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<br />Technology has been developed and applied by Corps of Engineers, <br />Hydrologic Engineering Center, which accesses geographic information <br />stored in a grid cell data bank for an integrated evaluation of flood <br />hazard potential, flood damage and environmental effects of 1) existing <br />land use condition, 2) alternative future land use conditions and 3) <br />specific land development proposals. A powerful analytical capability <br />in the spatial flood damage analysis is the ability to evaluate the <br />nonstructura1 alternatives of 1) flood plain management policies. 2) <br />flood proofing alternatives which may include raising structures, ring <br />levees or the addition of flood proofing materials to structures. 3) <br />permanent evacuation of structures in the flood plain 4) temporary <br />structural protection and content removal in response to flood warning <br />disseminations. and 5) combinations of the above. These alternatives <br />may be evaluated in terms of providing a target protection level (such <br />as protection from the lOO-year frequency flood) or as providing uniform <br />1and'use category protection (for instance flood proofing industrial <br />structures four,feet above ground elevation). <br /> <br />The geographic data variables that are used to perform the analysis <br />are: 1) topographic elevation. 2) reference flood elevations, 3) damage <br />reach delineations. 4) existing land use classification, and 5) alter- . <br />native future land use patterns. The output for each spatial flood <br />damage analysis is an aggregated elevation-damage function for each land <br />use category at each damage reach index location; These functions may . <br />subsequently be analyzed conventionally by damage frequency integration <br />methods or used as input into more complex system formulation models. <br /> <br />The objective of the nonstructura1 evaluation procedures developed and <br />presented herein is the systematic and consistent development and modifi- <br />cation of elevation-damage relationships corresponding to specific non- <br />structural flood loss reduction measures. The procedures described <br />include the automatic generation of the damage functions for selected <br />land use patterns by processing selected spatial gridded data variables, <br />and the modification of these damage functions for specified nonstructural <br />alternatives based on uniform structural protection criteria or a prescribed <br />level of protection. These concepts were applied for the Trail Creek <br />watershed located near Athens in northeast Georgia. <br /> <br />DAMAGE FUNCTION DEVELOPMENT <br /> <br />General Approach.--Methods of computing the flood damage potential of <br />a stream reach requires the development of elevation-damage functions at <br />selected damage reach index locations throughout the system. The e1evation- <br />damage functions are then integrated with hydrologic flow-frequency and <br />flow-elevation data to compute the expected value of annual damages. Damage <br />reaches are defined to allow capturing economic and hydrologic variation <br />that oCcur in the reach; ,Elevation-damage relationships are developed for <br />individual structures and the associated value of the contents. The <br />structure functions lire aggregated to an index location and adjusted to <br />account for the slope of water surface profiles throughout the damage reach. <br /> <br />2 <br />