Summertime in the Belgrades
June 29 – July 5
Buffers and Mulch
by Dale Finseth
This week I'll try and focus on two methods to slow down stormwater runoff. For those of you familiar with the LakeSmart program this will seem familiar.
Why slow down stormwater? Well, when we do get a rainstorm it often arrives with a great deal of rainfall in a short period of time. Over the past few years that seems to have been more the case. All that water running off our roof, driveway or other impervious surface, rushes downhill towards the lakes. In its travel it carries various chemicals and soil particles which, once they reach the lake, add silt, phosphorus, nitrogen or other toxins to our lake water. This article will focus on two methods for slowing that stormwater: vegetative buffers and mulching.
Vegetative buffers are located in the path of stormwater runoff to intercept the water, slow it down, and try and get the water to soak into the soils before it reaches the lake. Many of the plants in your buffer may be natural, but many properties may have most of the vegetation between their buildings and the water removed. A lawn is NOT an effective buffer. Water sheds off a lawn without being slowed much.
What most properties need include plants that will serve as a ground cover, plus some smaller shrubs and then larger trees. If this type of planting needs to be added, make sure you use native plants and plants appropriate for your property. Will they get enough sun? Will they grow in your soil conditions? Will you be prepared to manage their growth as they may demand?
Plant your plants in a manner to intercept the stormwater runoff. It also helps if you let the natural duff collect beneath your plants. It helps to slow runoff and soften the impact of water droplets to protect the soils beneath.
If you can, only maintain the needed pathways and open areas which you use. Many of us have more open space around the buildings and driveways than we use. Let it return to a relatively natural state. I've seen yards where people have swept the pine needles and other duff into piles and left the bare ground exposed. Avoid this type of practice. It can lead to stormwater runoff that is not impeded at all.
Mulch can best be used with your vegetative buffers. Erosion Control Mulch is the better type of mulch. Mulching is one of the most effective and cost efficient best management practices we should work with. For stabilizing construction sites, eroded banks, and topdressing buffer plantings, mulch is great in protecting water quality.
Mulch applied to an exposed site in the right amounts will serve several functions. A primary function is to protect the underlying soil from erosion and keep soil out of a water body. A secondary function occurs when a mulched area is located on the down side of a slope towards the water. The mulch will filter out most soil particles, fertilizers or toxins found in storm water runoff.
In some cases, a mulch berm between a driveway, lawn or parking lot and the water can be added to provide this filtration even if there is no exposed soil to cover. Another major benefit to mulching is the moisture holding capabilities of this product. Mulching landscaped areas with tree and shrub plantings ensures that water, either from rain or from a hose, will percolate to the roots and keep the soil cool and moist.
Mulch comes in many textures and colors. Sorting out the differences between "conservation mulch", "erosion control mulch", "bark mulch" and "wood chips" can become a daunting task.
Erosion control mulch (ECM) was developed to protect soil from erosion in areas that are heavily traveled, well exppsed to the elements, or steeply sloped. ECM, sometimes called "slope stabilizer," is not your standard landscape bark mulch.
The best way to describe ECM is "chunky". While regular bark mulch is fairly fine with strands of bark no longer than 6″, ECM has larger pieces of woody material, bark, and small stones. These small rocks mixed in with the bark provide additional structure to the product and add weight for keeping slopes intact.
One key to the effectiveness of ECM is the size and shape of the bark material. When applied, the long and thin material essentially weaves itself together and creates a kind of blanket over the soil. ECM traps plenty of moisture, like standard bark mulch. Thickness of application can vary depending upon several factors but 4-6″ is average. Sites with extreme exposure to wind and water may need more while mulch berms may be 18-24″ tall.
Buffer plantings plus ECM work very well. When the District installs a watershed buffer planting, ECM is what we mulch with. One important thing to remember is that 4″ is too much mulch around the trunk of a tree or shrub. Remember to pull back the top 2″ of material leaving 1-2″ around plants. If the look of the ECM is too chunky for your taste, putting an inch of standard landscaping bark mulch on top is fine.
Remember, there is a lot to do in working to protect water quality.
Conservation Too columns are written by staff at by the Kennebec County Soil and Water Conservation District in Augusta. For more information about the district and its projects, call Dale Finseth at