Boy standing on sandy island in a stream

A growing sediment island in the Dillon Creek wetlands, project update

As the second year comes to an end, Project Manager Miranda Cross described the growth of a sediment island within the new Dillon Creek wetland on Cortes Island and gave an overview of the restoration project. 

This project arose as a response to the algae blooms in Hague and Gunflint Lakes. Nutrients are entering the lakes from septic tanks, gardens, ditches, roads, creeks and livestock around the shore of the lakes.

After several years of monitoring the situation, a Friends of Cortes Island (FOCI) feasibility study suggested they restore the wetlands on Linnaea Farm to help limit the flow of nutrients from where Dillon Creek enters the lakes.

Cropped image of Miranda Cross

“It’s a three-year project. So in the first year we were doing planning and permitting, getting everything in place. In year two, which is just coming to an end at the end of March, we had construction and revegetation. And in year three, we’ll be continuing monitoring,” explained Cross. 

They will probably do some work in the upper Dillon Creek area this coming season, but have not yet decided what that will look like.

She reiterated the fact that Dillon Creek is one of many sources of nutrients entering the lake. 

“Take a canoe and circle around the edges of the lakeshore. Look at all the places that water comes into the lake. In pretty much every single inlet you see these growing deltas of sediment being deposited and that’s because pretty much every inlet has been modified by humans, whether it’s roads or farms or homes,” said Cross. “The exception to that would be little forest streams that are coming in from Kw’as Park, an area that hasn’t been ditched and drained.” 

One of the most intriguing developments in the new wetlands, at the mouth of Dillon Creek, is a growing sediment island. Cross estimates that it is composed of the equivalent of at least eight tandem sized dump truck loads of material from the creek. This was carried by fast channelized water travelling through the creek at high water.

“When it hits still water like the lake or a wetland, then all that sediment drops because it’s not moving anymore,” she said. 

Cross said this proves the wetlands is effectively filtering out nutrients that would otherwise have entered Gunflint Lake. 

Drone image of the sediment island being deposited where the fast moving water from Dillon Creek hits the slow moving water of the restored wetlands (Jan 15, 2022) – Photo courtesy Miranda Cross. 

“This is a huge success for the project.” 

But it also suggests that septic systems, runoff from farms and gardens etc are not the only source of nutrients entering the lakes.  

“Soil, I think, is one of the nutrient sources that is often overlooked and it’s a very large source of nutrients,” said Cross. “Soil particles carry nutrients, particularly silt, and when they’re deposited into the lake through biological and chemical processes, the nutrients get released and that’s what feeds the algae.”

Cross pointed out that the scope of FOCI’s first remedial project is limited to a pasture on Cortes Island’s oldest farm. 

They have no intention of, for example, trying to convert the entire farm into a wetland. 

“I recognize as a human being that I need food to eat. I really appreciate having local food. I used to garden more than I do these days because I’ve been so busy, restoring wetlands, but I like to support my local farmers and  I think that local food is very important in terms of a sustainable community,” she said. 

“What we’re really looking at is how can we maintain the productivity of the farm as well as restore habitat that will rehydrate the landscape and the forests.”

They need to limit the flow of sediments and nutrients towards the lakes. 

“There are many landscapes that are storing carbon currently, but are under threat because of these incised stream channels. They are lowering the elevation of the water in the forests, therefore making them more vulnerable to climate change as we’re experiencing droughts, heat domes, wildfires,” said Cross.

Hopefully there will be further remedial projects, at other nutrient entry points around the lakes. 

Meanwhile work continues at the Dillon Creek Wetlands Restoration Project. Last week, a load of rock was placed at the inlet and at the outlet of the creek, as a protection against erosion. The next step in the revegetation of the wetlands, which began last September, is a work bee this coming Saturday. 

The wetland’s ‘inlet’ prior to formation of the sediment island – Photo by Miranda Cross

Cross said much of the excessive flow of nutrients into the lakes began with human alterations to the landscape during the last 50 to 100 years. The sediments have been accumulating, but did not come to the public’s attention until the algae bloom of 2014. 

“Climate change could be a trigger,” said Cross. “Or it could just be that we’ve hit the breaking point where there’s just so much nutrient that’s accumulated over time. Like the soils, they settle out and settle to the bottom. So it is like a flushing of nutrients annually that is contributing to the algal blooms.”

In the last instalment of this three part series about the Dillon Creek wetland project, to be broadcast tomorrow, Miranda Cross talks about the revegetation project.

This post was originally published on Feb 6th and republished on Feb 19, 2022 as part of the Saturday Round-up.

Top image credit: Miranda Cross’ son Meco standing on the sediment island in the wetland – Photo courtesy Miranda Cross

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