />fUDCtions to compute the break point necessary for the option to be cost <br /> <br />effective. The cost effective possibilities are then evaluated to deter- <br /> <br /> <br />mine whether or not the level of damage reduction can be reasonably achieved. <br /> <br /> <br />The evaluation of thia optional flood damage reduction measure is done by <br /> <br /> <br />directly modifying the composite stage-damage functions of the grid cell <br /> <br /> <br />damage potential to an appropraite index location. This permits the flood <br /> <br />warning option to be evaluated by itself or in combination with any of the <br /> <br />other nonstructural alternatives. <br /> <br />Permanent Evacuation of the Flood Plain. The evaluation of permanent <br />evacuation of the flood plain requires the spatial definition of the flood <br />area and removal of all designated land uses from that area. In this <br />option the reference flood is used for defining the flood plain in the same <br />manner as described in the computation of flood proofing to a target pro- <br />tection level and permanent evacuation of a flood plain is in the development <br />of the damage functions. Instead of a truncated elevation-damage function <br />(as shown in Figure 4-8d) , a no-damage (or a specified damage) function is <br />aggregated to the index location. <br /> <br />l <br />~ <br /> <br />Figure 4-9 (a reproduction of Figure 4-8c) is used to illustrate several <br />important aspectsre1ated to permanent evacuation of a flood plain area. <br />If the flood plain elevation computed for the grid cell is 423.0 feet <br />(Flood #1 of Figure 4-9) then the land use occupying the grid cell would <br />be removed and a no-damage potential (or a specified damage potential for <br />a grid cell exhibiting less damageable properties) would be aggregated to <br />the index location. If though, Flood #2 (a water surface elevation of <br />419.0 feet) is used to compute the flooded area to be evacuated, then the <br />grid cell is considered outside the flood plain of interest (grid cell <br />ground elevation above the computed elevation for Flood #2). An inspection <br /> <br />4-23 <br />