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I I I I I I I I I I I I I I I I I I I 4.7.2 Modeling Reslllt~ The results of the hydrologic modeling of future conditions for each subbasin as well as specific locations along the major drainageway are presented in Table 4.6 and Table 4.7. A graphical representation of the discharge profile along the major drainageway is provided in Figures 4.3 and 4.4 for the Godding Hollow and Tri-TownBasins, respectively. For comparison with existing condition modeling results, future condition flood hydro graphs at selected locations are presented in Appendix B. Within the Godding Hollow Basin, the impact of future development on the stormwater runoff generated during the major storm events is not significant. This is largely attributed to the placement of on-site detention ponds that limit the releases during the lOa-year storm event to the 100-year existing condition runoff. It is likely, however, that an increase in the peak flows within the major drainageway will occur even with the on-site detention facilities. Delayed peaks resulting from the attenuation of the stormwater runoff may result in a minor increase in the peak discharge in Godding Hollow when compared to the existing conditions. Although the peak discharge may not increase significantly, the volume of the stormwater runoff will increase thereby significantly increasing the duration of flooding: For the Tri-Town Basin, the impact of future development on the stormwater runoff generated during major storm events is significant in that a reduction in the peak discharges is evident. In comparison with the results associated with the existing conditions, the peak discharges within the major drainageway are reduced, thereby reducing the potential flooding. The reduction in the peak discharge data and the associated flooding is attributable to the placement of on-site detention ponds that limit releases to the 2-year existing condition runoff in the upper portion of the basin. In general, the flood problems presently experienced within the Godding Hollow Basin will be slightly exacerbated with future development. As stated previously, the flood peaks will be increased as a result of the placement of on-site detention ponds which may extend the duration of the peak discharge. For the Tri-Town Basin, the flooding problems will be reduced with future development within the basin. The placement of on-site detention facilities with 2-year existing condition release rates reduced the flood peaks in the major drainageway by as much as 2,000 cfs, While flooding problems may still persist at several locations due to the capacity of the existing facilities, the severity of the problems is reduced. Furthermore, the extent of the improvements necessary to further reduce the flooding is also reduced by the placement of the on-site detention facilities with 2-year existing condition release rates. T:\OPEMCoweidO)\coweldOJ.tnl rpt.wpd 4.22 September 8, J 999