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instantaneous peak flows along Whiskey and Mercer Creeks upstream and downstream of the airport <br />property. Approximately 67 cfs is currently simulated to overtop the airport runway under existing <br />conditions during the peak of the 100 -year event. <br />Table 1. Annual Instantaneous Peak Discharges for Whiskey and Mercer Creek Near Bowers Field <br />r OdK nuw m Bno near main creeK cnannei <br />ExISTING CONDITION MODEL <br />The model was updated to represent existing site conditions by incorporating recent topographic survey <br />from Century West of the two airport runways and adjacent areas into the model terrain. The existing <br />condition model was then run to simulate the 2-, 10-, and 100 -year flood events'. Figure 2 shows 100 - <br />year model results indicating significant overland flow across Bowers Field and over runway 11-29. The <br />updated existing condition model provides a baseline for the alternatives analysis and evaluation of <br />project impacts. <br />WITH -PROJECT MODEL <br />A with -project model was developed to represent planned changes to the airport grading. These changes <br />include modifications to runway and taxiway extents and resurfacing that will be completed independent <br />of flood reduction measures. The with -project model was developed by merging a with -project terrain <br />surface (provided by Century West) with the existing condition model terrain. <br />1 2- and 10 -year flood simulation results are shown in Appendix A. 2- and 10 -year flooding would be primarily contained in. <br />channel or captured within existing airport drainage features. The 100 -year flood was therefore the focus of the alternatives <br />analysis. <br />WATERSHED I' f• 12 <br />Annual Instantaneous Peak Discharge° (cfs) <br />Return Interval <br />Whiskey Creek <br />Mercer Creek <br />(Years) <br />Upstream <br />Airport <br />Downstream <br />Airport <br />Upstream <br />Airport <br />Downstream <br />Airport <br />On Airport <br />Above Hungry <br />Junction Road <br />Below Bowers <br />Road <br />Above Hungry <br />Junction Road <br />Below Bowers <br />Road <br />Across Runway <br />Intersection <br />2 <br />81.7 <br />84.1 <br />14.8 <br />19.4 <br />0.0 <br />10 <br />160.4 <br />186.4 <br />77.6 <br />89.3 <br />0.0 <br />100 <br />524.4 <br />733.0 <br />293.3 <br />333.1 <br />66.8 <br />r OdK nuw m Bno near main creeK cnannei <br />ExISTING CONDITION MODEL <br />The model was updated to represent existing site conditions by incorporating recent topographic survey <br />from Century West of the two airport runways and adjacent areas into the model terrain. The existing <br />condition model was then run to simulate the 2-, 10-, and 100 -year flood events'. Figure 2 shows 100 - <br />year model results indicating significant overland flow across Bowers Field and over runway 11-29. The <br />updated existing condition model provides a baseline for the alternatives analysis and evaluation of <br />project impacts. <br />WITH -PROJECT MODEL <br />A with -project model was developed to represent planned changes to the airport grading. These changes <br />include modifications to runway and taxiway extents and resurfacing that will be completed independent <br />of flood reduction measures. The with -project model was developed by merging a with -project terrain <br />surface (provided by Century West) with the existing condition model terrain. <br />1 2- and 10 -year flood simulation results are shown in Appendix A. 2- and 10 -year flooding would be primarily contained in. <br />channel or captured within existing airport drainage features. The 100 -year flood was therefore the focus of the alternatives <br />analysis. <br />WATERSHED I' f• 12 <br />