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<br />A fonTI similar to figure 2.2 can be used to document the assessment or <br />screening process. The form includes the three types of losses: traffic <br />related, roadway, and backwater. Under each type of loss are the factors which <br />will be used to assess that loss. For example, traffic losses are assessed <br />indirectly by detennining the number of vehicles which use the structure and <br />evaluating how frequently, if ever, they will be delayed or detoured. This is <br />done by estir,lating the overtoppi ng flood probabil ity for the alternative with <br />the smallest structure and fill. If the roadway carries a large volume of <br />traffic and will be frequently overtopped, the LTEC design process should be <br />used. Similarly, the other losses can be estimated or calculated and compared <br />to the thresholds. The thresholds must be established through the use of the <br />LTEC design process; noting the values at which a factor yields little or no <br />response. <br /> <br />If the assess~ent indicates that the LTEC process is appropriate, the encroach- <br />f"ent can be further screened by estimating the magnitudes of the various risk <br />costs and comparing these to the annual capital costs. This comparison is <br />illustrated in Table 2.1. The procedure is based on an initial trial design <br />which may be selected using traditional design concepts. The economic losses <br />(roadway, traffic related, and backwater) are determined for the one design and <br />their relative impact determined. If one or more of the economic losses are <br />relatively small compared to the other losses, they ~ay be assumed constant or <br />ignored when analyzing the other alternatives. <br /> <br />4 <br /> <br />e <br /> <br />. <br /> <br />e <br /> <br />. <br /> <br />e <br />