Riparian Buffers and their importance

Published 9:05 am Friday, July 26, 2013

With the recent abundance of rain in the area and especially with the erosion that follows, it seems a perfect time to discuss the importance of riparian buffers.

First, what is a riparian buffer? A riparian buffer is the vegetated land adjacent to a stream or water body. This vegetation benefits water quality and habitat by helping to regulate temperature, add organic matter (leaves and twigs), assist in pollution reduction and by providing wildlife habitat.

Lack of riparian buffers along streams and water bodies result in excess stream bank erosion. Some stream bank erosion is a natural part of the down cutting process of waterways; however, this process is accelerated by altering the stream system in some way, such as straightening or widening, removing streamside vegetation and clearing for agriculture, forestry and/or development. Altering the natural system can result in erosion rate hundreds of times greater than those seen in naturally stable streams.

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Without proper riparian buffers, stream bank erosion and sedimentation of waterways is all too common. Sediment and other nonpoint source pollutants come from many sources and make their way into our waterways through surface runoff. When land disturbing activities occur, soil particles (sediment), nitrogen, phosphorus, pesticides and fecal coliform bacteria are transported by surface water and are often deposited into streams, lakes and wetlands. These pollutants can affect an aquatic ecosystem in a number of ways. Excess nutrients (nitrogen and phosphorus) can cause algal blooms, fecal coliform bacteria can be an indicator of waste-borne disease and pesticides can kill or sicken fish and aquatic invertebrates.

The loss of these valuable vegetative zones results in reduced water quality, reduced wildlife and fish populations, causes serious property damage (bank erosion), and loss of valuable agricultural lands. It also results in increased water temperatures and decreased dissolved oxygen in the water, decreasing aquatic life. The loss of shade by clearing along waterways exposes soils to drying by wind and sunlight and reduces the water storage ability of the riparian area. If there is not a buffer for runoff water to spread over, it can cut channels into the land, allowing the sediment and sediment-attached pollutants to flow directly into a stream or waterway. Sediment in our waterways is the largest single nonpoint source pollutant and one of the primary factors in the deterioration of surface water quality in the United States.

Riparian buffers are the most stable and effective ways to protect our streams and waterways. In North Carolina, natural riparian buffers are forested. They include a combination of native trees, shrubs, grasses and herbs that form a plant community adjacent to a stream or water body.

How do riparian buffers work? Buffer vegetation slows and filters runoff water above ground, causing sediment to settle out and be deposited in the buffer, not in our waterways. The vegetative buffer allows water to percolate through the soil into the groundwater table, instead of running over the surface of the land, picking up sediment in the process. In many locations, groundwater moves toward streams, and it often carries nitrate-nitrogen and sometimes pesticides. Nitrate, a pollutant that moves in groundwater, can be diluted in a riparian buffer. Plants use it, but more importantly, it is changed to nitrogen gas through denitrification, and nitrogen gas poses no harm to the environment. Riparian buffers that contain a diverse mixture of plants work the best, since different plants have different rooting structures. Some plants utilize the top several inches of soil, while others, such as taproots penetrate deeper into the soil. These roots not only remove nutrients but they  also sstabilize steam banks.

What are the benefits of having, preserving, and/or restoring riparian buffers? Buffers perform many environmentally, economically and socially significant functions. They maintain and improve water quality by protecting water resources from nonpoint pollutants from both urban and agricultural activities. Buffers slow floodwaters, thereby helping to maintain stable stream banks and protect downstream property. Slowing floodwaters allows the riparian zone to function as a site of sediment deposition, trapping sediments that build stream banks and would otherwise degrade streams and rivers. By slowing down floodwaters and rainwater runoff, riparian vegetation allows water to soak into the ground and recharge groundwater. Buffers shade streams and regulate fluctuations in water temperatures which help maintain fish habitat, especially for cold-water fish such as trout. Buffers can increase the amount and variety of wildlife and songbirds because they provide a wider range of  habitat and food and they are an important travel way for wildlife.