Environmental Insight With a Touch of Real Science
by Don Flora (a real scientist)
There is a plethora of literature on buffering along watered places. Little of it applies directly to Puget Sound. This is a brief discussion of why that is, the functions and values we expect from buffers, whether buffers can be expected to function well here, and some of the alternatives.
- Buffer studies around the world have focused largely on streams winding through farmland. Thus data on buffer effectiveness comes mostly from short-duration studies on deep, well-drained soils beneath pastures, feedlots, or bare-soil row-crop agriculture.Recent decades have brought buffer research to forest settings along back-country streams in the Northwest’s West Side. Some of those are mentioned here.
Literature compilations portray wide differences in effective buffer widths, reflecting not faulty research but rather compilers’ failure to indicate the field conditions that varied among studies. There is no ‘best’ buffer science.
In any case, buffering beside Puget Sound has had much advocacy but little study. In particular before/after research is seemingly absent altogether and with/without comparisons are few and somewhat confounded.
Buffers’ primary role is stopping or slowing overland and near-surface stormwater. This is important where nutrients, pathogens and toxics aren’t otherwise stopped.
Buffers work here: They slow or even stop sediments, which carry certain pollutants. By slowing stormwater they encourage infiltration to aquifers, which is either good or bad.
Buffers don’t work here: They don’t stop stormwater in places with combinations of steep slopes, hardpan (glacial till) soils, hard or prolonged rains, winter-dormant vegetation, limited low groundcover (as in shrub landscaping and woodlands). Dissolved pollutants travel on.
On balance, the Island may wish to include in its SMP (1) checking the performance of existing buffers and (2) considering the cost and effectiveness of alternatives, including halting pollutants at their sources.
If you prefer, you may download a PDF copy of the document.