Riparian Buffer Study

GEI evaluated the costs and benefits of riparian buffers to protect Washington’s salmon habitat on agricultural lands. GEI prepared a draft model ordinance supported by science for counties to protect critical habitat.

Phase I of the GEI study documented the scientific literature on water quality protection, biological diversity, and fish habitat protection that riparian buffers provide to salmon-bearing streams. Best Management Practices (BMPs) for nutrients, chemicals, and livestock are the primary defense in protecting salmon in their habitat. Riparian vegetation can provide shade to maintain cool water temperatures but only the complete removal of vegetation demonstrated consistent thermal impacts. The role of large woody debris (LWD) to form habitat pools is important in high gradient mountain streams, but there is limited scientific evidence for measurable benefits of the LWD in lowland streams. Habitat in lowland streams may be protected in a variety of ways.

If mandatory 75-foot wide buffers were imposed in Washington, buffers could cost up to $81,000 for lost crops; $88,000 for lost dairy; and $93,000 for reduced land value per mile of stream.

In Phase II, GEI documented the science to support the following recommendations:

• Most agricultural type impacts to stream habitat could be largely mitigated with buffers of 10 - 25 meters
• Large wood and shade are site-specific and vary by species and habitat
• County ordinances should consider slope, precipitation, and the use of BMPs
• Voluntary cost-share programs such as CREP (Conservation Reserve Enhancement Program) will obtain broader participation and success then just regulatory measures.