By Enrique Massot
The County News
Controlling the flow of three rivers at once could allow much better flood mitigation than the Springbank dam and off-stream reservoir, a civil engineer says.
“There are four rivers causing flood,” said Dr. Emile Gabriel. “If we work on one river only we are missing the other three.”
Gabriel, president and CEO of Trinity M.C.G. consultancy, began studying flood mitigation alternatives after the catastrophic June 2013 floods in the Calgary region.
Speaking at a Nov. 10 presentation in Redwood Meadows, he said the Tri-River Joint Reservoir option would allow controlling three flood-causing rivers with a single dam and reservoir
Gabriel was dismayed when the NDP Alberta government backtracked from an election campaign promise of building a dam at McLean Creek and instead decided to keep the previous government’s choice to build a dam and reservoir in Springbank.
“I asked, why so close to the city?” he said.
Gabriel said earth dams are subject to breaks, citing the 2014 break of the Mount Polley dam in B.C.
“This happened just three years ago,” he added.
In case of failure, the 15 km between Calgary and the Springbank dam would leave little time to prepare, as water would take just 15 minutes to reach the city.
The Springbank project was designed to protect Calgary from a 2013-sized flood.
However, Gabriel said, “no expert can guarantee the next flood will be equivalent to that of 2013.”
And as roadblocks to the Springbank project multiply, Gabriel said the government should give a chance to the Tri-River Joint Reservoir option.
Dr. Karen Massey, a Redwood Meadows resident, was concerned the Springbank dam would leave the townsite without upstream protection.
“History has shown from the 1995, 2005, and 2013 floods that the rip rap on the berms get washed away,” she said. “We don’t want our basements flooded in Redwood Meadows when…water from the proposed Springbank reservoir creates pressure on the springs and start to back up.”
Controlling the Elbow, the Sheep and the Highwood Rivers would reduce flooding in most of the Calgary area. Because the three rivers are tributaries of the Bow River, controlling their flow could also help control the Bow downstream of Calgary.
Taking advantage of the topography, Gabriel’s plan would allow for diversion of water from the Elbow and the Highwood Rivers to a reservoir formed by a dam on the Sheep River running between the two.
The resulting reservoir would be 30 km long and one km wide, able to contain 10 times the 70 million cubic metres for which the Springbank dam is designed.
Gabriel said the Springbank dam would be sitting on clay, whereas a concrete dam at Tri-River would be built on a solid rock foundation.
The Springbank dam has been designed to store flood water only temporarily.
“But you can’t store water or generate power with it,” Gabriel said.
Instead, the permanent water storage provided by the Tri-River project could be used to generate power, to supply water to Okotoks, for irrigation and for forest firefighting purposes.
“The Three-River project is an investment,” said Gabriel. “Springbank is not an investment at all—it’s a liability.”
Gabriel said some objections focused on the fact the Tri-River project would be in Kananaskis Country.
However, he said, “you have engineered structures such as Lake Minnewanka, where a dam was built to generate hydroelectric power.”
The Spray Lakes Reservoir, built in 1950, is another example of engineered structures in Kananaskis Country.
Gabriel, who built the Tri-River concept on a voluntary basis, could not provide an estimate cost for the proposal, which should be part of a provincial study. However, such study will need to take into account that the Springbank project would have an annual maintenance cost and yield no benefits, while the Tri-River project could generate annual benefits in irrigation, water supply and power generation.