Each waterbody is unique and options for buffer restoration will vary for each
A successful buffer restoration project should start with a thorough and honest assessment of the “lay of the land”: How much space can you realistically devote to your buffer? What are the site conditions that will shape or limit your options? How is the area currently being used? What is your budget? And what is your capacity for ongoing maintenance of the site? Your answers to these questions will shape your options and eventual plans for your buffer.
Generally speaking, the wider the buffer the better (with 100-200 feet being ideal for water quality and habitat benefits.) However, current land use—particularly if your restored buffer is in a public park or highly used or trafficked space—may limit the area you are able to devote to buffer restoration.
Keep in mind that a well-designed buffer can enhance most spaces by improving water quality, creating habitat for birds and other wildlife, and adding a variety of beautiful vegetation. “Carve outs” or small openings in your buffer can be incorporated into the design to maintain viewsheds and public access to a waterbody. And, interpretive signage can create opportunities for public education about the functions and value of the buffer.
One of the first questions to answer will be: how much area can I devote to the buffer? Once you know how much space you have to work with, you can start brainstorming and visualizing other aspects of your buffer design.
Nearby topography, and the slope of the land in your buffer area will shape the look of your buffer and eventual plant selection. Steeply sloped banks are more susceptible to erosion, which will make options like seeding more of a challenge.
If your streambank or shoreline is heavily eroded, you may need to consider an alternate location, as rapidly eroding banks may undermine seedlings. Streambank stabilization may need to occur prior to, or as a first step in, your riparian buffer restoration.
The pH of the soil in your buffer area and its composition will determine what types of plants to use. Well-drained sandy soils (common in our region) absorb runoff more quickly than more slowly drained soils; due to this, a smaller buffer width may work well in areas where sandy soils are present, while a wider buffer may be needed for sites with poorly drained soils.
How frequently the buffer area floods and how long it retains standing water will impact plant selection and other design choices in your buffer. If your buffer area is frequently under water, you will need to choose plants that can withstand periods of “wet feet.” Many conservation seed mixes are tailored specifically for riparian or coastal conditions where flooding is a common occurrence.
Take note of the weather conditions that your buffer is likely to experience throughout the entire year. How much sunlight or shade will the buffer receive? Is the buffer area subject to frequent strong winds, which are common along coastal areas, lakes and larger ponds? In coastal areas, winds may be accompanied with a salty sea spray. Be sure to choose plantings that will do well in the weather conditions your buffer is likely to experience.
All buffers require some level of maintenance, which will need to be taken into consideration at the design stage and budgeted for through the life of the buffer. Depending on the size and complexity of your buffer, as well as the types of invasives present in your area, maintenance can be performed by a homeowner, municipal staff, volunteers or landscape professionals.
Maintenance for a “no mow” buffer can be as simple as mowing to a height of 6-8 inches once or twice a year to prevent woody vegetation and small trees from “taking root”. You will also want to selectively remove any invasive plants.
Maintenance will be more intense in the early years, as new plants and seeds may require watering until established. (Trees and shrubs may require watering for the first three years during dry periods.) Once the trees are mature, they will shade out many of the competing weeds.
For municipalities: be sure to involve public works and parks staff—or whomever will be responsible for maintenance—in the design of your buffer project.
While the possibilities for buffer size and design are limitless, budgets usually are not. The three questions to ask regarding your budget are: how much do I already have to spend, and how much can I add or do I need to raise funds (through grants, donations, etc.) for the proposed project. A simple “no mow” buffer is likely the least expensive option, while more complex mixed vegetation plantings will require more design and purchasing of plants. For larger buffer projects you may need to hire designers and landscape professionals. And, regardless of the type of buffer, some level of maintenance will be required over the life of the buffer, which should also be included in your overall project budget.
What plant communities are already present? Take advantage of what you already have in place, as the vegetation already growing in your buffer is obviously well-suited to and likely to thrive in that location. Native plant species will require less water and less fertilization than ornamental non-native species, and for this reason are preferred for buffer plantings.
Your goals for the site, current uses and how you want the buffer to look will drive your decisions about what stays and what plants you’ll add. The good news is: there is no shortage of options when it comes to plants, just be sure to choose plant communities that are well suited to the specific conditions of your buffer location.
GOALS FOR THE SITE
There are several potential benefits of restored and improved riparian and coastal buffers, but what are YOUR goals for the project? And, how will those goals and the relative importance of the various benefits shape the decisions about your buffer size, design and other factors?
If reducing pollution and improving water quality is your primary goal, focus on making the buffer as wide as possible. Studies show that wider buffers are more effective at filtering pollutants such as nitrogen. Buffer widths of 30-100 feet may be ideal for sediment removal, while 150-160 feet may be ideal for removal of nitrogen.
Runoff will move faster in buffers with steeper slopes, so if you have a particularly steep slope, a wider buffer will be needed to achieve the same pollutant removal benefit. Soil type will also influence the pollution removal potential of your buffer; soils high in clay are less permeable and increase runoff, while very sandy soils may drain too rapidly for roots to trap pollutants. Moist acidic soils have been found to be better at removing nitrogen from the soil and releasing it to the atmosphere (a process known as “denitrification”).
Shrubs and trees, with more extensive root systems, will increase the pollutant removal potential of your buffer. Leaves and downed sticks and limbs will provide a physical barrier to slow sediment runoff, which also captures pollutants such as phosphorus which often bind to sediment.
During flood events, buffers and wetlands can slow runoff and absorb excess water. Downstream riparian buffers may be more effective in reducing flooding than upstream buffers. Buffer width will ideally match the width of the floodplain.
If your goal is to reduce erosion and stabilize your streambank, be sure to include plenty of woody plants, such as trees and shrubs. Their more extensive root system will reach deeper into the soil and help to stabilize your bank. Note that if the cause of erosion results from uncontrolled stormwater or other activities occurring above the bank, to achieve long term bank stabilization, the cause must be managed or stopped. If stormwater runoff is eroding the bank, divert the stormwater further inland to a rain garden or a depression to slow the runoff and allow it to infiltrate. If the erosion is severe, it may require a combination of engineered solutions along with planting vegetation.
Buffer width will also impact the quality of habitat in your buffer for both aquatic and terrestrial species. Studies show that buffer widths of 35-160 feet are ideal for protecting aquatic species such as trout and invertebrates, with widths of 200-300 feet providing maximum benefit for certain mammals and birds.
A mix of vegetation—including flowering plants, grasses, shrubs and trees—will help attract a variety of species to your buffer. Organic matter such as leaves, twigs and logs provide food and habitat for smaller species, such as insects, which in turn help to attract other wildlife. (Keep this in mind as you’re developing your maintenance plan, as you’ll want to leave much of your leaf litter and organic matter in place to maximize both the capacity for pollutant removal and the habitat benefits of your buffer.)
If the look of your buffer is a primary concern, which is common in public spaces such as parks, you may want to choose specific plant communities that add good color and visual interest to your buffer. Selecting plants that flower or provide color at different times of year will benefit wildlife that depend on plants for different life stages as well as provide year-round visual interest. You may choose to go with a “tiered” look, with taller vegetation such as trees and shrubs at the back (water side) of your buffer, and lower flowering plants in the front. If maintaining views of the waterbody is important, you may want some sections that are planted with grasses or seed mixes that can be mowed to a height of 6-8 inches once or twice a year.
Buffers can also be a tool for public education and engagement, particularly when located in a park or other space with lots of visitors. If you want to maintain access to the water, small “carve outs” or paths should be incorporated into your design. Interpretive signage can help educate visitors about the role and function of the buffer, as well as point out some of the vegetation and wildlife that visitors are likely to encounter.
You may also be able to engage with community and volunteer groups on the care and maintenance of your buffer. Volunteers can help with plantings, as well as periodic cleanups and maintenance.