By Catherine A. Cardno, Ph.D.
Building on their experience designing for the London 2012 Summer Olympics, the whitewater design team for Rio 2016 has created a legacy park for the region.
The whitewater stadium for the Rio 2016 Summer Olympics will include a large central lake and two whitewater channels, one for use in Olympic competition, and one for use as a warm-up channel. After the Olympics, the facility will become a local whitewater rafting park. Prefeitura do Rio de Janeiro
June 9, 2015—In recent years some special-event organizers have been criticized for spending enormous amounts of money building venues that are only used once. But some are now reconfiguring their venues for new uses or designing them from the start so that they can be easily transformed into community amenities. A case in point is the whitewater stadium that is currently under construction in Rio de Janeiro for the 2016 Summer Olympic Games. Utilizing their experiences from designing the whitewater venue for the London 2012 summer games, the design team has created a venue that will challenge Olympians but that can also be used by the local community and visitors long after the games have ended.
The whitewater stadium will be located in the Deodoro Olympic Sports Complex. Within this Olympic cluster—which will host 11 Olympic sports and 4 Paralympic sports in 2016—the whitewater stadium will be built within a smaller park known as the "X-Park" that will also contain the Olympic BMX Center. The whitewater stadium has been designed by Glenwood Springs, Colorado-based specialty consultants Whitewater Parks International, in collaboration with the Newcastle upon Tyne, United Kingdom, office of Cundall, a worldwide multidisciplinary engineering consultancy.
Much like slalom skiing, the whitewater canoe and kayak athletes will be required to pass through a series of gates as they travel through the course. In the case of Olympic Canoe Slalom, however, the poles that form the gates are suspended from cabling above the water channel and athletes must pass through downstream gates with the flow of the water and upstream gates against the flow of the water—all without touching the gates with their bodies, paddles, or boats.
The stadium contains a large, still, central lake and two whitewater channels that run separately around opposite edges of the lake, feeding into it. A central building housing the pumps used to create the flow for the channels will be located at the edge of the lake and situated between the heads of both channels. Conveyor belts that run without water will move the boats from the lake to the top of the channels; when the channels are not in use, the conveyor belts will be stopped, the pumps will be turned off, and the channels will be dry.
The Rio 2016 Olympic competition channel will be slightly narrower than the London 2012 channel, above, but both feature an overhead cable system to hold the competition gates for the whitewater canoe and kayaking competitions. Whitewater Parks International
Both channels have been designed to the specifications of the International Canoe Federation, the international governing body for the sport of Canoe Slalom, but there is also an art to creating whitewater channels, according to Bob Campbell, the managing director of Whitewater Parks International. Whitewater rapids are often ranked according to an international scale of river difficulty. There are six classes that range from a baseline difficulty (class I) in which self-rescue should the canoe overturn would be considered easy to do, even without training, to the most difficult (class VI), which has extreme and dangerous rapids in which any rescue may not be possible. Olympic athletes compete on class III and IV rapids.
So one channel will be a class III to IV Olympic-standard competition channel that will be 280 m in length; it will have five pools along its length as it descends from the head of the channel to the lake, and its will include a 4.5 m drop from top to bottom with a water flow of a whopping 12 m
/s. "That's 12,000 liters every second," explains Damien Dungworth, CEng, a senior associate with Cundall.
"A small room might be 3 m by 2 m on plan, and 2 m high, so it's like the volume that would fill that small room, every second, continuously delivered down the channel," Dungworth says. "So they are huge volumes of flow that are put down the channel—it would fill an Olympic swimming pool in around three minutes."
The second channel will be a 200 m long class II to III warmup channel with three pools as it descends to the lake in a 1.8 m long drop. The water will flow more slowly in this channel, at a rate of 10.5 m
/s. "One of the goals in creating one of these courses is to try to manage the consistency of the hydraulic behavior so it's a fair competition," Campbell says.
In London, high-density polyethylene blocks were bolted together and connected to the bottom of the channel to form obstacles that constrict the flow of water, creating the whitewater features. The same design will be employed in Rio de Janeiro. Whitewater Parks International
"In nature, you might have a really exciting piece of whitewater, but it's 'surgey' and it's changing, and it's moving around," Campbell says. "If you were just paddling for fun, you might enjoy that unpredictable element of it, because you have to kind of read it on the fly and you're not really sure what's going to happen." What might be interesting recreationally can be problematic in elite athletic competitions, however. "In a competition you have to be concerned with consistency," Campbell says.
Designing whitewater channels "is not as simple as, 'Well, if you take this flow and this gradient, and this channel width and geometry, and put it all together you'll get this [result]," Campbell explains. Planning the channel and its obstacles "gives you the basis for having what you want," he says, but it is also helpful to build scale models to refine the design before the full-size version is built. (A 1:13 scale model of the Rio Olympic canoe slalom channel was created at the Czech Technical University Hydraulic Laboratory in Prague, and a YouTube videoshows the results.) Additional tweaks once the full-size design is built will still be necessary, as well.
In Rio, the bottom of the lake and the channels are formed from cast-in-place concrete bases atop waterproof geomembranes. The channel sides are created with precast concrete panels. "We didn't go for water-retaining concrete—we've gone for a lake liner with concrete placed on top as a cost-effective and robust way to retain the water, because leakage is a significant issue," Dungworth says. "Otherwise you're constantly losing water and constantly having to top up."
Within the channel, high-density polyethylene blocks will be bolted together and to the bottom of the channel to form obstacles that will constrict the flow of water in various ways, creating the whitewater features. The bottom of the whitewater channel incorporates steel channels that angle across the bottom, creating the visual impression that planks are laid along the bottom of the water channel. These steel channels enable the obstacles to be placed and angled anywhere desired when the pumps are turned off and the channel is dry. "Moving those obstacles is an important aspect of creating the whitewater and they can be refined at any time to get the flow to do exactly what you want it to do, to create good features in the whitewater," Dungworth says.
The central lake will hold 25,000 m
at a depth of roughly 1.8 m when the pumps are not running and the channels are not in use; the depth will be roughly 1.4 m when both of the channels are in use. "[The lake] only draws down about half a meter when you switch the channels on, but that's quite an important feature and that's why we have quite a big lake—so that it just draws down a manageable amount," Dungworth says. "Because that [amount] allows the channel to be operated independently and works for access to the water, for aesthetics, for all sorts of things like that."
The site comprises relatively well-compacted residual soils, according to Campbell. "We did however have some formidable drainage issues to contend with and eventually opted to incorporate [into the] layout a naturally sloping part of the site's topography," he noted. This siting, combined with a complex drainage system, ensures that during heavy rainfall water will not flow over land and into the lake, potentially contaminating the lake water.
Siting the stadium in this manner also "made practical use of the slope's natural amphitheater-like contour as a spectator-oriented design element," Campbell says. All of the seating and ancillary areas that will be necessary during the five days of competition during the Olympics will be temporary structures that can be easily dismantled, according to Dungworth.
After the games are over, the class III to IV channel will be used for whitewater rafting, while the class II to III channel will be used for training—both for whitewater sports and for swift-water rescue crews. An access port will be positioned so that cars could be moved into the channel and bolted to the steel channels that run along the bottom to make such swift-water training scenarios possible.
With only three years to design and build the stadium in Rio, the team decided to make use of the six years' of study and design that they had undertaken to create the dual channels and self-contained lake concept for the London 2012 games. "Our approach to designing these specialized facilities is ever-evolving," Campbell says. "In the case of the Rio project, we worked with our colleagues at Cundall to take a number of the most successful elements of our London Olympic design and improve upon them in terms of costs savings and energy efficiency."
"Particularly for post-Games legacy use, designing for financially sustainable operations is a critically important objective, beyond simply creating a successful Olympic sport venue," Campbell says.
The Rio Olympic channel uses 30 percent less energy than its counterpart in London because the channel fall was reduced from 5 m to 4.5 m and the flow reduced from 15 m
/s to 12 m
/s, according to Dungworth. Because the changes reduce the amount of water necessary to run the whitewater channels, the size of the pumps were also able to be reduced, which in turn reduced the cost of operating the venue.
The stadium is expected to be finished later this year.