On July 31, Scott Tampa, the president of the Cutthroat Chapter of Trout Unlimited, which serves the south Denver metro area for the national conservation nonprofit, was fishing the South Platte River in Cheesman Canyon. Also casting that day: his wife, Meg Renton, and Pat Dorsey, co-owner of the Blue Quill Angler and local legend in the fly-fishing guide community. The trio hit the water around eight in the morning, and by the afternoon, they noticed the western sky darken. They decided to make their way back to the Gill Trail, a five-mile out-and-back managed by the Pike-San Isabel National Forest and Denver Water that provides access to the canyon—one of the most productive and beloved stretches of trout-fishing water in the country.

“We thought it was a typical Colorado storm that would blow right through,” Tampa says. Instead, the deluge lasted around an hour and dropped an astonishing 2.5 inches of rain into the canyon and Denver Water’s Cheesman Reservoir upstream, according to a Denver Water spokesperson.

Tampa, who had been wading across the river when the first drops fell, didn’t make it 40 yards before his group was forced to take shelter in a rock tunnel. “It was coming down so hard that you could see the water cutting grooves into the hillside,” he says. “And they grew and grew and grew.”

The river, which had been crystal clear minutes before, turned to mud. “We couldn’t believe how strong and powerful the storm was,” Tampa says. “We were in there going, ‘How are we going to even get out of here?’” When the storm finally subsided, the group discovered that mudslides had covered parts of the Gill Trail. In other sections, the trail was simply gone.

On Tuesday, Dorsey posted a photo on his Instagram of an area inside the canyon known as Rainbow Pool and Peanut Rock, which showed a slide of tons of decomposed granite filling half the width of the river. “A few people however, said it’s normal,” he wrote. “I beg to differ…this is not normal, natural, etc. One of the best [fishing] holes in the canyon is destroyed, not to mention many, many more.… The destruction is mind-boggling.”

The same day, Tampa watched yet another storm roll in on the horizon over Cheesman Canyon as he recounted the previous day’s drama over the phone. Rivers tend to heal themselves, he says, but he doesn’t expect Cheesman Canyon will be fishable for a while. Not only will access be a considerable challenge until the Gill Trail is repaired—and a survey of the damage will have to be completed before Trout Unlimited and its partners at the U.S. Forest Service and Denver Water know what that even means—but the newfound sedimentation can affect the trout. It not only clouds the water, it can choke fish; smother and kill insect larvae, harming the food chain trout depend on; and absorb sunlight, heating water temperatures to unhealthy levels for the fish. The USFS did not immediately respond to a request for comment.

Tampa’s Trout Unlimited chapter had already been working with the USFS and Denver Water to study river sedimentation caused by erosion of the Gill Trail, he says. The plan was to rate each section of the path from green to red—good to bad—to help identify where maintenance and upgrades were most needed. “We knew there were a lot of green stretches [before the storm],” Tampa says. “From what I saw yesterday, I don’t think there are any more green stretches.” And now that the vegetation has been ripped away, making erosion easier, there will likely be more damage each time the skies open. “Until somebody can get back there and stop these big areas [of exposed earth] that are just flowing right into the river, it is going to continue like that with any rain that’s coming down,” he says.

The mudslide in Cheesman Canyon. Photo by Scott Tampa

On Wednesday, Tampa, Dorsey, and Chris Steinbeck, another guide at the Blue Quill Angler, walked the canyon to assess the damage. They came across tree limbs, leaves, and other debris blocking the flow. “We saw many slides of gravel into the river, some large enough to alter the course of the river,” Tampa says. “We did not see any fish in the river in these areas. We talked with a few fly fishermen to see if they had caught anything, and the unanimous response was ‘nothing.’”

Initially, Tampa hoped Denver Water would release more water from the Cheesman Dam to flush some of the sedimentation out of the canyon, but the storm increased flows so much that Denver Water was actually forced to decrease releases so that it didn’t overrun the waterway, according to a Denver Water spokesperson. As of press time, the utility did not respond to a follow-up about what plans it has, if any, to help the river’s trout population.

Tampa and the Cutthroat Chapter of Trout Unlimited are still waiting to hear back from the USFS about how they can help with the recovery. There has already been some movement: The statewide chapter of Trout Unlimited has reached out to Tampa to start coordinating volunteers and assistance as soon as there’s something to do. “This is going to take a lot of people,” Tampa says. “So anybody that has ever had the fortune to go back into that canyon and knows how beautiful it is back there, we’re going to need their help.”

Nicholas Hunt
Nicholas Hunt
Nicholas writes and edits the Compass, Adventure, and Culture sections of 5280 and writes for 5280.com.