PROJECT #: CALCULATED BY: DATE:
D_0 Max Height of Pipe/Culvert 12 in
W_0 Max Width of Pipe/Culvert 12 in
Q Flow: 25-yr Storm Discharge 1.02 cfs
TW Tail water from 2 year storm 0.01 ft
Rip Rap Stone Size Calculations
q Unit Discharge = Q/W_0 1.02 cfs per foot
Option 1 if Scour Hole Depth, y = 1/2 D0 6 in
Apron Dimension Calculations
Minimum Bottom Width W_1=2 W_0 2.00 ft
Minimum Bottom Length L_1=3 D_0 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 d_50= 0.0125 q1.33 TW 6 in
Apron Thickness, TH = 2 × d_50 12 in
Option 2 if Scour Hole Depth, y = D_0 12 in
Apron Dimension Calculations
Minimum Bottom Width W_1=2 W_0 2.00 ft
Minimum Bottom Length L_1=3 D_0 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 d_50= 0.0082 q1.33 TW 15.4 in
Apron Thickness, TH = 2x d_50 30.8 in
Preformed Scour Hole
PLAN
Section A - A