Shoreline Erosion

Is your house getting closer to the lake each year as your shoreline erodes? Several factors contribute to this type of erosion. Wave action from wind, boats and storms can destroy the shoreline. As these waves crash into the unprotected shore, shoreline sediments are washed into the lake and re-deposited elsewhere. Fluctuating lake levels are one of the most common causes of shoreline erosion. Since most of the lakes in Missouri are man made reservoirs, the vegetation growing on the lake’s edge is often not suited to alternating wet/dry conditions. As the water level rises, it covers the roots of upland trees and grasses. Then the water-covered roots don’t get enough oxygen. If that doesn’t kill the plants, the roots are then exposed by erosion when the water recedes.

Before you begin an erosion control project…

First, step back, and determine the cause and extent of shoreline erosion at your lake. Is this due to wind action? If so, maybe only the windward side is affected, and there may not be anything you and your lake organization can do to prevent it. Is the erosion caused by boat action, construction, or ice? Perhaps no-wake zones, construction ordinances, or ice break-up would address these issues.
Next, is the problem serious enough to address? How much of the shoreline has an erosion problem? What is different in the areas that don’t seem to be eroding? Are all the property owners willing and able to address this problem?

Last, what is the overall goal for the lake? Is this lake primarily used as a fishing, boating, swimming or drinking water lake? How do the lake owners want the lake to look; natural with a vegetated boarder, reinforced with a seawall, rock riprap, or some of each?

Methods of Erosion Control

The three types of standard erosion control are vegetative, structural, and combination. None of these methods is right for all situations. It is important to match the type of erosion, and lakeshore environment, to the control method.

Vegetative erosion control is the use of native plants and trees to stabilize the soil near the shore. Cattails and reeds can be used in the water to lessen the effects of wave action. These plants are very hardy and can withstand changes in lake water levels. On shore, landowners can use shrubs, willows, to shade the lot and reduce erosion.

Vegetative – Advantages

Trees shade the lake. This can lower water temperatures.
Increased spawning ground for fish.
Cuts down on mowing, and therefore less maintenance.
Soil and fertilizers are filtered through buffer strip, so less ends up in the lake.
Ducks favor this type of habitat – less food source for geese.

 

Vegetative – Disadvantages

Increases chance encounter with water snakes, ticks.
Does not provide “neat” shoreline view with park-like grass.

Structural erosion control involves building either a sea wall or the placement of rock riprap. Use of riprap is the most common type of erosion control. It involves the positioning of rock on the shoreline, often over a special filter cloth. Rock size is dependent on wave height, and bank slope. Obviously, the harder the waves are hitting the shore, the bigger the rock size required. This type of construction requires a 404 permit from the Corps of Engineers, and a 401 permit from the Department of Natural Resources.

Riprap – Advantages

Provides some structure for smaller fish/crayfish species.
May prevent further erosion of site, if correctly installed.
May provide immediate erosion control – reduced wave action.

 

Riprap– Disadvantages

Riprap protects only the land immediately behind the barrier, and not the adjacent areas. In fact, erosion may increase by wave reflection from the structure.
Riprap does not reduce water temperature, or filter soil from the land above the lake.
Riprap must be done correctly to have desired effect, the initial cost is high, and it does require maintenance as rock settle and fall into the lake.
Riprap does not maintain natural look of the lake.
Lakes with a riprap shore are less likely to have ducks or geese – waterfowl like to be able to walk out of water.

Combination of shoreline erosion control uses both of the previous methods. Riprap is first installed on the site, with soil added to the areas away from the water's edge. Tree plantings are then scattered within the rock riprap. Permits are required for this type of construction.

Combination– Advantages

Immediate erosion control, with future benefits of vegetation.

 

Combination– Disadvantages

Most expensive, since you have to do both riprap and plantings. Choose plants, such as willows, that are able to withstand fluctuations in water level.
Combination does require some maintenance to keep trees and rock in place. Usually only one tree species is planted on the site.

By stabilizing your shoreline you can prevent loss of property, and improve water clarity. The trick is knowing which method is right for your situation.

   

For more information, check out these websites.

www.bbmwd.org/erosion_control.htm

(LMVP edit - the other links have expired and have been removed)

Georganne Bowman

 

For more information, click this link

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