The Waldo Canyon Burn Zone At Risk For Flooding
A team of scientists has been examining damaged land to understand the flood risks associated with the fire. KRCC’s Andrea Chalfin recently traveled to Cascade to see the science behind the assessments, and to understand why flooding becomes such a risk after a fire.
Residents in and near the Waldo Canyon burn areas have been encouraged to purchase flood insurance if they don’t already have it. New federal legislation recently signed into law waives a 30-day waiting period for some new policies to take effect.
"We’re in the Waldo Canyon burn area, and behind us is national forest and below us is HWY 24. The reason why we’re standing right here is it’s burned all around us, it’s burned high severity above us, and below us, we’re concerned about increased water flow and sediment coming down toward these communities."
Hydrologist Dana Butler is one of two team leaders for the Burned Area Emergency Response, or BAER, team. They’re looking at the health of the Pike National Forest after the Waldo Canyon fire erupted nearly three weeks ago.
"Specifically, in the burned area, we have a changed condition. We had a lot of fire come through here as you can tell. Vegetation has burned, there’s a lot of leaves and duff and litter that’s usually on the ground that kind of intercepts the rainfall and stops it from moving down slope. Now we have this changed condition, we’re concerned about increased flooding, or perhaps sediment moving down slope."
The changed condition isn’t just about burned plants and trees. It’s also about the dirt, and how the burned plant life affects it. Brad Rust is one of two soil scientists tasked with sampling areas across the 18 thousand scorched acres.
"There’s vegetation for instance, this oak, little scrub oak here, it has oily waxes in it, and when it burns, those fuels and vapors are pushed down into the soil, and depending on what texture the soil is, if it¿s real course like this, then it pushes down into the soil maybe two to four inches deep. That causes like a water repellent layer."
Rust digs into the dirt to gauge the severity of the issue.
So I’ll dig open the soil, like this and I just want to go to the first four inches, and just take a look. See what’s going on. Now, we already see something happening right here. It’s moist to about three to four inches, and then it gets suddenly really dry. So that’s cluing me in that there’s a problem that we’re going to have in this soil. So I want to do is drop some water on it and see if it beads up, and how long does that take to penetrate into the soil. If it’s less than ten seconds, then everything’s ok. But if it’s up to two minutes or more, then we’ve got a hydrophobic or water-repellent situation.
So the more rain that falls and the harder it does, the quicker the dirt on top becomes saturated. Once water reaches the repellent layer, the topsoil begins to erode. That means increased debris flowing down slope, but also the potential for clogged culverts. Rust considers this particular area lightly to moderately burned, and says it will take about a year or two before the repellent layer dissipates.
While the BAER team works to establish burn severity on forest land, Jonas Feinstien with the Natural Resources Conservation Service, or NRCS, says they use that data to help determine what private property is most at risk.
"so when the fires come and those increased flows, sediment and debris come down the mountain, we don’t want it washing through the front door of a house, or through the backdoor of a school, washing route a major egress route for a community, a highway. The list goes on and on."
Once the assessments are made as to which properties face imminent threats, the NRCS works to lessen risk and potential damage. In an emergency situation such as this, the cost is covered by the NRCS and a sponsor, typically a local government entity.
Standing near a pooled flow of ash and mud, BAER team co-leader Dana Butler says in the meantime, the most important thing residents can do is remain vigilant of the weather.
"These flood flows, they can take out a vehicle, they can take out kids, they can take you out, so please just go to higher ground if there’s a warning from the National Weather Service."
The BAER team released its Burn Severity Map on Wednesday. It’ll be used to assess what areas are most at risk, and will be included in a report with recommendations to help minimize the impacts of flooding. The full report is expected Monday.