A perfect storm could send debris hurtling down canyons and potentially damage property adjacent to the 416 Fire burn scar. To prepare for the worst-case scenario, La Plata County Office of Emergency Management is using a drone to get a bird’s-eye view of problem areas.
On Monday, Tom McNamara, emergency management coordinator, flew a drone with a camera attachment along Hermosa Creek to survey what kind of debris may become problematic in case it floods. He has done the same behind the Falls Creek subdivision and above the Lower Hermosa Campground.
“Primarily, there’s trees – old, dead fall that’s made its way into the creek,” McNamara said.
When trees are swept downstream by rushing water, they could become caught on bridges and dam the river, he said. If there is flooding, large debris could smash into structures and homes.
Despite warnings from the National Weather Service and emergency officials, no floods had occurred as of Monday afternoon near the burn scar. However, it’s just a matter of the right storm conditions in the right area, said Butch Knowlton, director for La Plata County Emergency Management.
“If it’s a dump in a short period of time, then that pushes a lot of stuff down in a hurry,” Knowlton said. “If it’s the way it’s been for the last few days ... then we do see a little bit of ash movement, but it hasn’t created any significant problems yet.”
Areas of specific concern include Dyke Canyon, Tripp Creek and the Hermosa Creek Drainage.
The goal of the drone work is to have a better idea of what lies upstream that is waiting to come down. Then, emergency officials can inform homeowners who are in the path of a potential debris flow.
When a big storm comes, they can also send emergency notifications and issue evacuations or pre-evacuations for areas expected to be hit hard by debris flows.
“If we get enough information, and understand what’s happening well enough, we should be able to be in a better position to keep people out of the way when something bad may happen or is happening,” McNamara said.
In addition to drone flyovers, emergency planners have existing flood maps, terrain modeling and geologic data such as soil types and slope gradient. Another good resource includes historic accounts from longtime residents who have experienced floods in the past.
Many residents remember the mudslides and debris flows that came after the 2002 Missionary Ridge Fire, which caused significant property damage to homes on East Animas Road (County Road 250), Florida Road (County Road 240) and the Vallecito area, among others.
In some cases, mud and rock broke through doors and flooded basements, garages and main living floors of homes.
“We have the experience,” Knowlton said, referring to the aftermath of Missionary Ridge. “We have the knowledge of what could occur.”
McNamara adds that a large part of the planning is finding areas that previously wouldn’t have posed a problem. Before the fire, hillsides might have been able to handle a lot of rain. Now, because they are void of vegetation, heavy rain will create mudslides or flooding.
The hope is that officials will be better prepared for danger, because with the drone imagery, they will be able to predict whether an area will flood or have large debris flows.
According to the National Weather Service, there is up to a 40 percent chance of thunderstorms Tuesday and a 20 percent chance Wednesday. Chances of storms decrease later in the week.
Whatever the weather does, there will be danger lurking on the mountain.
“The material is up there, the terrain is up there, the risk is up there,” Knowlton said. “It’s all solely dependent on the volume of rain that comes with each storm.”
rsimonovich@durangoherald.com