Stream Bank Stabilization
As a stream matures, it naturally changes its course and meanders. Water wears away soil and rock forming the banks and deposits it downstream over the course of hundreds of years. With the creation of drainage ditches, straightened streams and storm sewers, water is more efficiently routed into local streams. However, these changes cause the speed and velocity of stream flows to increase, particularly after heavy rainfall events. Additionally, as more paved surfaces are constructed, rainwater can no longer seep into the ground naturally. This causes the water to flow more rapidly into streams, resulting in erosion and cut banks. If proper preventative measures are not taken. this can have significant impacts on the property.
DuPage County has a County-wide stream maintenance program to reduce flood damages associated with debris jams and to restore the natural flood storage and movement of the streams. This program is in addition to the responsibilities of the owner of the property to maintain their section of stream (i.e. removal of debris and blockages). Periodic maintenance to prevent debris jams from accumulating is the best approach.
While some debris is naturally occurring - such as leaves or branches - some materials - such as tires or plastic bags - become detrimental to the stream ecosystem. In addition, some landowners store debris, including scrap lumber, firewood or leaf piles - streamside where they may be washed into the stream during times of peak flow. When this debris builds up, it can cause jams that restrict the water flow and increase water levels. This leads to further erosion of the stream bank and possible flooding during heavy rains.
Additionally, many people illegally dispose of yard waste in their streams. This is not recommended and strictly prohibited by law. Piled grass clippings kill underlying vegetation that help stabilize the stream bank. When these nutrient-rich clippings enter the water, they can also cause algae growth, odor issues and reduce the amount of oxygen in the water, which is detrimental to fish and other aquatic organisms. In addition, placing woody brush in or near a stream sets the stage for debris jams to occur, often resulting in localized flooding. If yard waste is disposed of illegally on a stream bank, the landowner will be asked to remove the debris and may be subject to a fine. Many units of government now offer assistance in the disposal of yard waste. For more information please contact your municipality, township or DuPage County.
Stream Bank Erosion
When attempts to stabilize eroded stream banks fail, they often result in adverse effects on neighboring properties as well. Before any stream bank stabilization project is initiated, the property owner should seek professional guidance on stabilization techniques, as well as information on floodplain and wetland permits.
Stream corridor landscaping is an effective method to slow down the rate of erosion. Using vegetation - rather than concrete, rock or wooden ties - as the primary means of stabilizing an eroded stream bank is usually a cost-effective alternative. By reintroducing native trees, shrubs, wildflowers and grasses along streams, a living system of stabilization will be created.
To begin stabilization, property owners should leave a buffer zone consisting of taller grasses and native plants of at least 5 to 10 feet between their mowed lawns and the stream. This helps reduce erosion, filter pollutants and improve wildlife habitat. Before any planting begins, the non-native vegetation - or exotic species - should be removed. This will allow more sunlight to reach the area and encourage the growth of native species. However, if removal includes larger shrubs, non-native plants should be replaced with similarly sized native species to replace habitat functions. Click
here for more information on non-native species and removal processes.
It is always important to develop a stabilization plan that will prevent erosion without impacting landowners up- or down- stream of the project. This work often requires a permit from municipal, county and federal agencies. Consulting a
list of professional engineer and environmental specialists familiar with DuPage County is recommended.
In cases of severe stream bank erosion where stream corridor landscaping has failed, bioengineering may be necessary. Engineering techniques and biological expertise are combined to control the erosion. Engineering considerations include the hydraulics of the flow and the structural integrity of the banks. Biological considerations include stabilizing vegetation. These techniques were designed specifically to reduce erosion and maintain a more natural stream without increasing flow or velocity. They protect both the natural beauty of the stream and the valuable properties alongside it. Stream banks stabilized with these methods are able to withstand heavy spring floods and other severe conditions. Structures, such as coir rolls, a-jacks and soil lifts, are installed at the toe of eroding banks. Native plantings and fast-rooting trees whose natural habitat is at the waters edge are built into the structure . Their roots bind and strengthen the banks as they grow. Finally, the banks are sloped, contoured and planted with other native water-loving vegetation.