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<br />. -----... <br /> <br />- <br /> <br />and a sanitation function. This distinction is important because <br />when proposed UDFC projects are being evaluated, it must be shown <br />that anticipated benefits exceed costs, The benefits from natural <br />hazard protection clearly will be distinct from those provided as <br />an environmental management service, and should be counted up separately, <br /> <br />The environmental management services provided by urban drainage <br /> <br />systems have formerly included only consideration of runoff quantity <br />but, as pointed out several years ago by the ASCE Urban Water Resources <br />Research Council [1], and more recently by Condon [5], quality aspects <br />are crucial, especially in advanced stages of urbanization. This <br />report is basically concerned only with quantity but the role of UDFC <br />projects in quality management must soon be recognized. As of now, <br />urban drainage systems do not usually contain provisions for control <br /> <br />and treatment of stormwater, This is expected to change rapidly, <br /> <br />however. <br /> <br />, <br /> <br />Types of Evaluation Problems <br />There are really two general types of evaluation problems; those <br />for personal use and those leading to arguments for convincing others. <br /> <br /> <br />Problems related to UDFC fall into both of these categories, but it <br /> <br /> <br />is convenient to assume that they are all of the latter type such that <br /> <br /> <br />information remains completely objective, <br /> <br /> <br />The life cycle of an urban drainage and flood control (UDFC) <br /> <br /> <br />project extends from the first perception of a need through planning, <br /> <br /> <br />programming, budgeting, design, construction and operation. If the <br /> <br /> <br />project completes this cycle it will have cleared many socio~political, <br /> <br /> <br />technical and economic hurdles. The project should not reach the <br /> <br />18 <br />