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<br />e <br /> <br />e <br /> <br />e <br /> <br />7.0 COMPUTATION OF ECONOMIC LOSSES <br /> <br />Thp m~thnrl~ prp,~nted for aS5e~5i~9 ecoQowic losses sre PQ~@d gR t~e best <br />available information considering the degree of detail warranted, ease in <br />application, general applicability and availability of data. <br /> <br />Potential economic losses may result from: <br /> <br />(1) Loss of pavement and embankment. <br />(2) Interruption of normal traffic flow. <br />(3) Damage to surrounding property due to backwater. <br />(4) Structural damage including scouring of foundations. <br /> <br />Subsequent parts of this manual contain suggested methods for assessing the <br />various economic losses. To illustrate these methods, the following <br />example problem will be used throughout the discussion. <br /> <br />7.1 Example Problem <br /> <br />A crossing of Row Creek is proposed. The hydrologic and hydraulic calcula- <br />tions have been accomplished and the alternative bridge length and embankment <br />heights selected. Only one of the alternative designs, a bridge length of 440 <br />feet and embankment height elevation 153, is used to illustrate the economic <br />loss evaluation procedures. The reader should recognize that the economic <br />loss evaluation procedures would have to be repeated for each alternative design <br />to complete the LTEC design decisionmaking process. Additional data are <br />presented as needed for the various economic loss assessment procedures. <br /> <br />7.2 Embankment Damage <br /> <br />Flood flows which overtop bridge approach embankments for sustained periods <br />of time may result in erosion of shoulders and fill material and loss of <br />the p~vement surface. When such damage occurs, economic losses due to <br />traffic interruption and the need to replace the fill and pavement result. <br />In order to assess these losses, the mechanics of erosion must be known. <br />Unfortunately embankment erosion has not been studied on a broad scale and <br />the existing literature can only supply limited information on the subject. <br /> <br />Some experience is available from highway agencies concerning the <br />duration and depth of overtopping which will cause erosion. Figure 7.1 <br />is based on this experience. Users are encouraged to develop information <br />on roadway damage due to overtopping for application in evaluation of <br />the economic losses to embankment and pavement. <br /> <br />39 <br />