The Value of Riparian Vegetation
 Stream
or river banks are riparian areas, and the plants that grow there
are called riparian vegetation. Riparian vegetation is extremely
important because of the many functions it serves.
- Bank stabilization and water quality protection
The roots of riparian trees and shrubs help hold streambanks
in place, preventing erosion. Riparian vegetation also traps sediment
and pollutants, helping keep the water clean.
Fish habitat
As dying or uprooted trees fall into the stream, their trunks, root
wads, and branches slow the flow of water. Large snags create fish
habitat by forming pools and riffles in the stream. Riffles are
shallow gravelly sections of the stream where water runs faster.
Many of the aquatic insects that salmon eat live in riffles. Salmon
also require riffles for spawning. They use pools for resting, rearing
and refuge from summer drought and winter cold.
Wildlife habitat
Over 80 percent of all wildlife species in western Washington
use riparian areas during some part of their life cycle. Riparian
vegetation provides food, nesting, and hiding places for these animals.
Unfortunately, forested riparian areas account for the smallest
percentage of forest land in Washington.
Food chain support
Salmon and trout, during the freshwater stage of their
life cycle, eat mainly aquatic insects. Aquatic insects spend most
of their life in water. They feed on leaves and woody material such
as logs, stumps and branches that fall into the water from streambanks.
Standing riparian vegetation is habitat for other insects that sometimes
drop into the water, providing another food source for fish.
Thermal cover
Riparian vegetation shields streams and rivers from summer
and winter temperature extremes that may be very stressful, or even
fatal, to fish and other aquatic life. The cover of leaves and branches
brings welcome shade, ensuring that the stream temperature remains
cool in the summer and moderate in the winter. Cooler, shaded streams
have less algae and are able to hold more dissolved oxygen, which
fish need to breathe.
Flood control
During high stream flows, riparian vegetation slows and
dissipates floodwaters. This prevents erosion that damages fish
spawning areas and aquatic insect habitats.
Riparian vegetation is essential for maintaining high water quality
in streams, rivers, lakes, and along shorelines. However, riparian
vegetation remains relatively unprotected from poor agricultural
practices, residential and commercial construction, landscaping,
and logging. In recognition of this, the King County Sensitive Areas
Code (SAC) requires the preservation of riparian vegetation along
streams, around wetlands, and in other sensitive areas in order
to protect the water quality and habitat value of these areas. In
addition, King County Water and Land Resources restores riparian
areas that have been damaged through restoration projects and volunteer
replanting projects. |
