If the design objective is to meet and provide peak flow control for storm events, it is necessary to plan beyond the 1:100-year peak flow, and instead plan for the new norm of a 1:1000-year flood event. Planning for the appropriate peak flow is crucial to building climate resilience and meeting the demand over the full lifecycle of the infrastructure. If an inadequate peak flow formula is used it could result in significant additional costs to the City if it has to repair or tear up failing infrastructure to rebuild and increase capacity before it has reached its end-life. “Even a 1000-year return period has a 5% risk of being equalled or exceeded in a 50-year period.”
The Report indicates that “the anticipated influence of climate change on precipitation is steeped in uncertainty with future projections ranging from a minimal increase to almost a 250% increase”, and yet the stormwater planning only ranges from a 1:5 to a 1:100-year flood event. The Report admits that “this range represents a significant challenge to the municipality to understand and integrate into its planning decision making process”.
It is also important to emphasize the importance of planning for a warming climate by building resilience into whichever alternative/s are chosen. In this vein, planning should be based on at least a 1:200-year storm event, and preferably a 1:1000-year flood event for true resilience to climate change.
These Public Information Centre panels are very high level, so at this time there isn’t too much to comment on; however, it is important to consider the Chelmsford Wastewater Treatment Facility in this assessment.
Watershed and subwatershed studies should include water quality and water quantity considerations to help maintain and enhance natural freshwater systems, including fisheries and aquatic habitat. These considerations should be guided by commonly accepted and held principles, including an ecosystem-based approach, a landscape-based analysis, cumulative effects, the precautionary approach, adaptive management, and sustainable development.
What are the goals and objectives of this study? There is very little information about the subwatershed study, but instead appears to be primarily designed to manage stormwater run-off to prevent flooding and development impacts.
VRS is recommending that a portion of the funding be assigned to a Master Watershed Study for the Vermilion River Watershed. This study would take a big picture perspective, and consider the cumulative effects that development, stormwater runoff, and wastewater and mining effluent are having on the Vermilion River. This would better inform potential mitigation measures required for the subwatersheds contained within it.
The Vermilion River Stewardship (VRS), is grateful for this opportunity to comment on the draft Terms of Reference (ToR) for the Ramsey Lake Watershed Study; however, the short deadline for comments has made it challenging to make a thorough review. VRS requests that a minimum comment period of 30 days be provided in all future requests for public feedback. This would allow for an adequate opportunity to review and prepare a comprehensive and meaningful submission.