Growing sedimentation in the new Dillon Creek wetland and an update

Roy L Hales/ Cortes Currents - 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 concluded that they restore the wetlands on Linnaea Farm to help remove nutrients from waters entering the lakes from Dillon Creek.

“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,” said 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,” explained 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.

“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.”