The Lawn Lake Flood

On Tuesday morning, Stephen Gillette set out on his route through Rocky Mountain National Park an hour earlier than usual. Mechanical issues meant that two of the A-1 Trash Co.’s trucks had been unable to make their rounds the preceding day, so he had set off before dawn to put a dent in the backlog. Around 6:15 in the morning, shortly after pulling into the Lawn Lake trailhead lot, he heard a roaring sound which he initially mistook for a jet about to crash. He realized his mistake when he looked for the source of the sound, but instead of seeing a jet he saw “…a ponderosa pine, limbs, bark and all, the whole thing, just sailing up, above the other trees…”.

He quickly backed toward the entrance, pulling his truck across the road to prevent a Michigan tourist from entering the lot. He exited the cab, racing to the emergency phone located at the trailhead entrance. Fortunately, the phone worked that day (it didn’t always), and at 6:26 the Park Service dispatcher heard Gillette, yelling to be heard over the sound of the roar, saying “A lake, a dam – something’s flooding!” After identifying himself, he informed the dispatcher that he’d barricade the road while waiting for the rangers to arrive.

Two park rangers arrived shortly, and within minutes of each other. The three quickly set about locking the Fall River Road gate, and barricading Horseshoe Park Road. By the time those tasks were completed, they were standing in rushing, muddy water up to their knees. It was clear to the Park Service that they were dealing with an emergency, but they didn’t yet know what exactly the emergency was, nor how severe.

As it happened, the source of the problem was the Lawn Lake Dam. The dam was most likely constructed in 1903, and had been expanded in 1931 to increase its capacity. Over the years, the makeshift road which had been built to aid in the dam’s construction had all but eroded away. By 1975, inspectors were forced to hike six miles each way in order to view the earthen dam. In 1975, the inspector recommended a more thorough examination once the snow melted, and in both '77 and '78, the dam was categorized as being in “fair” condition, and possibly in need of repair. Due in part to its inaccessible nature, no comprehensive examinations were done, and no repairs were made.

Shortly after 6 a.m. on July 15, 1982, the Lawn Lake Dam underwent a catastrophic failure, and for a brief period the Roaring River let the world know how it got its name. 30 million cubic feet of water tore through the landscape, ripping trees out by their roots, and sweeping tons of boulders and other debris along in its passing. Upon reaching the mouth of the valley at Horseshoe Park, where the torrent was able to spread out and slow for a bit, it left an alluvial fan covering over 40 acres.

That still wasn’t the end of it. Much of the water, mud and detritus rushed across the Horseshoe Park basin, merging with Fall River and backing up behind the Cascade Dam. Fortunately, this dam was able to withstand the added pressure, but the sheer volume meant that the dam was quickly overtopped, causing a secondary flood surge. Fortunately, much of the debris remained behind the dam, as this resultant swell poured through the town of Estes Park.

Floodwaters in the town reached between five and six feet in depth, and left two feet of thick mud in its wake as it hurtled through the town, joining the Big Thompson river on the far side. Elkhorn Avenue, Estes Park’s primary commercial strip, roughly paralleled Fall River, and sustained the bulk of the damage. When all was said and done, the flood did over 31 million dollars in damage to Estes Park alone, most of which wasn’t covered by insurance.

All things considered, it could have been significantly worse. Despite the event’s magnitude and force, only three people lost their lives; a lone hiker who had camped near the banks of the Roaring River (and who likely never knew what hit him), and a couple who returned to their campsite below the Cascade Dam, shortly before it overtopped. Given that the campground had been evacuated by the Park Service, it’s highly likely that the death toll would have been much higher if Stephen Gillette hadn’t set out on his route an hour earlier than usual that day.

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References

Dam! Flood!

Colorado's Deadliest Floods

Sadness in Sunshine