Between 1999-2001, over 100 digger logs were installed throughout Jonathan Creek, a small meandering tributary off of the Petitcodiac River. When installed and maintained correctly, a digger log will create a riffle upstream of the log, oxygenate the water, and create a downstream pool. These pools are especially important for cold water species like salmon who must rely on these small pockets of cold water refugia during hot summer days when water temperatures rise beyond their tolerance – an increasing concern that comes with climate change. However, when these in-stream structures are poorly installed, misplaced, or left in too long, they no longer serve their intended function and may in fact cause several serious unintended consequences including erosion, increased sedimentation, and more.
Sometimes well-meaning conservation projects can have unintended consequences. Ecosystems are fragile and highly complex; even with the help of modern science, there is still a lot for us all to learn. In 2020, PWA staff who were conducting culvert assessments and debris removal began to notice that there seemed to be increased erosion around several of these in-stream structures. Moreover, most of them never even succeeded in creating habitat pools. One of the biggest reasons for this failure was the placement of the logs. We now know that in most cases, there should be no more than a single digger log in a meander; however, in Jonathan Creek, many meanders featured several in close proximity.
Following this discovery, several years of painstaking assessment and log removal ensued. In total 17 logs across the upper and lower portions of the tributary were deemed problematic and removed.
Scientific discovery is an ongoing process and knowledge, technology, and best practices are always growing and changing as we learn. Mistakes will inevitably be made, and these mistakes will sometimes have consequences. What is important is that we learn from these mistakes and use them to improve future work. The PWA is always cautious and calculated when it comes to decision-making regarding our remediation work and also understands that it is our duty to ensure none of our projects cause long-term environmental harm. Follow-ups and monitoring help to make sure that any mistakes are caught and fixed. Over time, restoration methods change, new technology is created, and more knowledge is uncovered. Follow us on our learning journey on Instagram @petitcodiacwatershed or on Facebook at the Petitcodiac Watershed Alliance.
Since Jonathan creek flows into Jones Lake in Moncton, post a photo by the lake, tag us, and use #25watershedmoments to enter our giveaway!