Restoration and soil mitigation work is underway in Horse Gulch, a popular network of hiking and mountain biking trails east of downtown Durango.
The work began in late April and is expected to continue for at least several more weeks, although an exact end date has not been determined. The work has caused the temporary closure of Half Ridge Trail, which is accessible near the base of Horse Gulch Road via a shorter trail.
Trail work in Horse Gulch aims to mitigate soil erosion and will extend the popular Half Ridge Trail’s total length by the time the project is completed. Additional work includes the realignment of the Half Ridge and Powerline trails and rerouting Flame Out Trail to tie into the new alignment.
Resource restoration work is also planned for a segment of Horse Gulch that consists of informal trails that have soil erosion.
Once construction is complete, the trail will be just over a mile long, said Amy Schwarzbach, natural resources manager with the city.
When Durango acquired the piece of land in Horse Gulch that contains the Half Ridge Trail, the trail had technically already been established, she said. The trail was used as a fire break or an access road before it was purchased by the city, but despite its use today as a hiking and mountain biking trail, it wasn’t built with those uses in mind.
The trail is wide by mountain bike standards – as wide as 25 feet in some areas – because of erosion issues, she said. Though the trail remains a good fire break to this day, the soil became hard and compacted because it used to be a route for vehicles, which made it more susceptible to erosion from rainfall. Rain washed much of the soil away, leaving rough rocks with erosive channels between and underneath them.
“Fluffy soil and plant matter absorbs the energy of a raindrop,” Schwarzbach said. “It’s pretty incredible science.”
But when soft soil and plant life aren’t present to absorb the impact of rainfall, water carves erosive channels through the earth, she said.
The soil gets washed away and all that is left are rocks or “ankle-twisters,” as Schwarzbach calls them.
“Even after the rocks were exposed, erosion didn’t stop,” she said. “Underneath the rocks you could see erosive channels and the rocks had kind of fallen in like a gully or a ditch. And then trail users looking for solid footing were walking on either side of the rocks.”
She said the rocks are challenging to navigate on a mountain bike and unpleasant to walk over.
Durango Trails is using a mini-excavator to build drainage features that will allow water to flow off the trail into vegetated areas, she said.
When Half Ridge is rebuilt, hikers and mountain bikers will enjoy great views to the north from atop the ridge and a sweeping view of Horse Gulch Meadow beyond the first few switchbacks on the way down, Schwarzbach said.
“If you work your way down the trail or up the trail, you look out across the new Durango Mesa,” she said. “And so it’s just got incredible views. And then if you drop closer to the trailhead at the bottom, you see views across downtown Durango and over to Hogs Back.”
The Half Ridge Trail project and trail realignments started April 20 and are expected to continue for at least several more weeks, Schwarzbach said.
An area near the Horse Gulch trailhead is undergoing resource restoration by Durango Parks and Recreation in partnership with Southwest Conservation Corps, which is also lending some help with Half Ridge Trail.
Schwarzbach said most of that restoration area came into the city’s possession when it acquired Durango Mesa Park last year. The area is crisscrossed with “socially made,” or unofficial, trails, which have undergone similar erosion problems as Half Ridge Trail.
A massive rain that occurred several years ago caused mud to flow down Horse Gulch Road, wash through the parking lot at the trailhead and empty into the Animas River, which is a U.S. waterway, she said.
“So taking care of how much dirt flows that way and down into the Animas River is part of why we want to mitigate erosion but still provide great trail experiences,” she said.
A similar erosion mitigation project could focus on an unnamed cliff trail near the Horse Gulch trailhead in 2023, Schwarzbach said.
The trees in Horse Gulch have enough to worry about without having their roots uncovered by erosion, Schwarzbach said. A tree having its roots uncovered by eroded soil faces one more stress factor that can harm its health. Trees are already dealing with drought and beetle infestations.
The extended drought caused by shifts in temperature is affecting the health of trees, she said; their immune systems are weaker and they are also dealing with the blight of spruce beetles.
Eroded dirt and soil that ends up in the Animas River can also be a detriment to fish and other aquatic life that live beneath the water’s surface, she said.
The city’s plan is to close trails that were not purpose-built with drainage to improve soil health in order to let the trees surrounding those trails have time to heal.
From May 2021 through April 2022, Horse Gulch had a total of 84,000 trail users with 7,000 average users monthly, Schwarzbach said.