Thompson Creek Flood Study Report - City of Peterborough

Thompson Creek Detailed Flood Reduction Study
City of Peterborough
Table 4.5.2
Peak Flows for Thompson Creek for 6 Hour AES Return Period Storms
Location
Area
(ha)
Peak Runoff Rate (m 3 /s)
2 Year 5 Year 10 Year 25 Year 50 Year 100 Year
#1 (Thompson Dam) 0 0.100 0.100 0.100 0.100 0.100 0.100
#2 (Pond Outlet) 11.15 0.168 0.219 0.267 0.315 0.385 0.426
#3 (Proposed Crossing) 38.32 0.333 0.490 0.630 0.813 1.044 1.170
#4 (Armour Road) 48.72 0.430 0.657 0.831 1.055 1.365 1.526
#5 (Otonabee River) 66.32 0.620 0.954 1.227 1.517 1.917 2.156
Table 4.5.3 shows the peak flows at the same locations for the one hour AES storm .
Table 4.5.3
Peak Flows for Thompson Creek for 1 Hour AES Return Period Storms
Location
Area
(ha)
Peak Runoff Rate (m 3 /s)
2 Year 5 Year 10 Year 25 Year 50 Year 100 Year
#1 (Thompson Dam) 0 0.100 0.100 0.100 0.100 0.100 0.100
#2 (Pond Outlet) 11.15 0.173 0.255 0.334 0.424 0.514 0.588
#3 (Proposed Crossing) 38.32 0.301 0.504 0.697 0.930 1.201 1.414
#4 (Armour Road) 48.72 0.363 0.633 0.915 1.194 1.547 1.824
#5 (Otonabee River) 66.32 0.699 1.137 1.530 1.973 2.372 2.721
As indicated by the tables, the one hour distribution generates the highest peak flow at
all locations for all return periods. Hence these flows (as indicated in Table 4.5.3) were
adopted as the “design flows” for the return period events for Thompson Creek.
Detailed simulation outputs from Visual OTTHYMO are included in Appendix H.
The calculated peak flows were input to the HEC-RAS model of Thompson Creek to
calculate the corresponding water levels. Table 4.5.4 shows the water levels for the 1 in
100 year storm. Mapping of the corresponding flood line is described in Section 4.6.1.
Water levels for the 1 in 2 year to 1 in 50 year storms (which are all less than those
indicated in Table 4.5.4) are presented in Appendix I with the HEC-RAS outputs.
4.5.2.2 Volume Events for Flood Vulnerability Mapping
Table 4.5.5 shows the calculated peak flows for Thompson Creek for future land use
conditions (described in Section 4.4.1.1) for the six volume based events required by
the Terms of Reference. Flows are indicated for the one hour AES storms at the
locations on the creek indicated on Figure 4.4.2. The one hour storm was found to give
the highest set of peak flows. A comparison between Tables 4.5.3 and 4.5.5 shows that
the peak flows from this set of events exceed the 1 in 100 year peak flow for all storm
with a volume of 60 mm or more and that the 120 mm storm generates peak flows
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