Protecting Creeks in Berkeley, CA; Value of Buffer Zones

On April 17, 2006, the Creeks Task Force of Berkeley, CA approved recommendations (PDF) to balance development with wetlands protection. Here are selected passages that have relevance to the debate over Northampton’s wetlands ordinances.

Wenger (1999) contains a review and synthesis of “over 140 articles and books…to establish a legally-defensible basis for determining riparian buffer width, extent and vegetation.” Wenger’s article was reviewed by a long list of other researchers in the field. With regard to the single issue of sediment control, Wenger says:

Scientific research has shown that vegetative buffers are effective at trapping sediment from runoff and at reducing channel erosion. Studies have yielded a range of recommendations for buffer widths; buffers as narrow as 4.6m (15 ft) have proven fairly effective in the short term, although wider buffers provide greater sediment control, especially on steeper slopes. Long-term studies suggest the need for much wider buffers. It appears that a 30 m (100 ft) buffer is sufficiently wide to trap sediments under most circumstances, although buffers should be extended for steeper slopes. An absolute minimum width would be 9 m (30 ft). To be most effective, buffers must extend along all streams, including intermittent and ephemeral channels.
The importance of small and intermittent streams was also discussed in Erman’s presentation to the CTF in July 2005. The CTF minutes for that presentation say “[Erman] explained that a lack of buffers on small streams in the headwaters with low or intermittent flows will lead to impairment of downstream waters despite buffers in the lower reaches of a watershed.”

As far as aquatic habitat, Wenger’s (1999) summary of the existing state of scientific knowledge is:

To maintain aquatic habitat, the literature indicates that 10-30 m (35-100 ft) native forested riparian buffers should be preserved or restored along all streams. This will provide stream temperature control and inputs of large woody debris and other organic matter necessary for aquatic organisms. While narrow buffers offer considerable habitat benefits to many species, protecting diverse terrestrial riparian wildlife communities requires some buffers of at least 100 meters (300 feet). To provide optimal habitat, native forest vegetation should be maintained or restored in all buffers.
Since environmental benefits of stream buffers continue to increase as buffer width increases, setback zones that are intended to preserve wilderness characteristics are often far wider than most of the widths discussed above. For instance, the logging plan for the Rogue River-Siskiyou National Forest requires a buffer zone of 348 feet on each side of both perennial and intermittent streams (Associated Press, 2005).

See also:

Intermittent Streams Merit a 100-Foot Buffer Zone in Hopkinton

Belchertown Wetlands Regulations

Benefits of Urban Wetlands and Their Buffer Areas

Maps: Millyard Brook and Surrounding Wetlands a Longstanding Feature of Ward 3