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<br />001343 <br /> <br />14 <br /> <br />Similar regression equations can be developed for other regions <br />provided the requirements for Conceptual models listed in Table II-l <br />are available. The development procedure consists of extracting unit <br />hyorographs fronl regional rainfall-runoff records for watersheds with <br />various percentages of development. The unit hydrograph characteristics <br />(peak runoff rate, time-to-peak, base width, etc.) are then equated to <br />watershed physiography by multiple regression analysis. <br />As an alternative to this regression approach, the urbanization- <br />induced changes of watershed response can be evaluated by a novel <br />utilization of the n-linear reservoir conceptual model reported by <br />Wittenburg (10~). He proposed two conceptual linear reservoirs in <br />parallel -- one that accounts for the impervious area of the watershed <br />and one .that accounts for the pervious areas. Once the parameter for <br />each of these conceptual reservoirs has been determined, the runoff <br />hydrograph from watersheds with various percentages of development <br />can be determined by dividing it into pervious and impervious areas <br />and then routing the proportionate amount of rainfall excess, for a <br />specific recurrence interval, through the respective res~rvoirs. The <br />concept appears viable but the parameter estimation for each of the <br />conceptual reservoirs is considerably more difficult than the <br />parameter estimation of single linear reservoir theory. <br />Unlike the linear conceptual models, the quasi-linear conceptual <br />rainfall-runoff model uses characteristics of the input rainfall event <br />to define the response transformation. That is, the quasi-linear <br />model regression equation is a non-linear function -that relat~s the <br />characteristic(s) of the linear transform function (Nash model, linear <br />reservoir model, etc.) to the rainfall characteristics (rainfall <br />