Through criticism and advocating towards a potential vision for long-term mitigations at Pigeon Creek, the public has weighed in and suggested ideas for upgrades on the mountain creek.
In a joint effort, the MD of Bighorn and Town of Canmore held a public information session on Aug. 6 at Canmore’s Civic Centre on long-term flood and debris mitigations on the multi-jurisdictional creek.
Flowing past Thunderstone Quarries and under the Trans-Canada Highway, Pigeon Creek cuts west through the hamlet of Dead Man’s Flats before reaching the Bow River.
The creek played a role in the 2013 flood’s effect on Dead Man’s Flats (DMF) and the quarry as debris such as trees, rocks and various materials from Thunderstone were swept into the culverts and hamlet.
To date, short-term mitigation measures have been made in DMF, including widening and raising the creek banks and introducing additional culverts, each having a capacity of 55 cubic metres per second capacity.
Bighorn Chief Administrative Officer Martin Buckley said completion of the long-term mitigations could be up to four years away, but concept designs may be presented in late fall or early winter.
The teaming municipalities are considering accommodating a 1 in 100 to 1 in 300-year flood event and just how much concentration it would produce, how much sediment/debris would be carried, controlling the water and how to strategize around it.
“Pigeon Creek is quite different, the risks are different, there is no risk of landslide and outbreak flood when dealing with sediment discharges,” said Andy Esarte, Canmore’s engineering manager.
Manfred Scheikl, from Alpinfra Consulting and Engineering in Austria, hired for mitigation designing, has completed some preliminary analysis of the area. He said they’re planning to avoid erosion on embankments and critical points during another event at the five sets of culverts and in the kink as the creek bends west in DMF and under the highway.
Alberta Transportation representative Paul Prout has indicated they will not upgrade the culverts under the Trans-Canada Highway.
Julia Eisl, Canmore’s flood mitigation mountain creek specialist, reiterated to her colleagues the importance of debris retention on Pigeon Creek.
“We have to do something with the debris,” Eisl said. “A basin, either a concrete structure or an embankment dam with an outlet structure and a rake in the middle to prevent wood to block it or go down and block the culverts. That’s the way we would like to go, having some debris retention and channel stabilization measures.”
DMF residents – as well as local business owners and developers – had their input before designs will be officially considered. Flood damages in total throughout the MD were estimated at just under $48 million, but residents argued the hamlet endured “minimum damage” during the flood and the mitigation problem can be alleviated before reaching the hamlet, opposed to further mitigation measures of the canal inside the hamlet that a “tank” can ride through.
DMF resident Paul Baumberg said what has been proposed at DMF is “out of scope,” at the meeting.
“I’d like to point out during the 2013 flood we had only maybe two-, three-, four-foot creek banks ... now we’re talking about some huge irrigation canal in case another event happens and quite honestly, it just doesn’t fit,” said Baumberg.
“I was under the impression everything with long-term mitigation involved everything upstream from the quarry so I’m not quite sure what this is supposed to be about.”
Along with residents lobbying for a more natural look, those in attendance said they would like to see mitigations downstream of Thunderstone before water and debris could reach the culverts and flow into the hamlet. Other suggestions brought forward included creating a sediment pond and flow splitting such as installing a culvert under George Biggy Sr. Road to direct flow east of the Trans-Canada Highway.
Tetra Tech EBA, a consulting engineering and sciences company, reiterated similar concerns about long-term mitigation proposed; such as the channel being too large, public safety and the level of protection being too high. The end results of an EBA meeting are not finalized as of yet.
“Regardless of hearing the outcome, we want to take another look at that channel and we think in discussion with folks at the MD and the community, there are things that can be done that address community concerns while still providing protection to keep the community safe,” Esarte said.
“I think we can find a way to make it work technically – it’s not an ideal situation – but I haven’t seen a single project yet where we’re dealing with ideal conditions. But I’ve seen solutions to those conditions on those projects. So I think we appropriately address the conditions we have and we do it in a way that minimizes the impact and maximizes the protection using the existing channel.”
River’s Bend Development partner Frank Kernick said mitigation measures needed to focus on the quarry and its supplies not being mobilized again. He suggested consideration of a diversion channel toward the west.
“There’s opportunity there for a 95 cubic metre per second flow to go through here and another area for it to re-basin with an overflow,” Kernick said. “Of course, if flows were that high, that would go across the highways … it would close the roads for a period time.”
In 2017, the MD will apply to the Alberta Community Resilience Program – a province-wide flood and drought mitigation grant program, in the mitigation efforts at Pigeon Creek.
