Plan addresses risk of storm flooding in Revelstoke

An interview with City of Revelstoke engineer Mike Thomas about the new Stormwater Management Plan

Last week, the City of Revelstoke held an open house for its Stormwater Management Plan. Almost nobody attended, including myself.

The plan, which is still in draft form,  looks at the city’s stormwater pipes, which transport rain and snow melt from city streets out to the Columbia River. It makes a number of recommendations, with the main ones being to undertake more detailed study of the system, and to upgrade seven sections of pipe throughout the city, at a cost of about $3.6 million.

I spoke to Mike Thomas, the city’s director of engineering, about the plan, which was produced by WSP/MMM Group. Here are the highlights of our conversation:

Alex Cooper: Why does the city need stormwater management plan?

Mike Thomas: With climate change impacts, changing storm conditions, more intense storms, we want to make sure the systems that have been installed in the past are going to service into the future. We wanted to identify areas where the capacity of the existing system might be limited.

AC: How many kilometres of stormwater pipes does the city have right now?

MT: I don’t have the answer on the tip of my tongue. The formalized system is really only through Lower Town, Downtown and Southside. There’s very little formalized drainage in Arrow Heights and not a lot in Columbia Park. The focus of this study was more on looking after the major flows. The recommended upgrades out of the report are focused on the major trunk systems on the areas we have undersized pipes.

AC: What’s the state of the existing system?

MT: We’ve got some large diameter pipe systems that go under the city that we don’t have a good understanding of the condition of those pipes. That’s one of the recommendations of this report, to start documenting the actual condition of it. We’ve really looked at capacity, not condition of the pipes at this point.

AC: The plan makes seven recommendations for stormwater upgrades. Why are those needed?

MT: Through the modelling the consultants did on the existing system, they ran a five-year storm through it and a 100-year storm through it and they looked at how these pipe systems respond in the model to those storms. They looked ahead at how our storms are expected to change under climate system. These identified pipes are sections that didn’t perform well through that simulation.

AC: What is expected to happen in the future?

MT: Summarizing it, it’s warmer wetter winters and drier, hotter summers, but with more intense storms than we would have seen in the past. That impacts our storm system. Generally, the faster water reaches the storm system, the more likely it’s going to be overwhelmed.

Some of the other recommendations we are looking at are onsite protections and reducing the amount of water that reaches the storm system, so putting it back in the ground instead of running it off straight into a catch basin. If we can do that, maybe we can mitigate the effects of climate change and our existing systems would last longer.”

AC: The plan calls for about $3.6 million in capital upgrades – can the city afford that?

MT: We haven’t put a hard and fast timeline on that… Do we have the money to do it? That’s where council has to make a decision on the priorities of the community. I would suggest in a lot of cases we wouldn’t dig up the storm system unless we need to repave the road at the same time, and we would look at what other infrastructure needed to be done at the same time and try to do it as a package.

This report really informs the priority for stormwater, but that may not line up with the priorities with roads and sewer. All of this information need to be combined and prioritized for each road section, not just for the individual asset class for stormwater.

AC: Is the city at risk of a catastrophic flood event if these upgrades don’t happen soon?

MT: It’s a difficult question because in the few years I’ve been here we haven’t experienced a major storm. Calgary experience a major storm a few years ago. Kamloops has experienced major storms recently and had some serious flooding. These upgrades would limit the impact of those sort of storms on the areas. One of the things we’re lucky to have is we have the Columbia River system right there. We can move water away fairly quickly if we have the right size of pipes. We can limit the risk to properties. If we have good infrastructure we can limit the risk of dangerous flooding conditions if we have the right infrastructure in place to get that water away.