Green Belt Riparian Zones
What is a Riparian Zone?
A Riparian Zone is the ribbon of vegetation adjacent to a shoreline or stream
bank. The grasses, shrubs and trees are typically different varieties than the
surrounding area. The riparian plant life is able to tolerate or needs a wetter
environment. Usually these areas provide a home for an abundant variety of
wildlife. Many creatures live their entire lives completely within a riparian
What is the sponge effect?
Riparian zones soak up water with the help of the root structures of various
plants. This becomes a water storage area for nature and has a slowing effect on
runoff during the wet season and then contributes to the stream flow during the
dry season. Many streams have an adjacent swamp or wetland area. They are also
part of the natural water storage of the stream and it is important to leave
these areas undisturbed.
What is the filtering effect?
Development and modern society have created many things which have degraded
water quality. Runoff from lawns and farmland which have been fertilized can
impact water quality. Runoff which contains livestock fecal matter is an
obvious problem. Runoff from shopping center parking lots is just as bad. A
healthy and sufficiently wide riparian zone can trap sediments and filter many
of these contaminating agents. The plants, especially the grasses, are very
good at capturing, holding and mitigating some of the problem runoff that modern
society creates. The filtering effect can make a dramatic impact on a stream
and is an important reason to leave these riparian areas intact.
Why is tree shade important?
For the salmon, steelhead and trout to survive in our waters, it is important to
maintain the proper water temperatures. This is also true for the other aquatic
creatures and those who feed on them. The shade from the riparian zone trees
help keep the water cool and this helps maintain the proper dissolved oxygen
count. Proper tree shade can lower water temperature by as much as 10 degrees
Fahrenheit. When you read about fish die offs it is usually due to insufficient
dissolved oxygen in the water. Most often the main cause is the water is simply
too warm. Excessively high water temperature is usually a combination of
factors: low water level, pollution, and a lack of shade. The most notable
trees in the local riparian zones are cottonwood plus Oregon ash, white alder
and willows which can appear as a shrub or a tree.
Will it help with erosion control?
A healthy riparian area can slow the water flow during a high water event. This
reduces the flash flooding downstream. It also reduces erosion which reduces
sediment in the water. A good healthy growth of native grasses, shrubs and
trees is the best way to control erosion. This alone is a good reason to
maintain healthy riparian areas.
What is Understory Vegetation?
Understory vegetation is the trees, bushes, vines and other plants underneath
the tree canopy. These plants help hold the soil in place during flooding and
even help slow the velocity of the water during flood events.
What does a healthy riparian zone look like?
In our area it should have a bountiful array of plant life including understory
plants and plenty of trees. The trees should shade the water to keep it cool.
There should be no contaminated runoff allowed to pollute the area. This would
include things like silt, livestock waste, fertilizers and pesticides. Runoff
from parking lots and city streets is also very dangerous for water quality and
should be controlled.
What about smaller streams?
The smaller streams are just as important, or more so, than the bigger creeks
and rivers. Almost all our water is carried from our lands and communities by
the small and sometimes intermittent streams. They are usually the ones most
likely to be abused or ignored and this is where our water quality is most
vulnerable. Some fish, like steelhead, can actually be spawned in intermittent
streams. These small stream riparian zones need to be protected.
What about the wetlands and springs?
Most rivers have adjacent ponds, wetlands and springs. This is a very important
part of the riparian system and should be dealt with accordingly. During the
dry summer months this becomes part of the stream flow and supplements the water
level and maintains the water flow. This also helps keep the water temperature
down and the dissolved oxygen count up and is a major factor in keeping the pH
in line. This process of storing water in the winter and then supplementing the
flow and helping to maintain better water quality is called the sponge effect.
What you can do.
· Protect existing plants along any stream and replant areas lacking trees
· Never pour oils, waste, or other chemicals down a storm drain. Storm
drains flow into the streams.
· Support efforts to prevent muddy or polluted runoff from entering the
· Do not relocate fish from one body of water into another, and never
release pets into the wild.
· Avoid damming up streams.
· Get involved! Learn more about riparian issues and make others aware.
Many groups are concerned about the quality of our water supply.