Water Quality Protected by Modern Forestry Practices

March 8, 2018
Stream buffer at Needle Branch unit

Modern stream buffer at Needle Branch unit helps to protect water quality after harvest

A recent study suggests that modern forest practices have little impact on water quality.  Current practices are governed by the Oregon Forest Practices Act which was developed after the Alsea Watershed Study was conducted in the Oregon Coast Range.  This study took place between 1959 and 1973 and revealed that some intense forestry practices at the time had negative impacts on water quality.  The latest rendition of the study, the Alsea Watershed Study Revisited, concluded in 2017 and yielded quite different results.

Outdated Forestry Practices Failed to Protect Water Quality

The studies monitored three watersheds that support a native fish population: Flynn Creek (untouched control), Deer Creek (partially logged), and Needle Branch Creek (clearcut logged).  During the first study, there were no streamside buffers along Needle Branch Creek.  Additionally, all large woody material was removed from the stream, and the clearcut site was burned.  After harvest, researchers found that the clearcut and burned watershed experienced increases in temperature and suspended sediment as well as a significant decrease in dissolved oxygen levels, an important measure for good fish habitat.  These changes were much more dramatic than those seen in Flynn Creek (untouched) and Deer Creek (partially harvested), showing that very intense forestry practices that mimic intense wildfires were not effective at protecting water quality.

Stream Buffer

Above is an example of a present-day stream buffer. Before the Oregon Forest Practices Act, this area would have been available for harvest. Now, this area is protected and helps to maintain the quality of nearby watersheds.

Modern Harvest with Streamside Buffers had Minimal Impact on Water Quality

About forty years after replanting, Needle Branch Creek was ready for another commercial harvest and the second study commenced.  In compliance with the Oregon Forest Practices Act, the harvest was completed in two phases; the upper portion in 2009 and the lower portion in 2014 and 2015.  This time, researchers left streamside buffers and did not remove any woody material from the stream.  After harvest, some slash was piled and burned.  This work plan gave researchers the opportunity to focus solely on the effects of the streamside protection buffers required by the Oregon Forest Practices Act.

Researchers studied the effects of streamside buffers on Needle Branch Creek as well as the two controls, taking over 4000 water samples between 2006 and 2017.  Their results showed that the clearcut harvest with streamside buffers had minimal impact on important measures of water quality such as suspended sediment concentrations and levels of dissolved oxygen.  In fact, suspended sediment concentrations in Needle Branch Creek were lower than that of the untouched control, Flynn Creek, both before and after harvest. This shows just how well streamside buffers protected stream quality following the second clearcut harvest in Needle Branch Creek.

This study is quite rare in that it has an extensive amount of historical data dating back to the 1950s.  This allows researchers to analyze changes in the watershed relative to precipitation levels, stream flow, and other environmental factors that change over time.  Given the extensive amount of data, researchers are very confident that improvements in stream quality can be directly tied to contemporary forest practices including streamside buffers.  This is a huge finding for our industry and as OSU professor and lead author on the study, Jeff Hatten, put it, “a good news story”.  According to Professor Hatten, “The primary driver of sediment flux is going to be climate; it’s going to be precipitation.”

So where do we go from here?

It is our hope that legislators will consider phase two of the Alsea Watershed study when reviewing the Oregon Forest Practices Act, just as they did with phase one in the 1970s.  Professor Hatten stated, “I hope it does come into conversation when drafting the next set of rules.  That’s why I do the work.  I want to impact society and have people make informed decisions.”  It is so great to know that we have such dedicated individuals sacrificing long hours to gather as much information as they can so that our community and our legislators can be armed with data and facts to make well-informed decisions about the future of forest practices in Oregon.