PROJECT #: CALCULATED BY: DATE:
Design Parameters
D0 Max Height of Pipe/Culvert
W0 Max Width of Pipe/Culvert
Q Flow: 25-yr Storm Discharge [F4]
TW Tail water from 2 year storm
Rip Rap Stone Size Calculations
q Unit Discharge = Q/W0 0.17 cfs per foot
Option 1 if Scour Hole Depth, y = (1)/(2)D0 6 in
Apron Dimension Calculations
Minimum Bottom Width W1 = 2 W0 2.00 ft
Minimum Bottom Length L1 = 3 D0 3.00 ft
Minimum Top Width (max side slope of 3:1), 5.00 ft
Minimum Top Length (max side slope of 3:1) 6.00 ft
Median Stone d50 = (0.0125q1.33)/TW 4 in
Apron Thickness, TH = 2 × d50 8 in
Option 2 if Scour Hole Depth, y = D0 12 in
Apron Dimension Calculations
Minimum Bottom Width W1 = 2 W0 2.00 ft
Minimum Bottom Length L1 = 3 D0 3.00 ft
Minimum Top Width (max side slope of 3:1), 8.00 ft
Minimum Top Length (max side slope of 3:1) 9.00 ft
Median Stone d50 = (0.0082q1.33)/TW 4 in
Apron Thickness, TH = $ 2x $ d50 8 in