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benefits such as reduction in traffic, utilities, commerce, and other activity interruptions; public health hazards, stream quality enhancement, and general improvement of an area. A major benefit totally omitted in a dollars and cents category is the benefit of park and open space areas construction in conjunction with the gulch improvements, while the costs in- clude all costs associated with construction of the multi- purpose aspects of the project. However, the benefit/cost analysis has been a valuable aid in forcing the local juris- dictions and the District to choose the most economical design. CONCLUSIONS The unfavorable benefit/cost ratio for ~orth Sanderson Gulch also indicates that the benefit/cost analysis approach is wholly unsatisfactory for areas where little property damage exists but considerable nuisance is encountered~ The flows in North Sanderson Gulch simply are not great enough to cause the extreme property damages necessary to justify a project on a direct benefit/cost ratio. If the benefit/cost analysis theory were applied directly to all drainage facilities, a storm sewer would never be installed in any area since it seldom reduces direct property damage. The legal portion of the report deals with the problems of irrigation ditches and storage reservoirs and methods by which the public may acquire control of these and utilize them as assets to the overall drainage system. The majority of the drainage improvements on Sanderson and Weir Gulches may be justified on a benefit/cost ratio recognizing only the direct benefits due to reduction in flood damage potential. Additional fringe benefits simply enhance the benefits of the project. North Sanderson Gulch, North weir Gulch, and South Weir Gulch, must be lOOked upon as improve- ments necessary for the orderly development of the area. Implementation of the entire master plan will assure functioning of the total major drainage system during major storm occurrences. Current technology in the field of hydrology and hydraulics has given engineers the tools to forecast with reasonable accuracy both the magnitude and the effect of storm runoff on unbanized drainageways. The devastating economic and social impact which major floods may have on a community is unquestionable. However, the random fashion in which storms occur makes it impossible to forecast with certainty when a major flood will occur. Postponing major drainage improvements is gambling against the occurrence of a major flood. The design criteria developed for this study is specific to the individual gulches studied. It is the result of the input from the local entities involved ~nd the Urban Drainage and Flood Control District. The master plan presented in Volume II of this report in the form of plan and profile sheets is of sufficient detail to allow for segmental implementation of the plan with complete assurance that the individual portions will fit in with the overall project when completed. The master plan is sufficiently accurate to act as a basic plan for detailed construction plan and specifications preparation. Agencies must rem~in flexible in their uSe of the master plan, as cevisions will often be beneficial due to changing circumstances. In areas designated for flood plain ?Oning actual back"..ater profiles have been calculated to assure flood plain zoning areas that would be acceptable to the State water Conservation Board. The estimated costs presented are based upon present day con- struction costs and are tabulated in such a manner as to allow distribution of costs to the organization receiving the benefit from the particular improvements. The sequence of implementa- tion proposes methods by which th", irnproven\f)nts may proceed on d step by step basis as funds become available with the assurance that the most critical areas are completed first. -126- -127-