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A riparian/stream buffer is: (a) a strip of vegetated land
between a stream and adjacent upland; (b) an area maintained in permanent vegetation
(trees, shrubs, and/or grasses) and free from agricultural or urban encroachment, (c) an area
designed to intercept surface flow and groundwater flow from upland sources for the purpose
of removing or buffering the effects of associated nutrients, sediment, organic matter, toxins
and/or pathogens; and (d) an area managed to maintain the integrity of the channel and
floodplain ecosystem and their related habitats.
Thus, experimental findings from research on vegetated buffer are based on the functionality of a completely undeveloped buffer.
Whereas buffers represent the physical, on-the-ground systems that directly accomplish articulated goals (i.e. floodplain habitat, protection of riparian forests, water quality improvement), setbacks are the regulatory tools used to protect existing and potential lands from future encroachment. Thus, in order to achieve a desired ecosystem function or goal, setbacks in disturbed or built-out systems must be actively managed to function as buffers. Without out some sort of management (increasing pervious surfaces, planting native riparian vegetation, etc), setbacks alone are not likely to provide the desired ecosystem functions.
[Source: Memorandum from Balance Hyrdologics to the City of Berkeley Creeks Task Force, April 12, 2006.]
Regulations governing the use of private land within a specified distance of a watercourse, lake, wetland, or tidal shoreline have been in effect in many states and localities since the early 1960s. Such ''setbacks" or "buffer strips" serve diverse purposes, for example, protection of surface waters from pollution, protection of structures from flooding or erosion, and preservation of riparian habitat and shoreline amenities. One of the most prevalent features of the Memorandum of Agreement (MOA) Watershed Rules and Regulations is the use of setback distances for separating waterbodies from potentially polluting activities. Depending on the activity, 25–1,000 ft of land must separate the activity from nearby waterbodies. Greater distances are required for setbacks around reservoirs, reservoir stems, and controlled lakes than for those around wetlands and watercourses, which encompasses all perennial streams and in some cases intermittent streams.
Although the use of setbacks is quite common in watershed regulations across the country, little research has been done regarding the effectiveness of setbacks per se in preventing contamination of waterbodies from nonpoint source pollution. Rather, research has focused on the use of buffer zones for nonpoint source pollutant removal. Buffer zones are natural or managed areas used to protect an ecosystem or critical area from adjacent land uses or sources of pollution. They are an increasingly used best management practice (BMP) for many activities. Effective buffers along rivers, reservoirs, and lakes (riparian buffers) either retain or transform nonpoint source pollutants or produce a more favorable environment for aquatic ecosystem processes.
Setbacks, in contrast to buffer zones, are simply prescribed distances between pollutant sources and a resource or aquatic ecosystem that needs protection. Only if a setback is subject to management or natural preservation can it be considered a "buffer" that reliably insulates ecosystems and resources from nonpoint source pollution.
[Source: Watershed Management for Potable Water Supply: Assessing the New York City Strategy, Commission on Geosciences, Environment, and Resources, National Research Council, Washington, D.C.: National Academy Press, 2000, pages 427-428.]
