Amphibian Friendly Layers Added to Bridge Pathway

Creating an amphibian-friendly pathway over the rip rap beneath the Lost Shoe Bridge has continued since our earlier post this summer. We had always planned to add soil and plants over the mixture of sand and small stones, called "pit run", used to fill cracks in the rip rap. The importance of doing so was reinforced when we watched a Wandering Salamander struggle to get purchase on the "pit run" as it climbed up the slope at one of the bridge corners. 

Adding organic soil was a good idea, not only to provide a surface easier for salamander feet (and frog feet) to grip, but also to help hold moisture on the path that we want these moisture-loving creatures to cross. 

Once the summer heat subsided and rain began to fall more regularly, it was time to add native plants. We placed a layer of organic soil over top of the pit run and secured more pieces of downed wood to the rocks under the bridge. 

Then, from the corners where the fencing meets the bridge abutments to as far as the light can reach beneath the bridge, we planted dozens of sword ferns and lady ferns, sedges, rushes, false lily of the valley, coastal strawberry, twinflower and mosses. The final step was to spread fallen alder leaves over the soil and around the plants.

The following photos show the transformation from rip rap to pit run to a vegetated path in the southeast corner of the bridge.

More dramatic results happened in the southwest corner where the log placement reduced a steep drop across the rocks where the amphibian fencing joined the bridge abutment.

We were very pleased to find a Rough-skinned Newt on the path at this corner last week. It camouflaged well with the layer of dead alder leaves.

Our ongoing task is to monitor amphibian movements beneath the bridge. We installed cameras and search for frogs and salamanders along the highway and fences during warm rainy nights. The survey data will give us a relative measure of how many amphibians are moving across the road and being intercepted by the fencing. This will provide an index of how many we should expect to photograph moving under the bridge if our path is working!

Stay tuned for the results later this winter after we go through our camera images!

The Central Westcoast Forest Society, B.C. Ministry of Transportation and Infrastructure and Habitat Conservation Trust Foundation support this project. We are grateful to them and a dozen community volunteers who have helped with the night surveys.

Guidelines for Amphibian & Reptile Conservation During Road Building & Management Activities in British Columbia

The provincial government has produced a set of guidelines at their website for reducing the impacts of roads on amphibians and reptiles in British Columbia. It's a resource for environmental consultants and various levels of government, industry and private landowners who build, manage and maintain roads in our province. It is a "living document" that will be updated as new information becomes available. We're happy that some of our work was included in the current version and we're onside to share more as we explore ways to improve passage for frogs and salamanders under Highway 4 on the west coast of Vancouver Island.  

Watch this video to see why amphibians and reptiles in BC need our help when it comes to roads.

Creating a Path for Amphibians Over "Rip Rap" Armouring a Bridge

Summer 2020 is an eventful year for improving amphibian passage beneath Highway 4 on the west coast of Vancouver Island!

Parks Canada is installing three new box culverts close to the one we put in place with the BC Ministry of Transportation and Infrastructure in 2011. We're looking forward to sharing the design features of the Park culverts and fencing system once they are complete in a few weeks.

In the meantime, we have shifted our attention down the road to another crossing structure, a bridge over a tributary to Lost Shoe Creek. The bridge allows passage for Coho Salmon and Cutthroat Trout, as well as four-legged wildlife that can swim in the current or hop along the exposed shoreline. It's easy to move under the bridge at low water levels in summer but not during the rainy season. When water rises, flow increases and the shorelines become gnarly. The banks of the creek are armoured with large sharp angular rock, known as "rip rap". It protects the bridge abutments from scouring by heavy water flows. This is standard practice for bridge construction in British Columbia and other places, but it creates impediments to passage for smaller creatures like amphibians. They can get stuck in the cracks between the angular rocks! 

This particular bridge occurs at a hotspot for migrating Northern Red-legged Frogs. Several of their breeding ponds and forested habitats occur on opposite sides of the highway near Lost Shoe Creek. One of the habitats is an artificial salmon-rearing off-channel constructed in 2013. In 2014, we installed ~ 200 m of fencing to stop frogs and salamanders from being killed on the highway near the off-channel. Although the fencing works well to reduce the number killed, it blocks passage between habitats. 

That's where the bridge comes in... it could be the perfect habitat connector if we did something about the "rip rap". So that's what we're doing. Working with a crew of stream habitat restoration specialists from the Central Westcoast Forest Society, we spent the last two days creating a smoother path over the "rip rap" under the bridge. 

Our pictures tell the story:

Step 1. The crew reviewed how the amphibian fencing connects to the bridge abutments.

We explained the problem with the "rip rap", and our objective to create better pathways for amphibians under the bridge.

Step 2. We received a truckload of "pit run", a mix of coarse sand and rounded gravels from a local quarry. The truck delivered a quarter of the load to each corner of the bridge.

Step 3. The crew shovelled the "pit run" into wheel barrows and buckets so it could be carried under the bridge.

To prevent disturbance and ensure we didn't spill dirt into the stream, we did all the work by hand.

Many buckets and shovels full of dirt were transferred...

... to where it was placed to cover the "rip rap" bench above the high water line.

We raked to create a smooth pathway...

... then added more buckets to fill in gaps.

At one point we noticed a Northern Red-legged Frog sitting on a rock in the creek!  It seemed to be watching our progress. To see the frog check out the closest rock to the camera in the foreground.

Step 4. We measured the length of logs needed to place across each slope at the corners of the bridge.

We cut the logs...

... moved them to the bridge corners...

... and positioned them where they will help lessen the steepness of the approach from the ends of the fencing.

Step 5. To secure the logs, we drilled holes in the rocks, washed out the rock dust, and then inserted glue for cable.

After securing the cable in the rock holes we cinched it around the logs with staples.

Then covered the logs with landscaping cloth and poured more buckets of "pit run" on top.

We smoothed the surface to create a shallow slope from the ends of the fences around the bridge abutments.

Some of the fences were overgrown by alder trees so the crew used a powerful weed wacker...

... and cut back the alder to make a clear path for the amphibians to follow to the bridge.

We needed one more bucket of dirt to fill a steep section along one of the fences.

It felt good to deliver the last bucket!

The crew will take a break from this project for several weeks until it's time to plant. Then we'll use wildlife cameras to monitor the frogs and salamanders that move along the new paths and compare to what we saw moving over the "rip rap" last year.

We are grateful to the Habitat Conservation Trust Foundation and the BC Ministry of Transportation and Infrastructure for funding this work. 

We hope information that we share about the effectiveness of this project can help create smoother passageways for amphibians in other places!

What Have We Been Up To ...

Our projects to mitigate the effects of roads on amphibians on the west coast of Vancouver Island are still underway. We invite you to read about our recent work in our annual newsletter - the SPLAT UPDATE for 2019-2020.