Landscapers often encounter obvious and not so obvious slopes in commercial and residential lawns and landscapes. These slopes are prone to erosion, which not only results in an unsightly lawn profile, but can also result in various problems, including washing away valuable topsoil and the runoff of pesticides into storm drains and waterways, potentially polluting drinking water and harming aquatic wildlife.
How to deal with slopes has as much to do with the degree of slope and accessibility of equipment as it does the location. Different states have different regulations regarding erosion control, so it’s important to have a knowledge of state and local guidelines as well as EPA regulations before bidding on a job.
“In a bidding economy where margins are slim and penalties are shared by contractual obligation, an EPA fine can be the end of a company,” says Austin D. Edwards, president of Emerald Inc., in Elk Grove, Calif.
“It’s better to do the right thing and comply with the law than to get a fine.”
Natural and human influences.
Erosion is a naturally occurring phenomenon that is often initiated and/or made worse by human influences. In nature, it’s influenced mostly by wind, rain and spring runoff. Human-caused erosion can be traced to the use of heavy equipment for different construction projects. Erosion can also be caused by a simple case of neglect, e.g., not providing the proper vegetation to control and prevent it.
Mudslides and the wholesale washing away of plants and soil are an obvious, if not extreme, example of soil erosion. However, don’t rule out the more subtle signs of erosion – exposed tree roots, soil accumulating at the bottom of a slope and the splashing of soil on objects in the landscape.
Methods used to control erosion depend on the degree of the slope. Gradual slopes that are hardly noticeable to the eye simply require seeding with a hydroseeder over a prepared seed bed. Steeper slopes will require more material, equipment and manpower.
Hydroseeding is a practical method on sites with gradual slopes and where a hydroseeder can gain reasonable access to the site. Steep slopes are another matter.
“Some slopes are just too steep to assure good adherence of a hydraulically applied product,” Edwards says. He says geotextile products can be superior on steep slopes due to its immediate pinning of erodible soils. “Oftentimes, we combine both seeding and RECP’s (rolled erosion control products) to create a vegetated geogrid.”
Edwards says, where possible, he’d choose the cost saving potential of hydroseeding over RECPs. “On average, you get permanent hydroseeding for a quarter of the cost of a RECP,” Edwards says. “With the very best form of erosion control being natural vegetation, and the cost of hydroseeding being the value of engineering solution, we often try to use this option where practical.”
Edwards says hydromulch is also used in erosion control, but only as a preventative measure to control the erosion that can occur from a single rain event.
Ben Carter of Carter Land Services in Jesup, Ga., uses mostly sod to control slopes that are hardly comparable to those found in mountainous California.
“Typically sod is used, which is about the extent of our erosion control issues because we’re so flat,” Carter says. However, like Emerald, he needs to be certified and knowledgeable about the effects of water runoff, especially working along coastal Georgia.
Erosion control products.
There are more biodegradable products available these days to meet the increasingly stringent regulatory guidelines for erosion control. Excel S-2, manufactured by Western Excelsior, is one such example of a biodegradable RECP, which is made from shredded wood fiber sandwiched between two layers of stitched natural netting. Edwards says they use it to stabilize slopes and channels while also providing protection to freshly seeded areas so seeds can germinate.
A cheaper, less acceptable, but also less permanent product for environmentally friendly erosion control are slope interruption devices, commonly referred to as wattles. Wattles are elongated tubes made of compacted straw and other fibers that are installed along contours or at the base of slopes to help reduce soil erosion and capture sediment.
Wattles are mostly used as a temporary option. Earth Saver and other companies make photodegradable wattles that easily degrade from the UV rays of the sun. Edwards says the preferred bioproduct for the market he serves in the Sacramento area is Terra-Tubes.
These consist of tubes filled with straw fiber and wrapped in burlap. He says they eventually break down, leaving no material behind that could pose a threat to wildlife. Carter uses a jute matting to keep erosion in check on what is much flatter terrain than what Edwards and others deal with. His crew rolls it out over an area that has been graded and seeded to stabilize the slope.
Like any potential project, companies need to discuss erosion control options with clients, whether they be residential, municipal or commercial. Discuss cost, risk tolerance and other concerns they may have before taking on a job.
Following the rules and regulations, using the best tools and materials and communicating with the property owner will keep you off a slippery slope and ensure maximum profits.
The author is a horticulturist and freelance writer based in Sault Ste. Marie, Mich.