Water management - soak it in

NRU
April 13, 2016
By Geordie Gordon

Lake Simcoe Conservation Authority is proactively working to effect a paradigm shift from centralized water management systems for capturing rainwater in urban areas to a more decentralized approach through various on-site interventions. This will result in fewer negative impacts on the natural
environment.

Dillon Consulting associate Ian Roul told participants at the April 12 OPPI event that the water cycle is acutely impacted by development and it is difficult if not impossible to mitigate under the current stormwater management regime. There are ways to do things differently using low-impact development.

“One of the really interesting things about low-impact development ... is that it requires [the participation of] all disciplines. It’s not strictly an engineering question, it’s not strictly a science question, there’s a real element of community planning,” he said.

Low-impact development is an umbrella term for interventions using natural features, such as green streets, which use cub cuts to allow the stormwaterfl ow to enter tree wells, bioswales and green roofs.

The Lake Simcoe Region Conservation Authority has proposed amended regulations. These would require new developments and redevelopments to be designed to accommodate the first 25 mm of rain on site. Roul said this change means that 93 per cent of all rain would be dealt with on site. This represents a five times increase in the volume of water required to be dealt with on site.

Speaking with NRU following the event, Roul said that the proposed LSRCA regulations are in part a response to increased flooding events and degraded aquatic ecosystems.

“The Lake Simcoe Conservation Authority is taking the first crack at increasing those regulations ... but the Credit Valley Conservation and Toronto and Region Conservation Authority are likely to follow suit shortly after,” he said. “We’re kind of at a key juncture where municipalities like Mississauga and Toronto are implementing their own [low-impact development] programs, and conservation authorities are implementing regulations to support those programs ... We’re right in that period of time when it’s becoming mainstream.”

In her presentation, TRCA CTC source water protection program manager Jennifer Stephens gave an overview of the Credit River, Toronto and Region and Central and Lake Ontario Source Protection Area (CTC) Source Water Protection Plan that came into effect December 31, 2015. Stephens said that the plan contains policies that ensure municipal water systems are protected into the future, and that the focus now is on ensuring the policies are being implemented correctly.

In speaking with NRU, Stephens and CVC planner Colleen Bonner said there is an opportunity to integrate source water protection policies and low-impact development, although it
will vary from area to area.

“There is that fi ne balance of making sure you’re returning the groundwater to the ground when you’re doing a new development. It really depends on the situation of where the development is happening,” Bonner said.

Stephens said that there are policies in the CTC Source Water Protection Plan that require, where there is a threat to water quantity, site plan and subdivision developers to return as much water to the ground as they are taking out.

“In that type of situation, it’s perfect for low-impact development,” she said.

Design is critical to the success of low-impact development, Roul said. Marrying function and aesthetics in the public realm, a sense of ownership can result, thus relieving concerns about the ongoing maintenance of green infrastructure. As an example a bioswale-which can remove silt and pollution from surface runoff - can also function as an amphitheater.

Low-impact development is by its nature decentralized, and not only complements natural features but can be incorporated into existing uses, such as parks, in ways that won’t interfere with their primary use.

Roul likens the concept of getting buy-in for low-impact development to that of the 3Rs of recycling. He suggests promoting the 3Ss of low-impact development-Slow it down, Spread it out and Soak it in.

“If we can do that with our water, which is the complete opposite of conventional stormwater systems—that efficiently transport to a centralized location-we’ll ... start to see a return back to less impacted watercourses,” he said.