Sunday, August 24, 2008

Digger Logs

Yesterday morning at 9 , 4 of us from the Sackville Rivers Association went to a spot on the Little Sackville River to do maintenance on a digger log. Digger logs are installed at several points on a river for a number of reasons. I've explained before about how we're trying to restore the natural meandering of the river. Installing the logs allows us to divert the flow of the river ever so slightly. It is placed at an angle, opposite to the one before it. In the first picture, looking upstream, the water will be mostly coming to the right of the log (on the left of the picture).So now we have to place deflector rocks on the upstream side of the log and dig out the rocks and stuff from the downstream side of the log. Deflector rocks help hold down the log and deflect ice off it. As chunks of ice move down river, they should slide right over the rocks rather than into the log. They also help deflect some flow of the river. Removing rocks and stuff from the downstream side of the logs creates a pool for the fish to rest as they move upstream.

This particular rock that I dug out is all sharp and raggedy. It's not a natural river rock, which would be smooth with rounded edges. It came directly from a quarry and ended up in the river either during construction in the neighbourhood or someone brought it in. More likely the former. There's a tiny white spot on the rock that reveals a vein of quartz. Whether a rock is smooth or not we'll use it.

So after shovelling two tons of rock and debris from the river, I sat down in the middle and just hand picked the rocks, throwing them to the appropriate areas. Behind me you can see a line of rocks that define the downstream side of the pool. You can also see my bug net in the background just in case I came across something interesting.
Another picture looking upstream. On the right side of the picture you can see how we built up the rocks a little bit. On the left side of the picture you can see where the water is flowing more quickly over the log. The quicker flowing water will churn up the bottom of the pool and help make it a little deeper plus it will help oxygenate the water. We placed rocks at the downstream side of the pool to help define it and to also concentrate the flow of water. We also started to fashion a trench to the bottom of the pool.
In the last picture you can see the "gurgling" water flowing over the log. On the right you can see a lone rock. We dug out a little bit of debris from around this rock located in the middle of the pool. That's to offer some protection to the fish as there isn't really a place to hide from predators in the pool.
We're not done yet. But the basic structure is there. Our fearless leader, Walter, said that if you remove the rocks from a river you remove the singing of the water. Or something like that. It was rather profound, for Walter. Anyway, we're just rearranging them to make the water sing a little louder.


As always, click on the pictures to get a closer look.