Most of the time, St. Vrain Creek winds through Longmont as a lazy, gurgling stream.
During the lower flows of mid-summer at Dickens Farm Nature Area, it’s easy to forget the creek’s potential power. On an August afternoon, a group of kids splashed in the slow-moving water, its channel lined with native grasses and flowering shrubs.
“We're in the range of 50 to 100 (CFS—cubic feet per second) today,” said Josh Sherman, a civil engineer in Longmont’s Public Works and Natural Resources Department, eyeballing the stream’s flow. “We're designing a channel, though, that for flood flows is 15,500 CFS, so several orders of magnitude larger.”
Ten years ago a massive flood inundated Front Range communities from Boulder to Fort Collins. Within hours it transformed the St. Vrain from a babbling stream to a freight train of water. Communities throughout Northern Colorado, from small mountain hamlets to cities on the plains, saw their local creeks and rivers swell, becoming unrecognizable in both scale and their capability for destruction.
Dickens Farm Nature Area, a park that invites residents to cool off in the St. Vrain, lies just downstream of the city’s bustling downtown. During the floods of 2013, this park contained a string of empty gravel pits that filled with water and threatened to breach their banks. Torrential rains in the foothills and mountains above Longmont swelled the creek, and sent its waters rushing through town, spilling over bridges and destroying roads in the process.
Longmont was split in two.
“At one point, we really only had one roadway crossing the St. Vrain,” Sherman said. “You can believe it was a bottleneck trying to get from one side of town to the other.”
In the time since, the flood’s damage has been repaired. But even now, a decade later, projects to make sure the city is prepared to weather the next big storm are still underway.
The 2013 floods
The event started on September 11, 2013. A large mass of extremely moist air moved into Colorado and parked itself right above Boulder and Larimer counties, hovering over foothills and mountain communities where flash floods are a regular occurrence. This was on a different level than a normal flash flood. The National Weather Service warned of “biblical rainfall amounts.”
The storm hung in place for two days and dropped the equivalent of a year’s worth of rain in some areas. Parts of Boulder County recorded upwards of 18 inches of rain over the course of a few days. Because of where the rain fell—up in the mountains and foothills—it kicked off a multi-day flooding event.
By the time the rain stopped and the water began to recede, it was clear the flood had taken a devastating toll. The 2013 Front Range floods still stand as one of the costliest natural disasters the state has faced in recent history. Nine people were killed. Damage estimates approached $4 billion. More than 19,000 people were evacuated. 3,000 people were rescued, some by helicopters that flew into mountain communities after people became stranded when roads were destroyed. About 28,000 homes were damaged or destroyed.
The effects were widespread. Many communities were particularly hard hit, including Estes Park, Lyons, Evans, Longmont, Boulder, Glen Haven, Drake, Pinewood Springs and Kersey. The damage wasn’t contained to one area. As the water rushed down the mountains, it tore up roads, bridges, sewer lines and irrigation infrastructure, sending a slug of murky, roiling water as far as the Nebraska state line.
From recovery to resilience
In the years that followed, Longmont walked the familiar path of a community reeling from a natural disaster.
First came the recovery phase. That meant fixing roadways, reconnecting utilities, ensuring residents made it back home safely. Then came the long-term challenges. Efforts included everything from learning how to live in harmony with a flood-prone stream to taking stock of the emergency response and strengthening community connections to withstand the next natural disaster.
Rather than just rebuild and then wait for the next giant storm, Sherman said the city took the opportunity the flood provided to rethink its relationship to the St. Vrain. Since the flood, he has led projects associated with Longmont’s Resilient St. Vrain project. Using a mix of federal, state and local funds, the city has invested in deepening and widening the St. Vrain and improving the trail system along its course to turn it into a more flood-friendly waterway.
“This project is the prime example of resiliency, where we're making additional improvements above and beyond what existed previously to try to be more resilient to those future disasters,” Sherman said.
At Dickens Farm, that meant installing drop structures to slow the stream and direct its flow. Elsewhere along the stream the city purchased private property to give the creek room to fill without causing damage to buildings during higher flows.
Longmont voters have approved two bond measures to cover a portion of the project’s cost. Estimates for the entire project range from $120 to $140 million. Work initially began downstream in Longmont at Sandstone Ranch and has worked its way upstream over time. Projects at Izaak Walton Nature Area and near Hover Road have yet to start construction, Sherman said.
Outside city limits
Floods don’t follow political boundaries. Because the 2013 flood was so widespread, it forced all levels of government to work together on recovery and coordinate rebuilding infrastructure to better handle future floods. To keep the city of Longmont safe from the next deluge, infrastructure improvements needed to happen in both the urban core and in rural pockets upstream.
“When the flood happened, it came through this park and damaged it pretty significantly,” Boulder County Parks and Open Space planner Justin Atherton-Wood said as he walked along a path in Pella Crossing, a county-owned park west of Longmont. “Out here in the rural part of the county, we have the chance to let those flood waters sort of spread out a little bit.”
Flood infrastructure looks different in a rural setting versus a more urban one. Atherton-Wood and his teams spent time reconfiguring public parks like this one after the flood to better accommodate future ones. Here, it meant changing the landscape to give the creek’s floodwaters an easier path to follow. The park’s ponds are now better connected. The land between them swoops downward, like the mouth of a funnel, so that when and if they fill with flood water, the ponds can slow down the creek’s flows instead of threatening to breach, Atherton-Wood said.
“It just creates that roughness that slows down the stream and also allows for those grade changes to happen in a way that's controlled,” he said.
The St. Vrain, like many Front Range waterways, performs a few functions. It delivers irrigation water to farmers, provides drinking water to cities, and acts as a key feature of the surrounding ecosystem. Balancing all of those things while engineering the landscape to better handle a flood can be tricky, Atherton-Wood said.
“So how do you let a creek do what it wants to do, and do that in a way that's somewhat controlled so that the kind of damage we saw in 2013 doesn't happen in the future?” he said.
Social infrastructure plays a role
Rebounding from a natural disaster isn’t just about the things we build with concrete and earth. Longmont’s social fabric played a role as well. For Marta Loachamin, that was revealed when immigrant families—many of whom don’t speak English—were unable to quickly get emergency information during the flood or find translators to help them access state and federal resources after the fact. She sees the layer of community networks as just as important as the built landscape.
“I do believe we have an ability as people to work in the social infrastructure in a way that really could allow first responders and community members to be more connected, to get to resources first,” Loachamin said.
She felt the flood’s effects personally. During the flood, she and her children were evacuated. Her home’s basement eventually filled with water.
“Rain still is traumatic for me, when it wakes me up at night,” Loachamin said. “It just takes me back there and I think it does to so many people.”
She learned about the emergency notifications through friends and neighbors, rather than through official channels.
“That was also my first experience of the emergency systems that do exist and don't necessarily reach everybody,” Loachamin said. “Because then I realized, ‘Oh, I haven't ever opted into this program.’”
Loachamin, now a Boulder County commissioner, led the Longmont's Resiliencia Para Todos project. It was an attempt to map out all of these potential gaps in the local social infrastructure. In a series of focus groups and interviews, the project’s facilitators found that fractured community connections, language barriers, and gaps in media communication all contributed to vulnerable populations feeling pushed aside during the emergency itself and the recovery afterward.
As a result, the city invested in identifying and supporting "cultural brokers," trusted community members who could connect disaster victims with resources. But Loachamin said Boulder County and Longmont still have a ways to go when it comes to creating true resilience to future disasters.
“It's the physical infrastructure and that social piece, that there's a tug of war until we decide that we're going to really create these systems to bring everybody together,” she said.
And while the built infrastructure for Longmont’s flood mitigation plan should be wrapped up in the next few years, Loachamin said efforts to tighten the community’s social ties need to be ongoing to withstand whatever natural disaster comes next.
