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<br />001341 <br /> <br />12 <br /> <br />to identify the hydrologic consequences of a specific development. <br />The table reveals that there is no universal hydrologic response for- <br />mula for estimating the effects of urbanization on stormwater runoff <br />characteristics. <br />The listed works are not without merit, however. They all <br />substantiate the notion of increasing peak discharge with increasing <br />urbanization. The peak discharge for urbanized conditions ranges from <br />l.ti to e times that for natural conditions for frequent events (mean <br />annual flood), and from 1.0 to 3.0 times for the rare events (100 year <br />flood). With the exception of uoehring's investigation (32), the <br />studies further indicate that the effects of urbanization on rare <br />events are significantly less than on frequent events. In addition, <br />each of the studies presents a method for evaluating the effects of <br />urbanization and identifies the data requirements for that method. <br />In the absence of universal applicability of the results, the real value <br />of the studies becomes the methods and the data requirements they <br />suggest. <br />A number of the techniques presented by the investigators listed <br />in Appendix A could satisfactorily be used as prediction models for <br />urbanizing basins. The techniques fall into one of two categories: <br />"Conceptual" rainfall-runoff models and "physically-based" rainfall- <br />runoff models. This categorization is not sacred and at least one <br />author (lOb) has questioned the existence of two separate categories <br />due to the numerous natura,l phenomenon approximations and parameter <br />estimations (i.e., conceptualization) required for physically-based <br />models. The writers feel, however, that in addition to the different <br />data requirements, the philosophy of approximating the physical <br /> <br />, <br />