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<br />SECflON VII <br /> <br />BENEFIT COST ANALYSIS <br /> <br />EXPLANATION <br /> <br />The three alternatives-Improved flood plal'n, grass-lln~,d cl1snnel, ."nd <br />estimated optImum combInation-were deslgnllted by the local entities <br />and engIneering estImates to be the better choIces. ThIs was true <br />especially In"conslderatlon of the ope,ratlon and malrrtemance costs <br />of the other alternatives, whIch were clearly much hIgher. The deter- <br />mination of the optimal alternatIve, hClloJever, Is much more complIcated. <br />The principal reasons for this compl rcatlCl11 Include the, determlnati'on <br />of: <br /> <br />1. The most suItable alternative for each entity. <br /> <br />2. The best desIgn frequency In light of the damages resultln9 from <br />the frequency chosen. <br /> <br />3. metall design facts and cost estImates. <br /> <br />4. Intangible benefIts. <br /> <br />Because each of the th ree a lternat I ves cho!:en are to be eve I uated for <br />three design frequencies (10,25, and 100 year), there are nIne dIstInct <br />desIgn varlatlons to be considered for each Elntlty. Since there are <br />four entIties, 36 task Items had to be Inv!lstlgated b.ef.ore a vellld re- <br />cOf11T1endatlon could be made. <br /> <br />The present tool used to determIne the rel,altlve merit of the schemes, <br />,as requIred by the engineering agreement wIth the Urb"n Dndnage and <br />Flood Control District Is "Benefit Cost AnalysIs." The important con- <br />sideration In such an analysIs Is that all estimates must be mutually <br />consistent. In each evaluatIon, t~e Same basis for estimating prIces, <br />c:alculatlon methods, and economIc factors ''1as used. This contInuity In <br />calculatIon methods gave a reallstlc comparison between alternatives. <br />The comparison Is In the f~rm of benei'l't t,) cost ratl()s realized and <br />the probable annual costs. The ant1clpatad annual cost!! Include <br />average annual damage in dollars. This analysis will Indicate the best. <br />~:omparative alternative and Its appro~i'matl:...s~-ang,:.. It s~ould be <br />loealized that future development and Increased runoff from thiS develop- <br />ment will not occur for many years. Yet, the present worth computations <br />assume that such future development in the basin (and related flood siz- <br />Ing) already exist. <br />