SW5190201_2018-09-17 EC Diversion Ditch 2_7/16/2019

NOTE: This procedure is for uniform lio%v in cliaunel4 and is not to be
used for design of deeuergiaing deiices and may not he slid for larger
cltan nels.
User Input Data
Calculated Value
Reference Data
Designed By:
Tom Harrell Date: 9/17/2018
Checked By:
David Blevins Date: 9/17/2018
Company:
Development Engineering, Inc.
Project Name:
Cambridge Southeast Estates
Project No.:
1
Site Location (City/Town) Siler City
Chan nelMaterway Id. Diversion 2
Step 1. Select a liner material suitable for site conditions and application.
Determine roughness coefficient from manufacturer's specifications or Table
8.05e, page 8.05.10.
Liner material Jute Net
Roughness coefficient, n 0.022 Table 8.05e Table 8.05f
Permissible velocity, Vp
(ft/s) 2.0 Max. allowable velocity for bare soil
Step 2. Calculate the normal flow depth using Manumg's equation (Figure
8ASd). Clyeck to see that depth is consistent with that assumed for selection of
Manning's n in Fig re 8.05d, page 8.05.11. For smaller runoffs Figure 8.05d
is not as clearly defined. Recommended solutions can be determined by using
the Mamnag equation -
Step 3. Calculate shear stress at normal depth.
Step 4. Compare computed shear stress u^ith the permissible shear stress for
the liner.
Step 5. I£ computed shear is greater than permissible shear, adjust channel
dimensions to reduce shear, or select a more resistant lining and repeat steps
1 through 4.
Design storm 10-yr
Required Flow, Q (cfs) 2
Unit weight of water, y
(I b/ft3) 62.4
Channel slope, s (ft/ft) 0.02
Permissible shear
stress, Taud (Ib/ft) 2.00 Table 8.05g
N
L
a
S
L
-O
U
MW
>
_�
N
O
N
L
0
>
>
O Q
N O
N
Y
U
N
C
U
U U
C t6
t6 U
t6 N
t6 U
72
Trapezoidal U)
O
miE
I,
O
O`
Q
N
�a
N
=0
O
�Q
N
>
NL
>Q
L M
QQ
t6L
�Q
L.:
U)U)
L L
U)Q
Figure 8.05b
(ft)
(ft)
(ft)
(ft')
(ft)
(ft)
(ft/s)
(cfs)
(lb/ft')
Lu
UI wl
Lu d
3
2.0
1.50
11.00
9.75
11.49
0.85
0.022
8.59
� �
83.7
0
1.87
0