By Karl Russek and Karena DiLeo
Chances are you’ve heard us use the term “riparian buffer” before, and you probably have a general idea it concerns keeping trees and shrubs along streams. But why are so they important, and how do they work?
A riparian buffer is an area adjacent to a stream, lake, or wetland that contains a combination of trees, shrubs, and other perennial plants and is managed primarily to provide conservation benefits. A wide variety of state and federal programs support the installation of riparian forest buffers on public and private lands.
Riparian buffers are the among the most cost-effective protection for our water resources. These strips of grass, shrubs, and/or trees along the banks of rivers and streams filter polluted runoff and provide a transition zone between water and human land use. Buffers are also complex ecosystems in their own right that provide habitat and improve the stream communities they shelter. Natural riparian buffers have been lost due to agriculture and development in many places over the years. Restoring them is an important step forward for water quality, riverbank stability, and wildlife.
BUFFER BENEFITS AND HOW THEY WORK
These are some of the main benefits:
Sediment Filter
Riparian buffers help catch and filter out sediment and debris from surface runoff. Depending upon the width and complexity of the buffer, 50–100% of the sediments and the nutrients attached to them can settle out and be absorbed as buffer plants slow sediment-laden runoff waters. Wider, forested buffers are more effective than narrow, grassy buffers.
Pollution Filter, Transformer, and Sink
Riparian buffers trap pollutants that would otherwise wash into surface and groundwater. Phosphorus and nitrogen from fertilizer and animal waste can become pollutants if more is applied to the land than plants can use. Because excess phosphorus bonds to soil particles, 80–85% can be captured when sediment is filtered out of surface water runoff by passing through the buffer. Chemical and biological activity in soil, particularly of streamside forests, can capture and transform nitrogen and other pollutants into less harmful forms. These buffers also act as a “sink” when nutrients and excess water are taken up by root systems and stored in the biomass of trees.
Better Aquatic Habitat
Forested riparian buffers benefit aquatic habitat by improving the quality of nearby waters through shading, filtering, and moderating stream flow. Shade in summer means cooler, more even water temperatures, especially on small streams. Cooler water holds more oxygen and reduces stress on fish and other aquatic creatures. A few degrees difference in water temperature can have a major effect on their survival. Woody debris feeds the aquatic food web. It also can create more complex habitat, providing cover for fish and their food supply while reducing erosion by slowing flow.
Stream Flow Regulator
By slowing the velocity of runoff, the riparian buffer allows water to infiltrate the soil and recharge the groundwater supply. Groundwater will reach a stream or river at a much slower rate, and over a longer period of time, than if it had entered the river as surface runoff. This helps control flooding and maintain stream flow during the driest times of the year.
Bank Stabilizer
Woody buffer vegetation helps to stabilize streambanks and reduce erosion. Roots hold bank soil together, and stems protect banks by diffusing the energy of flood waters. Buffers can also reduce the amount of streambed “scour” by absorbing surface water runoff and slowing water velocity. When plant cover is removed, more surface water reaches the stream more quickly, causing the stream to be more “flashy” and mobilizing sediment and nutrients from the banks.
Wildlife Habitat
The distinctive habitat offered by riparian buffers is home to a multitude of plant and animal species, including some rarely found outside this narrow band of land influenced by a stream. Continuous stretches of riparian buffer also serve as wildlife travel corridors.
If you have a lake, stream, or wetland on your property and you’d like to know more about improving your riparian buffers, French & Pickering can help! Please contact Karena at kdileo@frenchandpickering.org or Karl at krussek@frenchandpickering.org.
