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WEST SENECA - POST DEVELOPMENT E_App E_Post-Development Model_REV 2 NY-West Seneca 24-hr S1 25-yr Rainfall=3.84" Prepared by Labella Associates Printed 7/26/2026 HydroCAD® 10.20-6a s/n 09581 © 2024 HydroCAD Software Solutions LLC Page 44 Summary for Subcatchment PS-7: Runoff = 11.45 cfs @ 12.15 hrs, Volume= 0.886 af, Depth= 1.91" Routed to Reach DP-1 : Design Point Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs NY-West Seneca 24-hr S1 25-yr Rainfall=3.84" Area (sf) CN Description 242,510 80 >75% Grass cover, Good, HSG D 242,510 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.5 100 0.0450 0.20 Sheet Flow, Grass: Short n= 0.150 P2= 2.20" 5.3 271 0.0148 0.85 Shallow Concentrated Flow, SCF Short Grass Pasture Kv= 7.0 fps 0.2 20 0.1500 1.94 Shallow Concentrated Flow, SCF Woodland Kv= 5.0 fps 14.0 391 Total Subcatchment PS-7: Hydrograph Runoff 12 11.45 cfs 11 NY-West Seneca 24-hr S1 25-yr Rainfall=3.84" 10 Runoff Area=242,510 sf 9 Runoff Volume=0.886 af 8 Runoff Depth=1.91" Flow (cfs) 7 Flow Length=391' 6 Tc=14.0 min 5 CN=80 4 3 2 1 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Page 511 of 1174