It’s not just in your head, this has been a wet spring.
May was the fourth-wettest for Boulder since 1872, according to city officials. Five and a half inches fell in the last 30 days. So how is the city’s stormwater infrastructure holding up to this influx of water? Are we on the brink of another 2013 flood event?
Not yet, but several more days of rain in a row could change that.
“Nothing we have experienced in this whole wet spring has been an issue for our systems,” said Joe Taddeucci, director of utilities for the City of Boulder.
Despite a similar vibe to 2013, when more than 18 inches of rain fell over five days to spawn deadly flooding, there are two major differences between that year and this one: duration and intensity.
Even though it feels like the precipitation has been incessant, the breaks between showers have been enough for rainwater to absorb into the ground or run through the city’s stormwater infrastructure before the next storm arrives.
And the intensity, at least so far, is manageable. Though this past weekend the rain seemed fierce, it was nothing compared to what summer thunderstorms sometimes bring. Taddeucci said while summer thunderstorms can drop an inch or two of rain on Boulder in an hour, the peak intensity this past weekend was just one-fifth of an inch an hour — with only an inch in total falling over the whole weekend.
But we’re not out of the woods yet, because Boulder’s ground is saturated. If the area gets one of those harsh summer thunderstorms before things have a chance to dry, that hourly inch or two of water will have nowhere to go but overland and into people’s basements.
“Everything that falls [now] is going to run off,” Taddeucci said. “If we started to get several days [of rain] in a row now like 2013, there’s no capacity for the ground to soak that up.”
Delayed flood mitigation projects
This year’s rain has brought to mind Boulder’s flood risk — among the highest in Colorado — and the flood projects the city has in the works. Just a few weeks ago, city council approved the next phase of a $43 million plan to mitigate flood risk in two major drainages moving southeast across the city. The project is one of more than two-dozen such plans in the works, totaling some $350 million, to be built over the coming decades.
In a perfect world, an update to the city’s stormwater infrastructure would already be well on its way, a decade after the 2013 floods destroyed hundreds of homes. Ideally, Boulder already would have the pipes and dams and streams able to handle massive flows of water. But because of the need for community engagement and a lengthy permitting process (among other factors), another flood might come before mitigation is in place to avert the worst repercussions, officials said.
“There can be a false sense of security, when we’re not experiencing a dramatic flood event right now, that we’ve got time to continue to debate and debate and debate,” Taddeucci said. “Finding a way to have good processes but getting these critical life-safety projects done expeditiously is the challenge we have as city staff.”
As was evident with the latest flood mitigation plan, there are always going to be passionate detractors, often people who live near the projects and are understandably opposed. (Look at CU South for another complicated example of how challenging it can be to break ground.)
But flooding is coming. A study published in Nature in 2021 found that climate change likely intensifies the frequency and severity of extreme inland flood events, while making more moderate ones less likely to happen. Tadeucci worries that community collaboration necessary to make Boulder more climate resilient is getting trickier, even as these more extreme events are expected.
“The intensity and the personal attacks on [city] staff have increased over the years,” Taddeuci said, noting a change in the 18 years he’s been with the city. “When you’re talking about people’s personal property or land use, it is very personal and emotional, and there have always been a tendency for personal attacks.
“I just think the frequency of that has increased over time.”