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 zone.

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 and shrubs.
      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 streams.
      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.