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SCOPE OF URBAN STORM DRAINAGE The Public Concern Storm runoff in urban areas is of publi~ concern because the movement and temporary storage of stormwater inflects damage to public and private properties and disrupts normal community activities. It has been stated (1) that most flood damages in cities occur along tributary streams, often where drainage areas are even less than 100 acres. An estimate (25) is that $340 billion (replacement cost) worth of public and private capital investment is exposed to flooding by the'lOO year exceedence interval event, Local government has constructed $22 billion in drainage works for facilities that have cost between ,5 million and 2.5 million per square mile to construct, Another author (22) has put the economic consequences of storm drainage and urban flooding in context in the following: .Consider the following figures; direct economic costs of urban flooding are estimated by the Corps of Engineers at about one billion dollars per year which increases to at least 1.6 billion per yeariif unobserved upstream urban flood losses are accounted for, American cities spend at least 1/2 billion dollars each year for necessary drainage construction, Storm drains built in conjunction with new streets and highways require 1,4 billion dollars per year, Federal flood control construction adds a tidy construction sum also. It is easy to account for direct losses and expenditures amounting to mnre than 4 billion dollars per year. The current 4 billion rate projects to over 8 billion per year within the next 30 years, By then this nation will have spend at least 180 billion dollars for construction or flood losses." These figures, of course, include both stonn drainage and the traditional area of flood control, The distinction that will be made hereafter is that "storm drainage and urban flood control" refers to removal of excess water 3