Maybe We Should Explain What the White Water Feature Is and Why It's So Screwed
Notice that the Niagara River offers quite peaceful canoeing until you get to the ...
Dylan Kerelek from White Rock, Canada via Wikipedia
A self-referential anecdote here at the top. I never do this. Indulge me.
Several years back I’m starting out on a canoe trip in Canada with a bunch of guys. It’s the part I hate, carrying our canoes on our shoulders and our packs on our backs, stumbling down a trail to get around some rapids. I look out into the middle of the river, and there stranded up on some rocks is the bleached white skeleton of an old Grumman aluminum canoe. It’s been there a long while.
Old Grumman canoes were built like World War II airplane fuselages. You couldn’t tear one apart with a sledge hammer. This canoe has been ripped open all the way across its belly. It is hanging in two equal halves, one entire half pushed inside out like a banana peel.
The river did that. The force of the water tore that boat apart, probably in a few wild minutes. Trudging along, batting away flies, feeling every vertebra in my aging back, I am keeping my eyes on the bones of that boat. It focuses the mind.
So what does that have to do with anything in the here and now? A lot, I think. Earlier this week federal authorities sent city officials in Dallas a letter telling them to hurry up (again) on finding a solution to the mess the city created in the Trinity River five years ago when Dallas built an abortive concrete recreational feature called “The Standing Wave” or “White Water Feature” for kayakers. It occurred to me that in five years of ranting about it, I don’t think I’ve ever once really tried to explain what the white water feature is or what’s wrong with it exactly.
In the past I have described it as a fake rapids, which isn’t really accurate. The original name, the “Dallas Standing Wave,” gets closer.
In the part of the Trinity where the city built the wave, the river falls at a rate or gradient of about 1 foot per mile. For comparison, the Buffalo River in Northern Arkansas, a popular scenic canoeing river, falls at an average gradient of 38 feet per mile.
The Buffalo is walled by jagged cliffs several hundred feet high in places. Over the eons, big chunks of rock have broken off those cliffs and come bounding and banging down, kerploosh, into the center of the river.
When a fat, deep current of water falling at an average drop of 38 feet per mile runs into a boulder the size of a VW Beetle sitting on the river bottom, the water deflects in all directions including straight up, sending up a surge of water that may break the surface of the river as a “standing wave” — a wave that just stands there and never moves.
Standing waves are challenging and exciting for canoers and kayakers. If you hit a bunch of standing waves close together, a wave just behind you might lift up the rear end of your boat while another just ahead tries to push down on the front end. You have to maneuver fast, or the standing waves may fill your boat with water and capsize you. So, fun, excitement, the occasional unwelcome cold bath.
The Trinity, on the other hand, is a big, slow, muddy river with a very gradual fall. It can be deceptively powerful and, in fact, every year or so takes the life of some unlucky boater who underestimated its sheer plodding power. But nature just didn’t give the Trinity much in the way of excitement. Floating down the Trinity most of the time is a serene, contemplative and relatively uneventful experience.
The Dallas wave was an attempt to create something exciting in the river — a worthwhile goal for a number of reasons. The river in Dallas today is not rated by the state as safe for contact recreation because of high E-coli counts, but if enough people were out there braving it anyway the state would be obligated to impose higher water quality standards. Strange as it may sound, people playing in kayaks and canoes could be the brave pioneers who force North Texas to clean up the river.
Yes. The Standing Wave could contribute to making the Trinity River a beautiful and treasured recreational resource. If it worked. But it doesn’t.
The city built two concrete dams just downriver from downtown near Corinth Street and South Riverfront Boulevard. Technically they are weirs, because water flows over them. They extend three-fourths of the way across the river at a height of about 5 feet from the bottom of the river, the idea being that during most of the year the water in the river would go over the first weir, crash down the other side, hit the pool of water created by the second weir below, sending up standing waves at the bottom of the first weir sort of like what I described on the Buffalo.
It does work for the kayakers. Using what are called “play boats” — little snubby kayaks that can turn on a dime and are easy to propel —they can zip down, across and back up into the standing wave, play off the roll and use the turbulence to propel their boats back and forth across the bottom of the higher weir. It’s pretty cool to watch.
So what’s wrong? According to federal law from pretty much the beginning of the nation, you can’t put something in an American river that “impedes navigation.” Obviously nobody was navigating up and down the Trinity in a cruise ship before the wave was built, but fishermen were able to go upstream in small, flat-prowed aluminum “jon” boats with 10-horse power motors.
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The city promised the Corps that the wave would not change any of that. The city proposed to build two “bypass channels,” one next to each weir, separated from the main channel by a wall. Canoes and jon boats could use the walled bypass channels to get up and down the river.
But, problem. The entire wave — both sides, standing wave and bypass channel — creates a gradient or drop of 5 to 6 feet in a distance of 115 linear feet of river. If the river falls that much in 115 feet, the bypass channels have to fall that much. That’s a swift drop. If you ran the entire bypass channel down at that angle or drop, the water in it would be roaring down it at a high rate of speed and so would you. And getting back up it in the other direction, even with a 10-horse power motor, would be extremely challenging.
The Standing Wave or White Water Feature was not a terrible idea. It just didn't work.
According to the correspondence between the city and Corps of Engineers that I have read over the last two weeks, engineers at the Corps have determined that the bypass channels don’t fall at the same rate as the water going over the weirs. The bypass fall is much gentler, taking a boat down only two of the total six feet of drop that must be descended over the full length of the wave. So what about the other 4 feet?
Oh, that. At the bottom of the second chute is a sheer 4-foot drop. Straight off the end. That sheer plunge of water causes a steep standing wave just ahead of where it lands. In the language of the engineers, the channel comes to “an abrupt drop of approximately four feet followed by a rise of approximately two feet.”
A canoe or kayak doesn’t float out into the air off the end of a chute like a Wile E. Coyote cartoon and then land flat on its belly in a “coyote fall.” It tips down off the edge nose-first and dives straight in. Teresa Patterson, an experienced kayaker in 2011 and now a kayak instructor, took a kayak down the bypass chute in May of 2011, four days after the official unveiling of the SWWF. She described being slammed back and forth against the walls of the channel, then going off the end and being driven deep into the river by the force of the water, then being pulled underwater again by the turbulence.
“I thought, well, I'll just swim out of it. Normally if you're in turbulence and you get dumped, you can just swim out. But it teased me. It looked like it was going to work, and all of a sudden something grabbed my ankles and I was underwater again.”
Five times. It took her ten minutes of struggle to get out of the turbulence. Needless to say, no one in a jon boat can make it upriver past the wave, except in a cartoon.
Patterson’s experience and the equally harrowing experiences of others caused the city to try to legally disavow the wave without fixing it. The city said it didn’t exactly endorse using the wave, but they didn’t really tell people they couldn’t use it, which, if nothing else, has been a new high-water mark in sheer civic fecklessness.
But why does it work like that? Why would the city have built a more gradual drop all the way to the end of the chute — creating an impression of safe-going — only to dump people off a waterfall at the end and into a turbulence some have called “The Cuisinart?” I believe the online expression is WTF?
I have pored over the back-and-forth between the city and the Corps. In those emails and letters I have found at least a couple of places where the Corps has called the city’s attention to what it politely calls “computational error” — problems the Corps found in the mathematical engineering models the city had presented. More pointedly, the “computational errors” all seem to be contradictions between models that show the 4-foot drop and others that don’t.
I don’t know that anybody was faking anything here. Another explanation might be that the city engineers who oversaw the construction were not competent. A third might be somewhere between the two extremes. Maybe they couldn’t get the calculations to come out right. Hydraulics was not their thing. Anyway it was just a bunch of goofy canoes going down a river. Maybe the 4-foot drop — a kind of computational glitch they couldn’t erase from their computer screens — didn’t seem all that important.
The city is threatening now to sue contractors, of course. In the correspondence, the main engineering contractor says the city didn’t build the wave the way they designed it. All of that either does or does not go to court some day.
But, look. It’s our city. It’s our river. Our city told us they were building something in our river that we could use safely. It was our city’s job to check the designs and get it right before they built it.
So this is where I circle back to the bleached bones of that old Grumman canoe. The weight and force of moving water is not something that people understand intuitively. I think you have to experience it. You have to see it with your own two eyes.
The wave was built by people who just didn’t know what they were doing, didn’t know what they were dealing with, didn’t understand the consequences of getting it wrong.
As originally proposed the wave was to cost $1.5 million. At completion it cost $4 million. Last week I asked a compliance officer for the Corps what it might take to fix the bypass channel. He said he didn’t know but it could be a new channel two to three times the entire length of the existing wave. I will leave it to your imagination how many more millions that might cost.
Hope this helps.
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