Hydraulic Design of Highway Culverts - DOT On-Line Publications

Table 5 --Inflow Hydrograph, Example Problem (from SCS Tabular Method) (English)
0
-----
9
0.75
------
40
1.5
------
201
2.25
--------
70
0.125
-------
10
0.875
----------
80
1.625
----------
170
2.375
----------
60
3. Select Trial Culvert Size.
0.25
--------
11
1.0
-----
136
1.75
-------
140
2.5
-------
53
Time (hours)
----------------
Flow (ft 3 /s)
0.375
----------
137
13
1.125
----------
190
1.875
----------
120
2.625
----------
47
0.5
------
17
1.25
--------
220
2.0
------
98
2.75
-------
41
0.625
--------
28
1.375
----------
220
2.125
----------
82
2.875
----------
37
Enter the known information on the Culvert Design Form. For tailwater, use normal depth in the
downstream channel, from HDS No. 3. (Refer to Figure V-18, Culvert Design Form
for example problem.)
Three 36-inch CMP's are required to convey 220 ft³/s. Two 42-inch CMP's will convey the
routed peak flow. Two 36-inch CMP's might also work. Try two 36-inch CMP's and increase to
the larger barrel size if the routing calculations dictate.
Develop a performance curve for the two 36-inch CMP's (Figure V-19 and Figure V-20) and
enter the data on the Flood Routing Form, item 3 (Figure V-17).
4. Develop Elevation-Storage Relationship for Upstream Ponding.
The relief upstream of the culvert location is depicted in Figure V-21. Planimetric
determinations taken from the map are used to determine the elevation-storage relationship.
Enter the results in item 4 of Figure V-17.
5. Calculate the Storage-Outflow Relationship.
Using the elevation-discharge and elevation-storage relationships developed previously, use
Table 5 on Figure V-17 to calculate the storage-outflow relationship. The resultant curve is
shown in Figure V-22.
6. Perform the Storage Routing Procedure.
Perform the Figure V-17, perform the storage indication routing as shown. Directional arrows
are added in the example to indicate the calculation procedure.