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Work Sheet to Determine Peak Flow Rate from an Agricultural Watershed
Watershed Characteristics
-
Watershed size |
________ ha | ________
ac | -
Watershed
length | ________
m | ________ ft |
-
Elevation difference
over length of watershed | ________
m | ________ ft |
-
Average grade of watershed Elevation
difference ÷ Watershed length x 100 = (_______m ÷ _______m)
x 100 (_______ft ÷ _______ft) x 100 |
________ % |
-
Hydrologic soil group from Table 2.2 or OMAFRA Publication
29, Drainage Guide for Ontario | |
-
Hydrologic soil condition
from Table 2.3 | |
-
Runoff curve number from
Table 2.4 | |
- Choose the appropriate peak flow chart based on runoff curve number, ie. Table
2-5 to 2.11-M
(2.5-I to 2.11-I). Read watershed area across the top of the
figure and average grade along the left side. Enter the peak flow rates for the
appropriate return periods into the chart below.
| Storm return period | Flow
rate (m3/s) | Flow rate (ft3/s) |
| 2 years | | |
| 5 years | | |
| 10 years | | |
| 25 years | | |
Use the appropriate peak flows may then be used to design various structures
as outlined in Section 4.
For more information:
Toll Free: 1-877-424-1300
Local: (519) 826-4047
E-mail: ag.info.omafra@ontario.ca
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