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ECONOMIC ANALYSIS D \"'....." rr~ .. ' ,.1 1.-1, I'''' \' ,r-,., " \ .... .,.._' .,- 1 'J /} 'I V L.\" "c.~l I' A...rY !i ':'...~ :\ /.~ J! 31 [) ;/r;,y J General A benefit/cost analysis was completed for the selected Flood Control Plan on Montrose Arroyo and Cedar Creek. The benefit/cost (b/c) ratio is used to compare the benefits provided by the project against the costs of building it. If the benefits exceed the costs (b/c) 1), then the project is economically feasible. If the b/c ratio is equal to or slightly less than one, the project may also be justified if the nuisance and inconvenience of repeated flooding make the project desirable to the community. Average Annual Benefits The benefits in this analysis inClude those realized directly from the reduction in damages due to the implementation of the proposed improve- ments. The proposed improvements are designed for a specific frequency flood. Any floods with a frequency higher than the design flood frequency oJ"'"' ,Jfl cause residual damages that the drainage improvements cannot protect. From the maps of residual flooded areas for floods equal to or greater than the design flood, these damages can be a.ssessed a.nd plotted against frequency as on Figures 6 and 7. The difference in this area under the two damages~rsus frequency curves is equal to the average annual reduction i.n damages. In determining the total annual benefits of a project, it is customary C\ to add to this amount an employment benefit of one percent of the construction . cost. Advanced replacement benefits are derived because some of the existi.ng culverts are old and would need to be replaced in a few years. The Flood Control Plan would provido all new structures \~hich would have a ] i Fespan