Merriam Webster’s dictionary definition for seawall is “a wall or embankment to protect the shore from erosion or to act as a breakwater”. However, these very seawalls are degrading natural shorelines, eliminating native plant and wildlife species, and creating worse erosion than if the natural environment had been left untouched. The National Lake Assessment (NLA) is a survey conducted under the Environmental Protection Agency (EPA) that records the condition and health of our nation’s lakes, ponds, and water reservoirs. In Michigan, home to 84% of North America’s surface fresh water, over 50% of inland lakes are facing stressors due to lakeshore habitat loss.
Many homeowners are drawn to lakefront properties for the undeniable beauty and serenity that come with these large bodies of water. Unfortunately, a shoreline without such development is a healthier shoreline. Without infrastructure, the natural vegetation is allowed to grow into three full tiers: trees, shrubs, and aquatic plants. With development comes more ornamentals, mowed lawns, and an increase in impervious surfaces, such as parking lots, driveways, and roofs. These hard surfaces don’t allow for surface water to filter slowly into the ground, but rather make an easy direct route for pollution to flow into our waters. The plants we oftentimes confuse for “weeds” at these sites are busy supporting soils and large populations of fish and wildlife. The two most destructive activities to a shoreline ecosystem are removal of the native vegetation and the application of seawalls.
Hard-engineered seawalls create a rigid barrier that generates “scouring” in the water. Scouring takes place when wave energy hits a seawall and has no way to dissipate the remaining energy. This in turn directs a rush of energy down and sideways, pushing sediment and lake bottom deeper and deeper, resulting in loss of habitat and extreme erosion. Bio-engineered shoreline solutions can be an effective alternative and overall greater success than installation of a seawall.
Using biodegradable shorelines, native plants, and erosion control blankets, we are able to recreate the shoreline’s bank and maintain the integrity of natural shorelines. This is often a more cost-effective route and a more ecologically-friendly one. At some shoreline sites, the erosion rate can be drastic and easily distinguishable. In others, using the ordinary high water mark (OHWM) of a body of water can illustrate the shoreline’s recession over time. The ordinary high water mark is defined as, “the line between upland and bottomland that persists through successive changes in water levels, below which the presence and action of the water is so common or recurrent that the character of the land is marked distinctly from the upland and is apparent in the soil itself, the configuration of the surface of the soil, and the vegetation” (NREPA Part 301). The OHWM should be used as a guiding factor in designing a natural shoreline project. It will illustrate where the shoreline naturally extends up to and where it should not exceed.
Common materials for re-creating a natural shoreline include coir logs, erosion control blankets, rip rap, stakes, and native plants. Starting at the point farthest from the shore, erosion can be controlled with no-mow practices. Not only is the turfgrass that is often used for lawns unstable but also short and weak because of their shallow root systems. Such grass cannot withstand the energy that comes from waves, ice push, and wind. Mowing the already short and weak turfgrass continues to increase the chance of substantial erosion. As you move closer to the water’s edge, plantings that will restore the integrity of the soil and root structure should be planted into an erosion control blanket. This woven or layered fibrous blanket protects the seeds and plantings during their fragile establishment period. Made from biodegradable materials, this blanket will then break down naturally and does not need to be maintained. Like erosion control blankets, coir logs are available in a range of diameters, densities, and lengths. These should be placed where they can most optimally protect the toe and slope of a shoreline. Both the fiber logs and erosion control blankets can be staked in with wooden stakes and secured with rope. The last part of restoring a natural shoreline is installing rip rap (rock) on either side of the coir logs to ensure stability. Aquatic plants can then be planted directly into the coir log, or into the water itself on the other side, to establish a bed of native plant growth. While each shoreline is different, and sites may vary in materials and design, the above outlines a very generic shoreline restoration project.
It is also important to research your area’s permitting and certification processes. In the state of Michigan, shoreline project permits almost always must be filed through the Environment, Great Lakes and Energy Department (EGLE) and approved before construction begins. There are also regulations that say what and where you can plant native plants along the shore. These things should be addressed before anything on the ground is altered. Lastly, the most important part of a shoreline project is the maintenance that must occur long after the project has ceased. This can include health inspections of the colonizing plants, control of any invasive species, evaluation of the bioengineered materials, etc. This can all be monitored through site visits, field logs, and photo books. Closely monitoring a site is critical in the long-term success of a shoreline project. Without it, the site could easily fall under to the immense erosive forces that had washed it away initially.
Shorelines are constantly evolving. Becoming completely reshaped with the movement of waves, storms, and climate change. Managing for those changes while also preventing shorelines from disappearing all together is the ultimate goal. Finding where that site’s sustainable water level is and then meeting the habitat needs of those wetland-dependent wildlife and plant species is critical.
You can find out more about shoreline restoration information at: http://www.mishorelinepartnership.org/
Do you know anyone that has a seawall? Have their shorelines suffered because of it?
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