A few years ago, I went to a workshop on erosion control, which gave me a number of tools to use against soil erosion.
One of them involves using logs and brush to make multiple leaky weirs, which slow water and sediment moving down a slope, allowing the silt to drop out instead of being carried all the way down to the river, as happens when there is not enough ground cover.
At that time, we didn’t have much spare brush, but in the meantime we’ve gained some dead wattles, lost branches from Dad’s many silver poplar trees, and had a few larger trees die in the garden.
That’s enough to start some erosion control.
I had my eye on the steep gully on the ridge behind our house.
Unlike some other gullies, I can’t fence it off and plant trees there because I’ve already fenced out the ridge beside it.
But I also don’t want to watch the soil turning into soup and dripping down the hill, as on the Adnamira side in February 2019
So I wanted to see if I could do something to control the washing out, despite the steepness.
Also, it would clean up the irritating stray brush and logs lying near the road where they are a fire risk. Those up on the hills do good service themselves as erosion control.
The idea is to start at the top of the area that’s washing out and work your way down, each layer contributing more.
We did do some barriers at the bottom as well, because it was accessible. Also, we dumped spare dirt excavated from the shed construction into the lower part, and fenced across it lower still, as part of an enclosure for one of our trees, which unfortunately was overturned by a freak wind.
So when my nephew David and his partner Nellie came to visit in April 2019 it seemed a perfect moment to haul a couple of trailer loads of logs around. Perfect for me, I mean.
With that help we were able to roll out the logs into a line roughly on the contour and peg them down with wire and short star pickets. Then bind brush and smaller branches on top to discourage sheep from jumping the barrier. One of the things that causes erosion is animal tracks that go straight up and down a hill. If you can get them to zig zag or mainly go across the slope, there will be less erosion. A lot of the time sheep do this because it’s easier anyway, but in this gully the water source is at the bottom and the most direct route is straight down the gully or the face of the hill.
Amusingly, I found when I looked on Google Earth that there we were, building the barrier. The erosion looks terrible at that time, and the barrier small and fragile.
A short time later we came back with Bush, one of the Congolese guys who worked for me in 2019. We extended the line right across that part of the gully, using logs from the poplar trees which regularly drop rather large branches. Luckily they’re not too heavy to lift, although some needed the Bobkitten to load with.
Once up on the hill, if they’re too heavy they can just be rolled out of the trailer and crowbarred down the hill until they reach the position you want. It’s important to build up the barrier enough to stop sheep jumping over, and they can jump pretty high. We also added some at the bottom of the hill, to start the sheep zigzagging away from the weakest points.
The results after the drought broke were encouraging – soil carried by the rain had banked up fully behind the flimsy barrier, retaining several tonnes of earth.
Unfortunately we also had to contend with the weeds that grew in it, and found that a wombat had tunnelled underneath to make a new hole.
To make the next line, lower than the first, we had to slash our way through the annoying saffron thistles. Patrick did a great job with that, and our neighbours from Benview helped with the dragging of limbs into position on a stinking hot summers day.
I’m still waiting for a good Google Earth photo of the improvements but I walked up the other day, carefully, among the thistles and rocks to see if I could get a better photo of the results. The sheep obligingly zig-zagged through the barriers. Okay, one jumped. But only one.