2026-02 Offsite Stability NOAA 24-hr D 25-Year Rainfall=6.68", P2=4.04" Prepared by Dynamic Engineering Printed 2/10/2026 HydroCAD® 10.20-8a s/n 08640 © 2025 HydroCAD Software Solutions LLC Page 9
Summary for Subcatchment 16S: Study Area Roof (Imp)
Runoff = 0.46 cfs @ 12.19 hrs, Volume= 0.059 af, Depth= 6.44" Routed to Link 191 : Study Area Basin A (Total)
Routed to Link 19L : Study Area Basin A (Total)
Runoff by SCS TR-20 method, UH=Delmarva, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs NOAA 24-hr D 25-Year Rainfall=6.68", P2=4.04"
Area (ac) CN Description
0.110 98 Roofs, HSG A
0.110 98 100.00% Impervious Area
Tc (min) Length (feet) Slope (ft/ft) Velocity (ft/sec) Capacity (cfs)
0.8 207 0.0100 4.50 1.57 Pipe Channel, A-B 8.0" Round Area= 0.3 sf Perim= 2.1' r= 0.17' n= 0.010 PVC, smooth interior
0.8 207 Total, Increased to minimum Tc = 10.0 min
Subcatchment 16S: Study Area Roof (Imp)
2026-02 Offsite StabilityNOAA 24-hr D 25-Year Rainfall=6.68", P2=4.04"
Prepared by Dynamic EngineeringPrinted 2/10/2026
HydroCAD ® 10.20-8a s/n 08640 © 2025 HydroCAD Software Solutions LLCPage 10
Summary for Subcatchment 18S: Study Area WQ MTD A-110 (Imp)
Runoff = 2.55 cfs @ 12.19 hrs, Volume= 0.327 af, Depth= 6.44"
Routed to Link 18L : Study Area Study Area WQ MTD A-110 (Total)
Runoff by SCS TR-20 method, UH=Delmarva, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.05 hrs
NOAA 24-hr D 25-Year Rainfall=6.68", P2=4.04"
Area (ac) CN Description
0.610 98 Paved parking, HSG A
0.610 98 100.00% Impervious Area
Tc (min) Length (feet) Slope (ft/ft) Velocity (ft/sec) Capacity (cfs) Description
0.6 55 0.0302 1.62 Sheet Flow, A-B Smooth surfaces n= 0.011 P2= 4.04"
1.3 297 0.0035 3.68 4.52 Pipe Channel, B-C 15.0" Round Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.011 Concrete pipe, straight & clean
1.9 352 Total, Increased to minimum Tc = 10.0 min
Subcatchment 18S: Study Area WQ MTD A-110 (Imp)