The riparian zone is the vegetated buffer along the banks of a trout stream. This diverse area of growth is vital to the health of all flowing streams. The root systems from the plants keep the banks stable and prevent erosion during high flow events. The cover of willows, trees, sedges and grasses that grow in this environment provide shade and cover for trout both on the banks CLICK THE FISH and down into the water!
Mature deciduous trees such as poplar are especially important along a trout stream riparian zone. The root systems from these trees are large and they will migrate along the streambanks, where they become a strong re-enforcement meshing root system.
Willows are fast growing and they compliment larger tree growth and add to the needed bio-diversity that makes our trout streams special environments for not only trout, but the other wildlife that populates these vegetated areas. I always enjoy watching this wildlife while fishing my favorite spots!
How Do Root Systems Benefit Stream Banks?
To understand the importance of willow and tree root systems better, think of how and why rebar or wire mesh is added to concrete to make it stronger. Straw is added to mud to build houses in some countries for the same result!
The following photo shows a bank erosion site on a small trout stream. On the left side of the photo, you can see how the stream bank is undercut, yet the root systems are holding the soil together. In the center of the photo, there is a small break in the trees and willows where there is limited root development and the bank is crumbling down into the stream channel. On the right side of the photo, you can see how the stream bank relaxes down to the water’s edge, held together by the root systems of willows and trees.
Once the undercut bank relaxes and creates a health slope with both grasses, willow and tree plants still intact, the streambank stabilizes. This stable part of the stream bank will withstand future erosion events better than the center section and reduce silt loading into the stream channel.
Grasses and sedges play an important role in the riparian zone. In areas that have been flooded by beaver dams, the first recruitment plants for the riparian zone are grass and sedge. Although the root systems of these plants are smaller in size, compared to willows and trees, they do a great job at helping to stabilize the stream banks.
The photo above; shows how canary grass provides good bank cover for any resident fish in this stream. At the end of the growing season, the weight of snow will collapse the long canary grass down over the stream channel, where it provides excellent overhead cover for the stream’s fish. Western Water Sedge is also quite common along the stream banks. It’s root systems are very tough and they can withstand a substantial high flow event. These partially submerged grasses and sedge also provide great habitat for aquatic invertebrates as well!