The Broken Brooks Project: Culvert Assessments
“Culverts are the most common structure used to enable anthropogenic transportation across waterways, and in the case of those culverts assessed in the Petitcodiac Watershed, pose either a partial or a full barrier to fish passage 75% of the time. The 113 culverts that made up these partial and full barriers restrict access to 302.8 km of aquatic habitat for various species attempting to move upstream to fulfill their life cycles.
With all of the data collected by the Broken Brooks project over the past three years, there is a great potential to further improve fish passage and increase habitat available to migrating and spawning fish of various species.”
– Theresa Johnston, Broken Brooks Project Leader
For access to the full scientific results of this project, download the 2014-2016 Broken Brooks Report.
What is a Culvert?
Culverts are the cement or corrugated metal pipes which you have probably seen under roads, driveways, and other forms of water crossings. Culverts are generally used for altering the path of a watercourse in favor of road or rail bed construction. They may be found in a multitude of designs and configurations, all with varying ability to maintain natural river processes.
Consequently, culverts can be improperly designed and/or installed, negatively impacting aquatic fauna (e.g. Atlantic salmon) that rely on continuous connectivity from marine to freshwater headwaters to complete their life cycles. Debris build-up, sedimentation, and large changes in stream height causing outflow drops are some examples of the barriers that poor culvert design can cause.
In 2014, The Petitcodiac Watershed Alliance (PWA) initiated the Broken Brooks project in the Petitcodiac River Watershed using the protocol designed by the Clean Annapolis River Project (CARP) and NSLC Adopt-A-Stream. The project was first initiated in 2007 by CARP in the Annapolis River Watershed.
The third year of the Broken Brooks project, which aims to assess the state of fish
passage through culverts, reaffirms the data collected from 2014 and 2015: the majority of
culverts installed on fish bearing streams in the Petitcodiac River are either partial barriers (23%) or full barriers (52%) to fish passage. This leaves only 37 of the 150 culverts assessed over the last three years as passable for aquatic species.The 440 crossings identified in the Petitcodiac River Watershed between 2014 and 2016 are divided into crossing type in the left pie chart. Culverts (total 150) given a detailed culvert assessment are further classified as either Full Barrier, Partial Barrier or Passable for fish migration in the pie chart on the right.
A single culvert blocking 500 m of upstream habitat to aquatic species may not appear to be detrimental in and of itself, but when you combine the 113 culverts that were evaluated as either partial or full barriers in our watershed, the total length of upstream habitat lost to migrating fish is just over 300 km.
A remediation option was selected for each partial or full barrier by consulting the British Columbia Ministry of Environment’s fish passage guidelines (2008) which recommended either the installation of an in-stream structure or, in cases of extreme culvert outflow drops and/or slopes, the complete removal of the structure.
From 2014-2016, 25 debris blockages were removed. Debris removals took place in the Pollett, Little, Weldon and North river basins. An accumulated 21 km of upstream habitat was gained by removing these debris blockages.
See a video of how we conduct Debris Removals here.
A rock weir, an in-stream structure that fortifies a stream’s existing tailwater control, was installed to eliminate an outflow drop from a culvert located within the Little River Basin. Combined together, these five remediation efforts restored fish passage to 25 km in length and 86 km² in area of upstream habitat.
Look at our Rock Weir video to better understand what that means!
The Broken Brooks team is proud to report that fish passage has been improved to just over 80 km of upstream habitat through select barrier culverts by installing rock weirs and removing debris blockages. But the job does not stop there, as there are still 36 partial or full barrier culverts that require research into implementing other restoration techniques.
Although the PWA will be able to remediate most barrier culverts by implementing in-stream structures, the Department of Transportation has been contacted, and the results of our Broken Brooks Project have been communicated to them. We hope with their newly acquired knowledge they will choose to manage and prioritize those culverts that require re-installation or complete replacement to facilitate fish passage.
If we can reach out and learn from our partners in aquatic restoration, the PWA has the potential to restore fish passage through 48 barrier culverts and increase the availability of aquatic habitat by another 174.8 km by using the data collected by the Broken Brooks Project. This high number of barriers, and the many kilometers cut off to migrating fish associated with it, indicates to fishermen, environmentalists and anyone who recognizes the importance of aquatic connectivity that the task of identifying and restoring barrier culverts in our watershed and beyond is just beginning.