Instream improvements

Instream improvements

Healthy salmon streams are characterized by “channel complexities” such as fallen logs, overhanging vegetation, boulders and smaller gravels, riffles and pools.  These all work together to provide places where salmon can rest and hide, where juveniles can feed and where adults can spawn.

Heavy stormwater flows in urban streams such as Cougar Creek tend to destroy these features and/or bury them under a load of sediment.  Lower Cougar Creek in particular is subject to lots of sedimentation, because as the velocity of flow decreases in this shallow stretch, sediments drop out.

Since 2016, Streamkeepers have been using the “fishery window” (August & September) to install shallow rock dams called weirs in Cougar Creek’s most productive spawning areas near Westview Bend.  In addition to creating some deeper, cooler pools in which salmon can take refuge, weirs also cause water to tumble, which in turn increases its oxygen content.

Weir construction, Lower Cougar Creek, 2017 August 21
Weirs after first heavy rains, 2017 October 27

Surrey’s SHaRP (Salmon Rehabilitation Program) teams have also installed weirs in the stretch of creek between Scott and Nicholson Roads.

During the fall 2019 fishery window, the City of Delta’s “crib box” project at Westview Bend provided further channel complexities, much utilized by spawners and fry ever since.

Crib boxes (here, newly planted October 2019) provide shade, hiding & resting places for fish

But not to forget those beavers! Their tree-cutting and dam-building habits are a nuisance, and yet their ponds provide excellent habitat not only for salmon fry seeking cool deep water, but also for a wide range of other creatures. In fall 2020, we undertook a “beaver pond leveller” pilot project on Lower Cougar Creek — in collaboration with Burns Bog Conservation Society, City of Delta, EBB Consulting and Pacific Salmon Foundation — to see if we can maximize beaver benefits while reducing trail flooding and ensuring upstream access for spawners.