Changing Course

Bruce MacVicar wants cities to work with, rather than against, the natural flows of streams, rivers, and creeks. Through Global Water Futures, he and his team are coming up with innovative solutions.

Bruce MacVicar spends much of his time thinking about rivers in cities. As an Associate Professor in the University of Waterloo’s Department of Civil and Environmental Engineering, he leads the River Hydraulics Research Group, where he explores what happens to rivers and other waterways when we change the landscape around them.

“No matter how hard we may try to co-exist with rivers, human activity can have a huge impact on natural flows and regimes, as well as the ecosystems that depend on rivers to survive,” he says.

He points to the rise in urban flooding as an example.

“As we build cities, we change the volume of runoff that comes from the urban landscape during a rainstorm and we change its pathways. With climate change, the problem worsens. There are more frequent and more extreme storm events. Urban rivers can’t always sustain those flows, so one result is more frequent flood events in cities.”

Flooding can cause damage to property and human health, but there are other impacts that cities might not consider. In Oakville, Ontario, for instance, new modelling for climate change revised the city’s floodplain maps. “People found themselves living within those new borders,” MacVicar explains. “This changed the value of their homes and limited their ability to build and renovate. They began to sue the city for poor flood management.”

Urban areas are also continuing to grow, which is increasing the risk downstream, MacVicar says. Another impact that isn’t so obvious is extreme erosion. “Erosion is natural and is usually balanced by new sediment deposits,” he says. “But in cities, increased runoff leads to more water in the rivers that can erode streambanks. If we don’t notice and manage this erosion, it can undermine critical infrastructure such as bridges and expose sewers.”

MacVicar cites the 2005 torrential storm that caused such significant erosion that it damaged the Highland Creek Sanitary Trunk Sewer. This led to raw sewage flowing into the creek and required costly emergency repairs.

Anticipating change

In most cities, local governments (and, in Ontario, conservation authorities) are responsible for managing drainage networks, rivers, and channels. As time goes on, they must make investments to keep these built and natural services stable and functioning. But with such large systems to maintain in a new normal that demands adaptation, how do they know where to prioritize spending?

MacVicar’s group works with local partners to try to anticipate and mitigate damage. Sometimes they also try to restore environments that have sustained damage.

As part of Global Water Futures, one of the world’s largest university-led freshwater research programs, MacVicar and his team worked on a project with the Toronto and Region Conservation Authority and Credit Valley Conservation to understand, anticipate, and manage erosion as well as inform their watershed plans.

“As these local agencies spend money to rebuild channels and implement other measures, they need data to support and help prioritize their projects,” he says. “They want to know where these funds will have the highest impact and return.”

MacVicar’s research team wanted to help. They developed tools and algorithms to estimate stream power data (i.e., the rate of energy dissipation in a river) to make sense of what drives erosion and change in river systems. The open-source tool, called the Stream Power Index for Networks (SPIN), is freely available to practitioners on Github.  [NG1]

“It can be hard to come up with a diagnostic tool that can tell you where the erosion will occur,” he explains. “We can, however, predict the human reaction to a change, which is usually to try to stop the erosion from happening. We have shown good correlations of stream power where agencies have already put in erosion protection structures. This data can show us where they’ve had successes. It can also help them make the argument for tax dollars to be spent on measures and retrofits to moderate the urban river and creek flow regimes.”

Understanding how rivers flow

In addition to this tool, MacVicar’s team developed the Wobble Stone, which uses RFID (Radio Frequency Identification) to characterize the sediment response to a flood event.

“Measuring these responses is a tricky problem because sediment comes in various sizes and shapes, and there is a lot of variability in roughness, turbulence, and energy as sediment moves downstream,” he explains. “Rivers are dynamic systems. Animals and ecosystems rely on this natural movement as part of their habitat, but urban rivers can result in too much movement too frequently so that the rivers are unstable and the animals can’t adapt.

Furthermore, many of our solutions for erosion try to prevent any movement from occurring. “Our tendency is to build riffles and pools, using massive boulders that are designed to never move,” MacVicar says. “With this tracer tool, we’re trying to better understand how rivers function and to advance a nature-based approach that uses the movement of the sediment to rebuild damaged rivers, improve infrastructure resiliency and restore ecosystems.”

Working with the rivers

Over the past decade or so, MacVicar says, attitudes have changed on urban management and environmental restoration. He sees things continuing to change and move in the direction of respecting natural flows – that is, working together with rivers, rather than against them.

Through GWF, he’s had the chance to work with several partners who are already thinking this way, including an Indigenous community-led project in British Columbia that is trying to restore habitats to improve fish spawning.

“For this project, we had a student put in a bunch of tracers to characterize the environment before they put in the spawning gravels,” says MacVicar. “We are using the tracing and numerical modelling to help our partners come up with the strategy that is most likely to succeed.”

Collaborating and adapting

This work – and being part of GWF’s diverse network of researchers and partners – changed the way MacVicar thinks about much of his research, he says.

“Taking a process-based and adaptive approach to restoration means we can think of techniques that are also relatively less costly and less invasive or problematic. We can monitor and adjust the strategy over time.”

Without partners, he adds, there is the question of whether the research will ever change anything in the real world. “It doesn’t matter if you develop the tools – it matters that they solve real challenges, and that people actually use them.”

MacVicar says: “I like to think we are helping make change. And, with better decision support systems, the people who are most directly impacted can feel empowered by the data. GWF helped us advance these ideas. Together we’re helping to protect and restore natural assets.”