Shoreline Stabilization

Shoreline stabilization

PADL members are asking how to stabilize their shoreline. PADL is looking into what type of plants are best to use.

Native vegetation can be added to your shoreline. The root systems trap sediment, keeping it on the shoreline where it belongs. Vegetation also dissipates the energy of a wave which reduces the impact of breakers. A wave crashes, hits the vegetation, gets slowed down, but the energy still flows forward eventually wearing itself out. Armored or rocked shorelines actually add to erosion as they fail to dissipate the wave energy and simply reflect it somewhere else. It is a simple property of physics – equal and opposite reaction. This ends up channeling the energy onto a less armored “weaker” shoreline which will end up eroding faster. This then will provide an access point for more wave energy to enter which eventually undermines the rocked edge as well. Rock has another problem in that it does not trap sediment very well like roots do. Water that crashes through the boulders eventually will reach the finer sediment on the shore which if exposed will get lifted away and flushed into the lake. Concrete walls cause the same thing. They too reflect wave energy and like rocked structures increase the erosional effects. This happens as the wave energy hits the wall and then cycles downward undermining the wall itself. Sediment is lost under and from behind the wall as gravity pulls down soils on the land to replace those that have been washed to the lake bed.

Best thing to remember is that vegetation holds soil, not rocks, and thus encouraging a richly intertwined root system of many different species of plants is nature’s way of holding soils in place. Of course trees do fall into streams and lakes over time, but this too is natural and serves an ecological need as well, providing habitat, etc. Nature acknowledges this by spreading more seeds upland to replace those that grew before. End of the day (on a geologic timescale) mountains wither to the sea, and erosion natural or man-made will do its best to tear down mountains or shorelines, vegetation is the buffering system though that slows this down (on the order of centuries and millennia). So best management practice (BMP) for your shoreline…let it go wild. Get rid of a lawn should you so have one in favor of shrubs and other plants that actually have decent sized root systems. Plant low growing willow trees as they tend to grow quickly, and have a great capacity to thatch together a root system. This will protect your shoreline and property as well as use up nutrients before they get into the lake. Devils Lake used to support Sitka Spruce trees 250’ tall, which grew everywhere (many still do where development has either not occurred or where they were spared), and they grew without fertilizer, so we know naturally there are nutrients available that can sustain large (enormous) native plants. Thanks again for your inquiries. Feel free to contact us anytime.

Sincerely,

Paul Robertson
Lake Manager
Devils Lake Water Improvement District

Visit us on the Web at www.DLWID.org

Minnesota
/www.shorelandmanagement.org/

Geosynthetic turf reinforcement mats (TRM)

www.astm.org/SNEWS/NOVEMBER_2000/nov_geo.html
www.geotextile.com/product.aspx?name=Turf+Reinforcement+Mats
www.geotextile.com/contactus.aspx?location=Oregon

Tensar wave barrier: On July 1, 1997, we installed “Tensar” fence with three-inch diameter size posts every ten feet as a wave barrier at approximately the mean tide level. It was secured to the post with 1” x 2” lathing and nailed at the top and bottom.

http://www.usfabricsinc.com/products/geotextiles.shtml?ex=eep549-5pxuxg-0&gclid=CPaxk6_dnZQCFREUiQod_gpX0g

Slopetame2 is much more than an erosion control blanket or mat. Slopetame2 is a permanent three-dimensional reinforcement and stabilization matrix for steep vegetated slopes and channel banks. The integral rings, bars, grid, and fabric act to contain upper root zone soils, allow vegetation roots to easily pass through, and minimize movement and loss by rain or flowing water. Slopetame2 is shipped in roll form, with connections allowing rolls to be fastened together forming one large continuous mat covering the entire face of long slopes. Rolls can also be pre-vegetated by vibrating sod into rings (or growing custom plant mixes in mat by contract), to allow mats to be placed and anchored to slopes with established root systems, able to withstand intense rainfall or water flow immediately. Holes can be cut in the mat to provide for large containerized or balled plant material.

http://soil.environmental-expert.com/STSE_resulteach_product.aspx?cid=8649&idprofile=3446&idproduct=8830

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P.O. Box 36
Lincoln City, OR 97367
PADLsteward@wcn.net