FAQ’s
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Fresh Water Species- Identification Sheet
What is a digger log?
Example of a digger log structure built by ISAA.
The log is usually harvested on site with landowner permission, and the rock is retrieved from the substrate of the river. The log is placed on a 30-degree angle and on a 3-5cm/meter slope. The log is placed on an angle so it can direct the water flow which creates that meandering pattern over time. The slope is used to direct the water flow to one side of the log which is what helps to create those pools. The logs are dug into place and are secured with rebar using hand tools only. On the upstream side of the log we build a ramp with rock and sand materials which plugs up the water and forces it to flow overtop the log. The ramp also creates spawning habitat for trout and salmon! Each season we provide general maintenance to our previously installed structures. The digger logs usually only need rock and sand added, but sometimes require a replacement.
A digger log is a common structure that ISAA installs in a stream during habitat restoration. They are used to define meandering patterns in a stream, while also creating spawning habitat and pools for fish population.
What is a deflector?
Example of a deflector built by ISAA. This one is one of the largest deflector structures we have built. It is measured 6x3 meters and is two tiered.
A deflector is a common structure that ISAA installs during a season of habitat restoration. It is typically a 30x90x60 degree triangle shaped structure that is built on alternate sides of a river. The outside frame of the deflector is typically built with softwood logs and is secured into place with rebar. The frame is then filled in with rock, tapering up into the riverbank. The size of a deflector depends on the characteristics of the river, but all deflectors achieve the same end goal which is direct water flow to narrow and deepen the channel. They also dig out pools and create meandering patterns which helps to control sediment deposits. Overall, they are efficient and are easy to build by hand. If materials are not located around the work site, the cost can be high for materials to be bought and transported in. They also require annual maintenance which is done by ISAA during the first 6 weeks of the season.
What is a rock sill?
A rock sill is another structure that is installed during habitat restoration and is very similar to a digger log as they provide the same results. Usually ISAA will install a rock sill in an area where bedrock is located or in larger rivers where a digger is not suitable in size. They are placed on a 30-degree angle and are around 30cm high. The rock is placed in a linear direction across the river, and a ramp is built on the upstream side of the structure to help direct waterflow. The 30-degree angle helps direct the water flow which creates a meandering pattern and deep pools for fish population. Rock sills can also be placed straight across a river to backflow water in areas such as a culvert to create fish passage. These rock sills are higher than usual depending on the results that you are trying to achieve. Most times, rock sills are very effective but can require lots of maintenance or a full rebuilt the following year due to winter damage.
Example of a rock sill placed on a 30-degree angle, similar to a digger log structure.
Example of two rock sills placed straight across a river to backflow
water, allowing fish to migrate past the culvert.
What is a channel blocker?
A channel blocker is used in areas of erosion or flooding. They are built with stacked logs and are secured with wooden braces, spikes, and rebar. Behind the channel blocker we like to place rock or brush to stabilize the structure more, and to prevent water from flowing past it. Channel blockers can help deflect water flow, narrow out channels and stabilize banks by preventing further erosion. They are easy to build by hand and require very little maintenance.
What is a fish ladder?
A fish ladder is a structure that is used to help fish migrate past an obstacle such as a culvert. There are several different designs for a fish ladder, but all achieve the same results which is to create fish passage. ISAA had gotten one installed in the past with the NSLC Adopt-A-Stream on the More Brook. The ladder that we installed was made from a fibre glass tub and has metal shoots so the fish can swim up and down the river. Inside the culvert we installed wooden baffles to build up the water depths to make fish passage easier. Each year during winter damage assessments and maintenance we clear out the debris and built up rock materials that are inside the tub. Overall the fish ladder has been very successful and efficient!
What areas do you work out of?
We work out of Southern Inverness Country on several watercourses within three different watersheds, see table below.
