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<br />Overview <br /> <br />Water resource planners are charged in the plan formulation process to <br /> <br />evaluate a broad range of alternative flood damage reduction measures that <br /> <br />will provide flood damage relief for existing and future land use conditions. <br /> <br /> <br />The plan formulation process requires developing alternative means for <br /> <br />accomplishing performance targets and selecting from those alternatives the <br /> <br />ones which are the most attractive. This necessitates the systematic assess- <br /> <br />ment of the economic value of the proposed alternatives. In such cases it <br /> <br /> <br />is desirable that alternatives be compared quickly, with the comparisons <br /> <br />based on an adopted and consistent methodology. <br /> <br />Spatial analysis methods provide the mechanism for expedient and consistent <br /> <br /> <br />economic evaluation of alternative flood damage reduction measures. The <br /> <br />methods used include the evaluation of geographic information which has been <br /> <br /> <br />digitized and stored in computer files in digital form. Each geographic <br /> <br /> <br />data variable is encoded separately and a registered grid cell representa- <br /> <br /> <br />tion of each data variable is stored in a sequential grid cell record as a <br /> <br /> <br />part of the DATA BANK. <br /> <br />The geographic data variables that are used to perform the damage analysis <br /> <br /> <br />are: 1) topographic elevation, 2) reference flood elevation, 3) damage <br /> <br />reach delineation, 4) existing land use classification, and 5) alternative <br /> <br />future land use patterns. Each alternative analysis utilizing the DAMCAL <br /> <br /> <br />program results in the creation of an aggregated elevation-damage function <br /> <br />for each land use category at each damage reach index location. The func- <br /> <br /> <br />tions may be analyzed conventionally by damage-frequency integration methods <br /> <br />or used as input into more complex system formulation models, such as the <br /> <br />ATODTA-HEC-I linkage (described in Section 5 of this document). <br /> <br />The DAMCAL computer program accesses the geographic information stored in a <br /> <br />grid cell DATA BANK for the evaluation of 1) the existing land use condition <br /> <br /> <br />and 2) any number of future land use conditions or specific land development <br /> <br /> <br />proposals. A powerful analytical capability in the DAMCAL program is the <br /> <br />4-2 <br />