Table 8.1 – Comparison of Windsor Airport and New MTO IDF Curves
| 100-Year Return Period | |||
|---|---|---|---|
| Time (mins) | Windsor Airport Intensity (mm/hr) | MTO Updated IDF Intensity (mm/hr) | Difference % |
| 5 | 228.5 | 212.4 | -7 |
| 10 | 161.5 | 158.4 | -2 |
| 15 | 142.6 | 136 | -5 |
| 30 | 98.9 | 102.4 | 4 |
| 60 | 62.1 | 66.5 | 7 |
| 120 | 35.1 | 40.5 | 15 |
| 360 | 14.5 | 16.8 | 16 |
| 720 | 8.3 | 9.5 | 14 |
| 1440 | 4.6 | 5 | 9 |
Table 8.2 – Comparison of MTO Drainage Management Manual, 1997 and New MTO IDF Curves
| 100-Year Return Period | |||
|---|---|---|---|
| Time (mins) | MTO District 1 - South of Dresden Intensity (mm/hr) | MTO Updated IDF Intensity (mm/hr) | Difference % |
| 5 | 235 | 212.4 | -10 |
| 10 | 165 | 158.4 | -4 |
| 15 | 135 | 136 | 1 |
| 30 | 100 | 102.4 | 2 |
| 60 | 64 | 66.5 | 4 |
| 120 | 43 | 40.5 | -6 |
| 360 | 14 | 16.8 | 20 |
| 720 | 9.1 | 9.5 | 4 |
| 1440 | 4.5 | 5 | 11 |
A preliminary evaluation of the 30 percent design of drainage elements was undertaken to estimate the impacts of the new IDF curves on peak flows and water surface elevations. Although for the drain realignments and crossings, it was demonstrated that the criteria for freeboard could not be met; no changes to the design storms for these elements were completed. This was based on an assessment of flood risk potential by HMQ, given that these elements were designed to convey the Hurricane Hazel Storm Event.
The evaluation of the performance of the stormwater management ponds with the new MTO IDF curves demonstrated that none of the seven ponds were capable of meeting the criteria for freeboard. However, with the exception of Ponds 4 and 6, all ponds were capable of controlling post-development peak flow rates to pre-development rates. As such, as directed by HMQ, only Ponds 4 and 6 were redesigned to provide the additional required active storage. Refer to the Lennon Drain Stormwater Management Report (PIE/Dillon Consulting, 2012) for the design of Pond 4, and the McKee Drain Stormwater Management Report (PIE/Dillon Consulting, 2012) for the design of Pond 6.