Skip to contents
Outdoors

How technology is turning the South Platte River into a wavy, whitewater hot spot

Two hydraulic WaveShapers at Sheridan’s River Run Park have boosted Colorado river surfing big time, despite the challenge of down-to-the-drop demands on Colorado's water.

Ocky Koa gets in some early morning surfing at the River Run Park, a pair of river surfing waves on the South Platte near the Broken Tee Golf Course in Sheridan. (John Leyba, Special to The Colorado Sun)
  • Credibility:

SHERIDAN — The dawn hasn’t yet dimmed the early morning headlights when Ocky Koa, a data analyst in his mid-40s, hops out of his pickup and strolls just past the bike path at River Run Park, where the day’s first recreational cyclists and commuters zip by along Sheridan’s stretch of the South Platte River.

There, beneath metal doors flush to the side of the hill, sits the hydraulic control center for a contraption that helps carve a portion of the South Platte’s surging flow — 1,100 cubic feet per second on this morning — into a perpetual wave. 

Later, enticed by hot weather and optimal conditions, dozens will gather on the banks of River Run Park to take turns surfing the feature that locals have nicknamed Benihanas, partly in honor of the boarding move of the same name and partly as a nod to Ben Nielsen, the designer who installed the mechanical WaveShaper.

It takes just $5 a month to make more journalism like this possible. Step up and become a Colorado Sun member today.

The urban South Platte River now has two of these adjustable systems — the other, newer one sits about a half-mile upstream from Benihanas — that are relatively rare in the U.S. Similar systems are installed in Bend, Oregon, and Boise, Idaho.

Ocky Koa has been trained to adjust the three steel flaps embedded in the river bottom for maximum fun and safety — a responsibility entrusted to only six volunteers. He takes special care to keep his legal name separate from his surf persona, under which he also provides river flow and condition reports online. Most of the whitewater recreation community knows him simply as Ocky, a dedicated triathlete and lifelong surfer on both the East Coast and occasionally in Hawaii before he moved to landlocked Colorado. 

The river has brought him back to a sport he loves.

“As a shaper, I’m privileged and humbled to be asked to be part of that crew,” he says. “What makes this unique for us is the fact that we have this wave feature we can manipulate to be the best quality and safest feature we have in the state. If I shape a wave and can look down and see 40 guys and gals with smiles, hootin’ and hollerin’, where can you facilitate that level of fun? It’s a cool thing.”

The importance adjustability in whitewater features has been highlighted this season as both Avon and Basalt struggle with recently renovated man-made waves flipping rafts and sending paddlers on long, sketchy swims.

Ocky unlocks the twin metal covers that open to reveal the hydraulic controls for the flaps installed perhaps 30 yards away, in the center of the South Platte. He lowers himself into “the pit,” as he calls the underground control center, and scans the latest page in a black binder where the wave shapers record the river’s flow, the flaps’ settings and other observations.

He notes that the flaps haven’t been moved at all in the past five days.

“We’ve been consistently high for the past two weeks,” he says, noting flows that have ranged from 800 to 1,200 cfs. “Which is phenomenal. We have not had that in years past.”

A red digital readout illuminates three numbers that indicate the precise angles of the underwater flaps. The two outer flaps show positive numbers, which means they’re tilted upward, while the middle flap shows a negative reading, or a downward angle. The result is a flow that pours down the river’s natural drop before curling up into a surfable crest.

In times of lower flows, Ocky or one of the other volunteers will work the three black knobs that move the flaps to create a wave that optimizes the riders’ enjoyment with an eye toward keeping the experience safe for everyone — surfers, kayakers, tubers — tapping into the flow. A slight adjustment in this direction on one knob, that direction on another, results a minute or so later in an altered path once the flaps have redirected the river’s energy.

“There’s a bit of physics in it,” he says. “A little physics and a lot of what I call artwork.” 

Ocky Koa updates the settings in a log book as he stands in the underground control center before he gets his early morning surfing in onJuly 9, 2019. The wave-shaper flaps controlled by the center work to create surfable current, but the South Platte has been running so fast that it hasn’t been necessary to adjust it. (John Leyba, Special to The Colorado Sun)

The wave features, six of them in about a three-quarter mile stretch south of downtown, have been eight years in the making — one part of many projects undertaken by a variety of nonprofits and governmental jurisdictions along the channel’s urban corridor. 

They were designed to address everything from flood control to ecology to fisheries to whitewater recreation, and taken together they have in many ways redefined a river once written off as little more than a cesspool. Since recreation loomed as one key element of the wish list, Ben Nielson, a New York-based river designer for Merrick & Co., got pulled into the planning along with its Denver-based division, McLaughlin Whitewater Design Group, which built one of the nation’s first whitewater parks in the late 1970s, the Confluence Park in downtown Denver. Rick McLaughlin and Gary Lacy, who was a senior in high school when he worked on Confluence Park with McLaughlin, seeded an entire whitewater park industry and established Colorado as an international hub in park design. 

McLaughlin, Lacy’s Boulder-based Recreation Engineering and Planning, Scott Shipley’s S2o Design in Lyons, River Restoration in Carbondale and Whitewater Parks International in Glenwood Springs all have built parks around the world, including Olympic whitewater courses. 

“River surfing is a fast-growing activity,” Nielsen says. “When that (first feature) got built, it was crazy successful. The river surfing community, which has had so much growth on the Front Range because of River Run, exploded.”

MORE: Controversy over Denver Water’s Gross Reservoir expansion offers a glimpse into water woes in the West

In the space of two years, he says, one of the community’s Facebook pages grew from a few hundred members to more than 1,000. When the river flow was adequate, you might find 30 surfers waiting in line to take their turn on that single WaveShaper at the park just west of the Broken Tee Golf Course. 

So the question beckoned: Should a second one be built?

It made sense, though the decision wasn’t entirely driven by recreation. Two natural drops in the river, just upstream from River Run Park, had failed and become a barrier to the movement of fish and other aquatic life, Nielsen recalls. 

Based on the fact that development had already crept to the river’s edge, there was no way to restore the river to its original condition. But within the constraints of an urban environment, the grade and flood protection could still be controlled.

“Recreation is an add-on to that,” Nielsen says. “It’s one of those projects where they look at river system holistically. And it’s really interesting in an urban setting, because there’s a lot of pressures on the river. It’s a great puzzle to try to solve.”

Workers installed the second WaveShaper last fall and winter, after a miserably dry 2018 summer. But in retrospect, that wasn’t all bad. Construction took advantage of the low flow.

Like the first one, the second WaveShaper also operates its hydraulics on biodegradable vegetable oil. The new one added another twist — it’s solar powered. It officially opened on June 5, but it has been undergoing adjustment and as Ocky says, “remains a work in progress.”

Ocky Koa waits for a wave on July 9, 2019. The river park’s upper wave (Benihanas) is a high-speed, dynamic wave while the lower wave section (Chiclets) is designed for beginners. (John Leyba, Special to The Colorado Sun)

Whitewater parks in some parts of Colorado feature sufficient flows that don’t require adjustable flaps to optimize their recreational use. But in the urban South Platte, so many factors play into the release of water from Chatfield Reservoir that surfers and kayakers inevitably need a little help.

Take, for instance, the odd circumstances on the river last week.

Just a couple days after the South Platte was running over 1,000 cfs, state river operations workers planned an 1,800 cfs release from Chatfield for four hours last Thursday morning to assist with a sediment load sampling project near the South Platte’s confluence with Cherry Creek. 

After the release, the reservoir gate was to be adjusted down to 500 cfs — but was accidentally taken to zero, where it remained for three hours. The error was corrected, but the shut-off resulted in a period of extremely low flow.

Ocky, on an email list for both the Colorado Division of Water Resources and the Army Corps of Engineers, had been advised of the plan to release water from Chatfield. Calculating about a four-hour lag from when the gates are opened or closed at the dam and the resulting flow arrives at River Run Park near West Oxford Avenue, he arranged to show up in time to reshape the wave at Benihanas. He didn’t know about the mistaken shutoff until he arrived. Then he received a second notice that the flow was being restored.

MORE: Even after a rush of snow and rain, the thirsty Colorado River Basin is “not out of the woods yet”

At that time, the flow at Benihanas was only about 160 to 170 cfs. “I tried to clean it up as best I could,” Ocky says, “and then I realized it was a lost cause.” So he headed upstream to the newer WaveShaper to see if he might make the feature surfable. He was trying that while on the phone with Nielsen when the restored flow started taking the water level higher, until surfing would no longer be safe — but Ocky adjusted the WaveShaper to make it safe for kayakers and tubers and other recreational users.

Then he headed back to Benihanas to reshape that wave with the help of the increased flow — no easy task because the river continued to rise. 

“We adjusted it the best we can, knowing water’s still coming, but allowing for about 17 people in line to catch waves,” Ocky says. The next morning he returned “to clean up the wave and tune it up.” 

Then came a notice that a release would increase the flow from 500 to 600 cfs by noon. Ocky and another wave shaper named Dan, who both have day jobs, took a guess at the best setting to take surfers through the day. Dan returned after work to fine tune it.

In a summer of generally higher flows, the glitch put the WaveShaper to the test and showed why it’s so valuable on a river of such variable volume.

“It allows for a really good wave at a multitude of ranges,” says Dan, who also shies away from using his full name. “When it gets down to 180 to 300 or 400, that’s when the adjusting mechanism really comes into play.”

As much as the mechanism, the skill of the human wave shaper figures into the equation. There’s an intuition involved that comes only from experience.

“I’ve been river surfing and kayaking for the last 20 years,” Ocky says. “All sorts of factors go into consideration. I can make my guesses and predictions. But just when you think you understand, they change it again. I can’t pretend to understand all the science.” 

From a windowless office in Greeley, Brent Schantz studies spreadsheets reflecting water rights dating to the 19th century to determine how the flow of the South Platte River needs adjusting from Chatfield Reservoir to the Nebraska state line. Since 2011, Schantz has been South Platte River Operations and Compact Coordinator for the Colorado Division of Water Resources. (Kevin Simpson, The Colorado Sun)

Brent Schantz understands the science — and a lot more — about water in Colorado. In a windowless office on the second floor of a downtown Greeley building, he supervises the flow of the South Platte River from Chatfield Reservoir to the Nebraska border for the Colorado Division of Water Resources.

Like Ocky Koa, his skills can be broken down into some combination of science and art, calculation and intuition — though for Schantz the calculation necessarily dominates. Since 2011, he has held the title of South Platte River Operations and Compact Coordinator, which means each day he must balance the demands on the river, defined by water rights dating back to the 1860s, with the in-flow from tributaries, runoff and rainwater.

Once the calculation is complete, he determines whether the Army Corps of Engineers should pull the lever to release or hold water from Chatfield, or simply maintain the “native flow.” 

In some ways, it’s basic math, though the variables involved come from myriad sources. The calculus takes into account inflow minus diversions. Water rights must be prioritized. Weather forecasts must be heeded in the event precipitation adds to the flow.

Then Schantz computes a rolling three-day average, which reduces the chance that a sudden spike will prompt too much of a release, or too little. “Otherwise,” he says, “you’re up and down every day.”

Schantz’s decision on the day’s flow eventually finds its way, through the Corps of Engineers, to Ocky and the wave shapers. If there’s a release that could render their wave mechanism useful, then they make their own calculations. 

But one simple fact remains: Popular as river surfing has become, it doesn’t register a blip on Schantz’s computer screens. His attention remains on the people and entities whose water rights nurture livelihoods and serve public utilities.

He checks three different weather websites and radar maps. If he sees the area above Chatfield is likely to get hit with a lot of precipitation, he knows the next morning that he won’t need to release any extra flow. He plugs in numbers from Denver, Centennial and Englewood and factors in that the flow shrinks a half-a-percent per mile and makes his call.

“You learn to have patience and not just react,” he says. “But at the bottom end of a runoff — usually the first part of July things start dropping off — you have to stay ahead of that so you don’t create a big hole in Chatfield that you have no way to fill back in.”

This is where the art comes in. 

“It’s just experience and knowing what the demand is downstream, knowing what the irrigation demand is,” he says. 

MORE: Colorado Springs’ downtown creek has long been viewed as a blight. Then one man started catching trout in it.

From what he can tell, Schantz figures that river surfers could end up getting all the water they can handle this summer.

“It may be flows are too high, too dangerous for them to get out there at the peak,” he says. “But times leading up to and coming off that — that may be their perfect storm. They’re going to have a great time and talk about water year 2019, when the wave machine was the best they’d experienced.” 

Ocky Koa heads down for his early morning surfing session on the South Platte on July 9, 2019. (John Leyba, Special to The Colorado Sun)

Back at what he calls “the dawn patrol,” Ocky Koa peeks out from the pit to see how his adjustments have shaped the river. The wave narrows, then widens out to a more surfable configuration. Ideally, Benihanas flows “wide and green.” If there’s another surfer nearby, Ocky might ask them to test the wave and offer a quick critique.

But this early, he’s the only one with plans to take a few rides before heading to his day job.

And besides, this summer the mechanism hasn’t needed much adjusting. Last summer, when drought and subpar snowpack left flows running at a comparative trickle, the shapers had their work cut out for them to coax the flow into a surfable wave.

This year has been different. The stretch of the South Platte that churns beneath the Oxford Avenue overpass has consistently flowed higher than normal since the heavy mountain snowpack began its slow but massive melt. Nature hasn’t needed a lot of fine-tuning.

“We were at 170 (cfs) two years ago,” he says. “We’re 10 times that right now.”

Is it possible to have too much of a good thing? Not within the parameters he’s seen here — even for surfers who are just learning. 

“The benefit this year of having as much water as we have is that a lot of people have made a lot of progress and really improved their overall surfing skill because they’ve had consistent water,” he says. “So much of river surfing has to do with muscle memory and consistency. Having this much water has afforded people the opportunity to get out four, five or six days a week.”

The simple truth in this year of incredible snowpack, and runoff that already has extended the season well beyond years past, is that there’s not much to adjust beyond very minor tweaks. On occasion, the volunteer wave shapers might get a message from surfers asking that the feature be adjusted in a particular way, but even those requests have disappeared this season.

“If you come out here tonight around sunset, between 4:30 and 8 tonight, there’ll easily be 30 people hanging out,” Ocky says. “On a weeknight, everybody gets off work 4:30 or 5 o’clock and the line will be 20-30 deep. When we first started, there were eight people.”

So Ocky changes into his wetsuit, slips on his life vest and helmet, picks a board from his truck and wades into the river. He sinks chest deep in the water before rising onto one of the large rocks that frame the wave feature. The sun has risen high enough to bathe him in golden light.

“I love getting the morning sun, I love getting the workout in,” he says. “I can spend the rest of the day living on the excitement of the morning.”

He crouches, clutching his board in both hands, calculating the best spot to carve into the churning water. He leaps forward and catches the wave perfectly, beginning a two-minute slice of heaven that ends only because he has decided to end it, make his way to the shore and begin again.

Ocky Koa. (John Leyba, Special to The Colorado Sun)

The Colorado Sun has no paywall, meaning readers do not have to pay to access stories. We believe vital information needs to be seen by the people impacted, whether it’s a public health crisis, investigative reporting or keeping lawmakers accountable.

This reporting depends on support from readers like you. For just $5/month, you can invest in an informed community.