This was definitely one for the record books. On Monday, September 9, a gentle rain began falling over the Front Range (the eastern slope of the Rocky Mountains from Fort Collins in the north to Colorado Springs in the south). Many people welcomed it. Although it had eased considerably this year, we were still in the grip of a prolonged drought that was killing trees and contributing to terrible wildfires. The steady rain, brought in by a cold front, seemed a blessing.
As it happened, there were two large tropical storms pumping moisture into the atmosphere, one over Mexico’s Gulf coast, and one over Mexico’s Pacific coast, and this moisture was being funneled northward over the Rockies. There was also a front over the Midwest, generating easterly winds. When these winds met the Rockies they were pushed upward. As the air rose, it cooled, encountered all that tropical moisture, and caused the rain.
This kind of pattern is so common along the Front Range that it has a nickname: an upslope. It can occur up to a few times a year and is notorious for causing legendary dumpings of snow. However, there was something unusual about it this time. The Jet Stream—that river of high-speed wind in the upper atmosphere—had split into two streams, leaving the sky over Colorado in a gigantic eddy between them. The high pressure to the west didn’t budge, the low to the east kept sending wind, and the moisture from two oceans kept shooting up the middle.
After three days of soaking rain, the intensity began to pick up. By this time, soils were saturated. The Weather Service started issuing warnings for areas that had been affected by fires in recent years, of possible landslides and flash floods. Still, those were limited areas and we were used to hearing such warnings. Our townhouse is well away from those zones.
Karel and I were at an open mic in Lafayette on Wednesday night, when it really started raining hard. The event was well-attended; no one was especially worried. It’s very common in Colorado for a small, intense storm to blow through and unleash a deluge. These are usually isolated, fast-moving, and short-lived. What we didn’t know was that it was raining like this along the entire Front Range, and that the storm wasn’t moving at all.
We started getting “push alerts” on our phones, every hour or so. 6 p.m.: Expect heavy rain and big puddles (localized flooding). Duh. 7 p.m.: Flash flood advisories for the burn areas. Tell us something we don’t already know. 8 p.m.: Flood advisory on South Boulder Creek. Hmmm, OK, still far away and easy to get around it. 9 p.m.: Flash flood warning for Left Hand Creek. Whoa, that’s in the other direction, we seem to be sandwiched between two storm cells. 10 p.m.: South Boulder Road closed due to flooding. This was followed quickly by some of the other east-west roads south of town. That’s it, time to go home. We took a northerly route and had an uneventful trip, except for plowing through one really big puddle.
We found our home snug and dry, so we turned on the news. The weathercasters were wide-eyed and stuttering. Instead of spending their rain and blowing away across the prairie, the storms were doing something weird: they were growing fast, and they weren’t moving. The storm and flood warnings had been extended to the north and south. Reports were coming in from the mountains of steady downpours that had already been going on for hours and kept getting worse. Our phones continued to receive alerts, but now, instead of warnings for a particular creek, they were for all watersheds on the Front Range. For several rivers, including Boulder Creek, instead of advisories, there were evacuation orders. Flash floods were crashing down the canyons, wiping out roads and bridges as they went.
Behind our house, water comes at us from two different directions. Just out the back door the Boulder and Whiterock irrigation ditch shunts water from Boulder Creek to farmland to the northeast. It’s an old, tree-lined ditch that looks like a pleasant little stream. A few meters upstream, the ditch crosses over Goose Creek via a small aqueduct. Goose Creek is just a trickle most of the time, but it has been known to swell to 6000 cubic feet per second. It flooded twice in the 1950s, causing damage to the hospital.
When I bought the townhouse in 2004, I got a good price in part because the backyard was a big, noisy construction zone. The City had just removed a couple dozen trailer homes that were sitting in the flood plain, and construction was just beginning on a project to cope with potential flooding, build a bike path, and restore the cement-lined water chute to a more natural wetland environment. The commotion was a nuisance for a couple of years, but the result was a lovely park, a well-connected trail that allowed me to walk or bike anywhere in town, and the townhouse was no longer in the floodplain.
Around midnight, I donned some raingear and went out back to see how things were holding up. The park was flooded, possibly 3 meters deep in places, but the water was flowing smoothly, below the three bridges from Folsom to 28th Street, with room to spare. It would have to double or even triple in volume before it would be a threat to us. Unless there was a debris dam ready to burst somewhere upstream, we would be OK.
We spent an uneasy night listening to sirens and the sound of rushing water. In the morning, it was still raining, and the emergency warnings were still streaming in. There had been a flash flood on the North St. Vrain River. Lyons was completely cut off. A landslide had wiped out part of Jamestown. The feared wall of water on Boulder Creek had dissipated before hitting town, but there was general flooding throughout the downtown area and neighborhoods on every side of us, and 4000 people had been evacuated. Karel found a picture of the storage complex where we have a unit, with the buildings standing in a few feet of muddy water, so we assumed our books, files, and winter clothes were submerged in muck. Dozens of bridges were washed out and almost every major road was closed. Some of the smaller dams had collapsed, and more were in danger.
We started checking in with friends and family. Everyone we could reach was OK, but there were some we couldn’t contact. My sister had had an exciting night at her home in the mountains. Surface run-off had overwhelmed the culverts and drainage ditches and started to flood the lower level of the house, but they had gone out in the darkness with shovels and managed to divert most of the water away from the house.
Sometime after 2 a.m., Suzanne had gone back in to check the latest news. They announced the flash flood warning for the St. Vrain at about 2:30. She hesitantly dialed Phyllis (the owner of the beautiful house on the St. Vrain where we had our wedding celebration last year). It was a ridiculous hour to call, but either she was awake and running for higher ground, or she needed to be.
We don’t know the full story yet. Phyllis answered, but sounded drowsy. “Do you know what’s happening?” Suzanne asked. She didn’t seem to. “You need to get up. Check the news. Look outside. You may have to get out of there.” Phyllis replied, but still didn’t sound fully awake. “Phyllis, this is important. You really need to wake up and see what’s going on.”
Phyllis later told Suzanne that “some woman called” and woke her up. The first thing she noticed when she stood up was that the floor of her second-story bedroom was tilted. She woke her daughter, Marissa, and a friend that was spending the night (John was out of town). They put on raincoats and grabbed the two cats. When they opened the front door, water came gushing in. In the early-morning darkness, they waded into chest-high, rushing water and tried to make their way to higher ground. It took them an hour to cross—at one point, the trees to which they were clinging were uprooted, torn out of their hands, and swept away, and they had to scramble back. At last, they somehow made it across the new channel that the river was cutting through their front yard. A neighbor heard their calls and helped get them to the emergency shelter in Lyons.
When day broke on Thursday the situation in Boulder had settled down a bit. By that, I mean that everything was still flooded, but the water wasn’t getting any higher. It was still raining hard, and the threats remained. Behind our house, some neighbors worked on clearing debris from a grate on the irrigation canal, to keep water from backing up into their homes upstream. Then a farmer who was a shareholder on the ditch showed up with the proper tools; he diverted the overflow into the spillway into Goose Creek. The engineered floodway was still performing admirably.
It’s hard to sort out what happened, when, over the next few days, because so much was going on all over the place. The rain and flooding continued on Friday. In Boulder, many homes started flooding due to rising groundwater, seepage, and backed-up sewer lines. The storms were intensifying to the west and north of us. A flash flood surged down the Big Thompson River, even bigger than the devastating flood of 1976. We couldn’t get any news about the Little Thompson, however. All roads and phone lines to the area were out, so we had no way to communicate with our neighbors at our property at River Way.
Meanwhile, Suzanne had come down to stay with us. With her house and family coping well with the rain, she had decided to go ahead with her planned trip to Hawaii with friends—assuming she could get to the airport. She may have been one of the last residents to make it out of her neighborhood, as the road was closed behind her due to severe erosion, and remained closed for a week. By Friday afternoon the weather to the south of us had eased up enough that highway 36 was opened for a few hours, and she was able to slip through to Mom and Joe’s house during that window. She caught her flight early Saturday morning without any trouble.
On Saturday, the weather cleared and the waters near us began to recede. The news focus shifted east now, as the flood crests moved downstream and started hitting towns that had experienced only moderate rain. Meanwhile, the helicopters took to the air, searching for close to 2000 people who were stranded in the hills with no other way out.
Our house remained high and dry, with power, phone service, and internet. If it weren’t for the sirens, emergency broadcasts, and helicopters, we could have been oblivious to the whole disaster. We counted our blessings again and again.
By Monday, the weather pattern re-established itself, and the rain resumed for a few more days. With the rivers high and the ground still saturated, a new wave of flood advisories went out, but when it was all over, not much additional damage was reported. In a week’s time, the city of Boulder received 20 inches, which is what we normally get in a year. In some places, 12 inches fell in 24 hours. One spot above Lyons received nearly 17 inches in one day.
At last, the rain moved on and beautiful weather arrived. The cleanup in Boulder was in full swing before the clouds were out of sight. It was amazing how fast the lesser damage was swept up and rinsed away. Most of the roads around town were patched up and reopened within days. Collection centers popped up all over town to receive the drenched contents of basements. Stores were overflowing with sump pumps, disinfectants, and other supplies for mopping up and rebuilding. It was impressive.
We ventured over to our storage unit to assess the damage, and were surprised to find that our locker was perfectly fine. A large section of the property had been badly flooded—the mud was literally hip-deep—but our area had been spared. Once again, we counted our blessings.
The helicopters were a constant presence for days. It was a heroic effort. In the end, everyone was accounted for and evacuated if needed. Many people chose to stay in their homes in the mountains, even though it may be months before roads and bridges are repaired, and “Winter is coming.” For many people here, self-reliance is a way of life.
Karel found plenty of air reconnaissance footage online. We flew, virtually speaking, along with the governor as he viewed the extensive flooding along the St. Vrain River. That’s how we got our first glimpse of Phyllis and John’s house. The house is still there, but has been pushed off its foundations. The river has completely changed course. It is now flowing through their front yard and around the north side of the house, right up against the garage. There’s also still a channel on the south side, so the house is on an island. We just learned that they won’t be able to rebuild, as their entire property is now in the flood plain.
At last, we got an email from our neighbor Jan, at River Way, calling for a meeting of the homeowners’ association to decide what to do about the “landscape alterations.” We were relieved to learn that everyone was fine and no houses at River Way were damaged. However, the river was dramatically changed and the flooding had caused a great deal of erosion.
On the day of the meeting, Jan had to meet us at the roadblock outside of Lyons to escort us through town. Lyons was one of the hardest hit towns. It’s closed for business for at least a few more weeks, maybe months, until power, water, and sewer can be restored, and the highways to the west are passable again. They’re not allowing the public in, so you need a security pass to drive through. The little downtown area didn’t look too bad, but a block away, we could see the devastation. Lyons will have a long, difficult time of recovery and rebuilding.
Northwest of town, Highway 36 is closed, but we were able to get to Blue Mountain Rd. via a small side road (Apple Valley Rd.). This 2-mile country road goes through one of the oldest settled areas of the Front Range. You can still see the remains of some of the apple orchards that were planted here about 140 years ago on the banks of the North St. Vrain River. It had never flooded like this in all those years.
Amazingly, the bridge at the west end of the road (the one that everyone calls “The Rainbow Bridge,” because of its shape) is still intact, although the highway is badly damaged at that point. We crossed the river and headed north on Blue Mountain Rd., into the Little Thompson river valley.
The Little Thompson (LTR) is a small river that frequently dries up altogether during drought years. One of the remarkable features of the LTR is that there is no highway running alongside it, as there is next to every other river on the Front Range. So, it tends to be off the radar. While the rivers to the north and south (Big Thompson and North St. Vrain, respectively) were making national headlines, there was hardly any news at all about the LTR.
The headwaters of the LTR are just below Rocky Mountain National Park, and the first major settlement along the river is a gated vacation community of 160 cabins and houses called Big Elk Meadows. They have (or, I should say, had) five constructed ponds, stocked with trout, held back by earthen dams. Only one of those dams, Meadow Lake, at 10 feet, was big enough to be monitored by the State. It was recently reinforced.
All five dams were completely breached. I don’t know exactly what happened when, because there have been no news reports except the failure of Meadow Lake Dam, which is the furthest downstream, on Thursday. Now, it seems to me there’s a flaw in the reasoning with regards to the State’s dam safety monitoring program. If a dam is less than 10 feet high, it’s considered too small to be a concern. In this case, there were four dams of less than 10 feet, all in a row, followed by a 10-footer. That’s about 40 to 49 feet of head, altogether, which is a serious amount of potential energy. The failure of the topmost dam sent tons of water crashing right into the next one, and so on, with no intervening miles of meanderings and floodplains to dissipate any of that impact.
So, there were one or two enormous surges of water that came crashing down the LTR toward the Blue Mountain area and our property at River Way, sometime late on Thursday or perhaps early on Friday. These surges carried along a bunch of huge ponderosa pines that had been living on the edges of those trout ponds. They made a nice logjam when they reached a narrow canyon, and a wall of water built up to a depth of over 30 feet, according to the owner of the land at that point. That dam burst sometime in the early hours of Friday, the 13th.
The reverse 911 calls had gone out to the residents of the Blue Mountain area shortly after the Meadow Lake dam breach was reported, late Thursday. Some homeowners just upstream of River Way watched the rising waters anxiously, and decided to evacuate to a neighbor’s house on higher ground, just in case. A few hours later, they went back to their place to get something they’d left behind, and just check on things. Their house was gone.
At River Way, Gail and Gregory had watched the swollen river getting closer and closer for two days. At first, with 200 feet of sloping meadow and some 10 or 12 feet of elevation between them and the river, they weren’t too concerned, but by late Thursday night it was clear that something had shifted, dramatically. They pulled their cars away and moved the short distance to Peter’s house to spend the night.
Jan, another River Way neighbor, told us that very early Friday morning the river suddenly started making a noise like a 747. It went on for a couple of hours.
When they ventured out at daylight, they discovered that the LTR had dug itself a new channel pointing straight at the big meadow at River Way. Rock-laden water was surging through it at high speed, hitting the meadow slope, and scouring it away like a gigantic, high-powered hydraulic jet. In other words, the river wasn’t just flooding over the land. It was quickly blasting it all away.
Nearly all the trees that lined the old river channel were gone. The old 1858 Buster homestead, across the river, was still standing, but nine of its outbuildings had been swept away.
The river had abandoned its usual course altogether. Not only that, but it had dug its new channel some 10 feet or more below the old riverbed.
By the time the water subsided, it had eaten through up to 20 vertical feet of alluvial soils. The meadow, which once sloped gently to the water’s edge, now ends abruptly at a sandy cliff with the river in a rocky bed at its foot. The two-acre buffer of land between the river and Gail and Greg’s house is completely gone; the edge of their driveway is right at the edge of the new cliff. They had to repair a portion of the road that leads to their house because it had fallen into the river. When Karel and I arrived for the meeting, they were working on repairs to all their utility infrastructure.
The next lot to the west, which is undeveloped, suffered a similar loss of real estate. The lot beyond that is the one that Karel and I own, where we someday plan to build our home. We lost approximately 100 feet of meadow and all the lovely trees that used to form our southern boundary line. The other two river frontage lots had comparable losses. Fortunately for us, our lot is still buildable.
After a brief tour of the new landscape, we convened our meeting and quickly came to agreement on various matters that had to be addressed. The biggest question, though, is what to do about the new features of our property. There are so many unknowns. Will the river return to its old course, or stay where it is, or do something else? What will be done upstream of us, and how will it affect us? For example, are the dams at Big Elk Meadows going to be rebuilt? Are other property owners going to push the river around to protect their property?
The way I look at it, a bunch of our topsoil is somewhere in Nebraska, and we now have a river going through our property, instead of marking the southern boundary. That’s fine, but we’ll have to take measures to protect the land from further erosion and figure out how to stabilize our new river banks. Otherwise, more and more of the meadow will erode away in every rainstorm, even if we don’t have another flood like this in a hundred years.
Which brings me back to that whole explanation about how this flood happened. The jet stream is powered by the temperature difference between the Arctic and the Equator. The Arctic has been warming faster than the rest of the planet, so the summertime temperature differential has been decreasing. The jet stream has been weaker and more erratic, and this stalling phenomenon, in which a storm just sits over one spot, sucking in moisture and dumping it for days, is becoming more common. It was a factor in the floods in Las Vegas, Calgary, and Europe, and Hurricane Sandy. They’re saying this was a 100-year, possibly a 500-year flood. The thing is, it could happen again next week.
People around here don’t find that so hard to believe anymore.
8 fatalities (The emergency warnings really worked! The death toll could easily have been in the hundreds.)
1500 to 1900 homes destroyed (estimates vary)
968 businesses damaged or destroyed
17,500 homes damaged
200 miles of road damaged
50 to 60 bridges destroyed (still unknown because some still inaccessible)
$2 billion total estimated property loss