By Dan Walton
The Windermere Creek rerouted from its original channel at the turn of the second millennium, leaving its new path vulnerable to the inevitable high waters that came a decade later. The rerouted section of the creek lies between Windermere Loop Road and the neighbouring old Scout camp, and its channel has been experiencing instabilities since a high runoff in 2011, then again in 2012. It has since continued to carry large amounts of sediment into Lake Windermere, and without immediate action, affected landowners are concerned the solution will only get more expensive and less attainable.
Likely due to human activity, the creek initially changed channel upstream of Windermere Bed and Breakfast Cabins around the year 2000. It continued to flow without any major disturbances until the high runoff in 2011.
And that really snowballed things, said Windermere Creek Bed & Breakfast Cabins owner Scott MacDonald. Because now instead of just water coming down with the heavy runoff, we have water mixed with gravel.
A study titled the Windermere Creek Hydrotechnical Assessment was prepared by Northwest Hydraulic Consultants, and presented to the Regional District of East Kootenays in January 2013. The regional district funded nearly one-third of the study, which looks at how the creek is eroding the channel. Land from the property of Windermere Creek Bed & Breakfast Cabins, in addition to upstream sediment and debris, is compiling in a delta at the mouth of the creek. The study notes that 5,300 cubic metres of sediment were deposited at the mouth of the creek in 2012 alone. It estimates that an additional 140,000 cubic metres of sediment will erode if no mitigation measures are applied, causing the delta created in Lake Windermere to become increasingly more shallow.
According to the assessment, high flows caused rapid channel degradation, transporting eroded material downstream; and upstream from the Windermere Creek Bed & Breakfast Cabins, a partial or complete blockage of overbank flow is likely to have caused greater turbulence, overwhelming the stabilizing tufa (flowing water will always carry sediments to its destination, but when it flows above an established bed of tufa a concrete-like rock formation which is resistant to erosion sediments are delivered at a modest rate).
Also reported in the assessment is that a change in the waters chemistry could be deteriorating the tufa.
Prolonged high flows of 2011 and 2012 likely resulted in decreased calcium or other ions concentration which may have impacted the resilience of the tufa layer, reads the report. It seems unlikely that high flows alone resulted in the observed changes.
Using a carbon-dated piece of wood found in the creek in 2011, the study was able to determine the river had been flowing through the same channel since at least 380 A.D. The runoffs of 2011 and 2012 were the highest in more than a decade, but comparable to runoffs over the past century.
For up to 300 metres, the creek flows through the channel it rerouted to in 2000, bypassing an established wetlands system before it reconnects again to its original channel, subsequently leading into Lake Windermere. But even after the creek rejoins with its original channel, the tumbling gravel from runoffs in 2011 and 2012 had beaten out the tufa layer that was holding everything in place, Mr. MacDonald said.
It dropped the creek bed level by about a metre because it took that tufa out, and with all the tumbling rocks that came down, it just chewed the heck out of the bottom of the creek.
Six mitigation options were offered in the report, and while the solutions are practical, they would all come with a hefty bill. Projects of this nature often have one-third of the costs covered by all three levels of government municipal, provincial, and federal.
The challenge in this case is that we do not have the means currently to raise our one-third with local taxation, said Regional District of East Kootenay Area F Director Wendy Booth. In order to do that, we would need to create a service area, which requires community support.
Creating a service area was recently achieved in Fairmont Hot Springs, which allows up to $50,000 in municipal taxation to support proactive flooding measures.