Perseverance Creek: It’s More Than a Washed-Out Bridge

The creek found a new path

On January 30, a large rainstorm increased flows in Perseverance Creek. A log jam accumulated at the Hai Gai trail bridge, water backed up, overtopped the berm beside the creek and began flowing north across the low-lying land around the disc golf course.

There is a word for what happened: avulsion. Basically, a creek suddenly breaks away from part of its established channel and finds another route across its floodplain.

The new channel runs north from the bridge area toward the disc golf course and surrounding wetlands. The engineering report says the channel dried up again as seasonal creek flows declined in the spring, but it remains in place and is expected to carry water again once creek flows increase.

January’s weather was significant, but the engineers also found it was not unprecedented. Similar-scale rainfall and creek conditions occurred approximately two or three times over the previous decade. Whether another storm produces another avulsion depends on how the channel, sediment and woody debris continue to change.

There’s another interesting detail buried in the report: the original trail bridge at this same avulsion site washed out in November 2009 after debris built up against it.

So this isn’t simply a freak accident involving one unlucky bridge.

There’s a drinking-water well in the disc golf course

This was the part I hadn’t appreciated.

One of Cumberland’s groundwater wells is located right in the disc golf area.

The Coal Creek well was added to Cumberland’s water system in 2013. The Village says groundwater from the well normally supplies about 600 cubic metres of water per day, roughly one-third of normal system demand.

The January avulsion sent water through the disc golf area and flooded the road used to access the well. The flood assessment considers not only the well itself, but also its water-supply main, power and communications lines, and the road needed to reach it.

Interestingly, the report does not suggest that floodwater is simply pouring directly into Cumberland’s groundwater supply. The well sits on a raised pad, and its screened intake is more than 20 metres below ground beneath relatively low-permeability material. The assessment rates surface-water contamination of the well as a low hazard, although it notes uncertainty remains.

The access road is another matter. It flooded in January, and the report says there is nothing preventing that from happening again during future large storms.

That changes the question considerably.

It isn’t simply:

Where should we put a new trail bridge?

It is also:

How do we protect an important part of Cumberland’s drinking-water system when the creek itself may no longer want to stay where we put it?

Maybe the answer isn't putting the creek back

The flood assessment considered several ways of dealing with the new channel.

One option would more aggressively put Perseverance Creek back into its existing main channel. But that could require raising the existing berm, dredging, regular sediment removal and ongoing maintenance.

The engineers instead recommend further work on a setback berm near the well.

The idea is essentially to protect the drinking-water well and its access road while allowing the creek to migrate more naturally across part of the floodplain. The project could also be combined with restoration of wetlands and riparian areas.

The tradeoff is recreation. The report says the preferred option would likely affect trails and the disc golf course, and further planning would be needed to determine changes to the trail network and course layout.

There’s an interesting historical twist here too.

The engineering report estimates that around 1972-73, after the failure of No. 2 Dam, a berm was constructed at roughly the present-day avulsion site to direct Perseverance Creek west instead of allowing it to flow north into what was then the Rod and Gun Club area.

More than 50 years later, water overtopped the berm and once again found a way north.

Nature always seems to win eventually.

That doesn’t mean we do nothing. It means there may be a point where designing around the creek makes more sense than repeatedly trying to tell it exactly where to go.

A landscape with a lot of history

Coal Creek Historic Park contains the sites of Cumberland’s historic Chinatown and No. 1 Japanese Town. Chinatown developed alongside the mines beginning in the late 1800s and became one of the largest Chinese communities in Canada. The remaining Chinatown buildings were demolished in 1968, apart from Jumbo’s cabin, which was moved closer to Comox Lake Road.

After Chinatown disappeared, the Cumberland Rod and Gun Club leased some of the vacant land and operated its shooting range there. The Cumberland Museum says that after the destruction of Chinatown, the Rod and Gun Club leased some of the vacant land and moved its practice range onto the site.

The Rod and Gun Club lease ended in 2001. In 2002, Weldwood Canada donated a 104-acre property containing the Chinatown and No. 1 Japanese Town sites to the Village.

The modern 18-hole disc golf course opened in 2016, immediately south of the historic Chinatown site.

So in one relatively small area you have layers of Cumberland sitting on top of one another: Chinatown, the Rod and Gun Club, wetlands, trails, disc golf and municipal drinking-water infrastructure.

And running through all of it is Perseverance Creek.

That is what I missed when I first saw the washed-out Hai Gai trail bridge.

The bridge is the visible damage. The bigger issue is figuring out how Cumberland lives with a creek that has reminded us it has its own ideas about where it wants to go.