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<br />oa1253 <br /> <br />CHAPTER II <br />SUMMARY OF PROJECT RESULTS <br /> <br />Technical Element of the Drainage Management Program <br />The development of an appropriate Technical element begins with a <br />description of the requirements for flood hydrology calculation in <br />urbanizing basins. Management of development-induced drainage impacts <br />requires an estimate of the growth-related changes to all aspects of <br />runoff response. The tools for estimating these changes are rainfall- <br />runoff models; models that predict the runoff response for some rain- <br />fall input, and for various levels of basin development. <br />These rainfall-runoff models can be classified into two categories: <br />Physically-based models and Conceptual models. The Physically-based <br />models simulate the physical processes involved in transforming rainfall <br />into runoff. They are supposed to be more accurate but their require- <br />ments (data, support personnel, and technology) make them relatively <br />time-consuming to initiate and expensive to support. The Conceptual <br />"black-box" models, on the other hand, can be initiated rather quickly <br />and are cheaper to support. <br />In order to recommend an appropriate rainfall-runoff model class, <br />the writers tested the predict~ve capability (both peak discharge and <br />hydrograph shape) of the more popular models within each category. <br />The data for these tests were taken from published reports. The tests <br />indicate that the Physically-based models (as a group) do not provide <br />significantly better runoff response predictions than the Conceptual <br />models. Further, the predictive capability of the Conceptual models <br />seems to be less sensitive to the model user than the predictive <br />capability of the Physically-based models. <br />