Stream banks and shorelines: erosion control
Living on the shore of a lake or river allows homeowners and renters to experience captivating scenery, unique wildlife and vegetation, recreational activities like boating and fishing, and so much more. It’s important to protect our shorelines from erosion so that these grand environments are accessible for generations to come.
What constitutes severe shoreline erosion?
If you own property with a streambank or shoreline and have the following issues, you may have what Wisconsin’s Department of Natural Resources (WI DNR) defines as a “Severe Shoreline Erosion” problem:
A large area of bare soil on a steep, high shoreline bank.
A measurable change of the shoreline over some time.
Leaning or downed trees with exposed roots on the shoreline.
Large patches of muddy water near a lakeshore, or unusually muddy streams during periods of high water or following a rainstorm.
Excessive deposits of sand or other sediments on the streambed, or very wide, shallow areas in a stream.*
*Causes of lakeshore and streambank erosion | Waterway protection | Wisconsin DNR
Why is severe Shoreline and Streambank Erosion a problem?
Shoreline erosion is problematic for a number of reasons:
Actively eroding shoreline and streambanks can:
Undercut and weaken infrastructure that is near the waterbody, such as bridges and buildings;
Lead to a loss of shoreline; and
Add sediment to the waterway, creating increased sediment pollution.
Sediment accumulation and deposition can:
fill reservoirs and dams with sediment, reducing holding capacity and efficiency that can lead to infrastructure failure;
clog streams and drainage paths, leading to overflow and causing localized flooding; and
extend shorelines and change the shape of the waterbody
Excessive suspended sediment can:
negatively impact fisheries and exacerbate algae growth;
limit recreational activities like boating and fishing; and
make water treatment processes longer and more expensive.
What causes Streambank and Shoreline Erosion?
Poor stormwater management
When stormwater lands on impervious surfaces and is directed into one path, (such as out of a downspout), the volume and speed of that water dramatically increases. A large amount of quickly moving water is very efficient at wearing away the land and depositing sediment into a waterbody.
Removal of native vegetation and shoreland material
Exposed soil surfaces have little to no protection or structural stability, so they are highly susceptible to wave, wind, rain, and runoff erosion.
Human Activity
Excessive or chronic activity close to the shoreline can loosen the soil. Highly foot trafficked areas can cause shorelines to destabilize, while recreational activities like boating create consistent and continuous waves that batter the shore.
Just one of these issues on its own can cause a problem, but if left untreated, they can grow and combine to have disastrous consequences. For example, poor stormwater management may channelize runoff in an area with no native vegetation, creating gullies that get bigger each time it rains. You can imagine how this can quickly get out of control.
How can Streambank and Shoreline Erosion be mitigated?
The best way to control shoreline erosion is often to use solutions that mimic natural processes. While you will need to assess your situation to find the right suite of practices for your situation, examples include:
Proper stormwater management
Collect, contain, infiltrate. Redirect stormwater runoff from impervious surfaces away from the shoreline, especially on steep slopes to avoid gully or rill formation. Use green infrastructure like rain barrels and rain gardens to help manage stormwater where it falls, learn more here! Runoff velocity and volume are typically highest during the rainy season, so having collection and infiltration devices ready at this time is helpful.
Reduced disturbance
Less disturbance means less dislodged sediment. Try to avoid walking along slopes or in sensitive areas along the shore. Once the sediment is dislodged, it is easily carried away and there’s no way to naturally replace it. Avoid doing any type of construction within 100 feet of the shoreline, especially bluffs, for they are at a high risk for collapsing.
Use of Riprap, Vegetation, and other Tools
Riprap, or large rocks and boulders, stabilize shorelines and reduce shoreline erosion by acting as an “armor” for the sensitive soil surface. This technique should be used with care, as it can change the nearby aquatic habitat and cause erosion / sediment deposition to occur in other unexpected locations.
Plants vary widely in physiology and functionality, so using a variety of plants along the shoreline helps manage stormwater and protects the soil. Native grasses are good for covering and stabilizing exposed and near-surface soil. Trees offer enhanced infiltration, soil surface protection, and deep-ground soil stabilization. Aquatic vegetation can help settle sediment and reduce the speed of waves and the current.
To learn more about vegetated armoring control, click here.
Riparian Zone: the area of banks and shores where land and river/lake interact, the junction of terrestrial and aquatic environments.
Shoreline and Streambank Erosion: the process of soil and sediment dislodgement and fragmentation along lakeshores and streambanks.
How an eroding lakeshore can cause problems downstream.
Severe lakeshore erosion along a bank.
How can I get started?
Before starting any erosion control measures construction, make sure you know what specific kind of shoreline erosion problem you are facing, what measures are needed to help fix that issue, and what permits you need to start a project. If your initial erosion assessment is incorrect or premature, you can spend time and money on an erosion control device that does not help your issue. In many cases, hiring a professional will produce the best results.
Working and doing any kind of construction within close proximity to waterways almost always requires a permit. Permit requirements vary widely and change depending on designated water body type, type of construction / installation, and location of construction. To learn more about what permits are required for activity around waterways and how to complete them, go to the Wisconsin DNR Waterways Permitting Process webpage.
If you live on a lake or river, be a good neighbor to this freshwater resource and to the rest of the community that depends on it. We all share the same water resources, making it the responsibility of all to manage shorelines and streambanks in an environmentally conscious manner.
Addition Resources
Lakeshore and Streambank Erosion- causes, identifiers, and control methods for shoreline erosion provided by the WI DNR.
Wisconsin County Code Administrators - find information regarding planning and zoning permits categorized by county in Wisconsin.
General Waterways- WI DNR gives information and links to preserving water for different types of projects: construction, shoreline protection, water level, crossing, recreation, and habitat.
Erosion Energy Calculator- a WI DNR resource used to calculate energy along a shoreline.
Erosion Control on the Great Lakes- the WI DNR’s directions on how to and necessary permits required for shoreline erosion control for properties along the Great Lakes.
Respect Our Waters
info@respectourwaters.org
Milwaukee area offices:
600 East Greenfield
Milwaukee, Wisconsin 53204
414.382.1766
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