Brisbane Local Food
It's the rainy season here in Australia, so I decided to put in some proper swales.
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Cheers Cres. I did get the vetiver planted all around the bottom end. It's been so dry though that it really hasn't gotten going properly yet. I hadn't thought about a proper overflow but yeah, I'll need to put one in.
Andrew : Your water retention setup looks good. In one of my newly built swales I hadn't completed my overflow and the following day a downpour broke the berm (A backyard is small scale so wasn't a major flooding issue) but it reinforced what I'd learned and seen implemented on dams and swales on a much larger scale (50tonne excavator style!) on my friend's permaculture farm.A recommendation for your overflow channel. Either put a lot of rocks/old pavers in and around it or something like an overflow pipe. I use a short bit of 90mm stormwater pipe and cover with rocks and dirt, as well as pavers and rocks on others. What happens in a massive downpour is that the narrow egress point erodes very quickly both downwards and sideways as the water velocity increases through the narrow gap.Dave touched on vetiver to stabilise the banks which is a great idea. I plan on planting vetiver on the berm, the deep roots will hold it together, access the swale water but keep the swale free for maintenance. I still think you ideally need a 'non erodable' type exit point.Personally I put the exit point on the end of the swale that's on higher ground. Given the swale is obviously on contour it is the end where the height of the berm is shortest. It maximises the time water is spent on my land.I put wood chip and prunings in my swales. Some washes away but mostly it soaks up water and keeps the swale wet for much longer allowing the water to seep deeper into what would normally be hard clay. It also means I can go a little bit deeper with the dig and still walk across the channel without rolling my ankle.
They certainly slow down the water which is what I wanted. Of course, we've had so little rain that I can't really say if it will have an impact on the plants.
How did you go with these a few months on? Happy with them? Do you think they are working?
I put some pretty substantial rocks on the corners where the water would undermine banks. I'm not so worried about banks. My biggest worry is that I'm worried a big downpour will move the mulch. I'm wondering if I could plant a few vetiver inside the swales to slow the flow. I could also then use it to increase the height of the banks and maybe chuck a few more big rocks into the low points.
True -- Christa is right: Vetiver is a good option --and you'll save on your sugarcane mulch bill as you'd have a domestic harvest of mulch.
'Swale' is very much a Permaculture term that presumes physical digging and heaping. Whereas Vetiver 'grows' a swale if you lay it out according to your contour preferences -- your sculpting to a plan.
Watching the video you'd have two options, I reckon:
I'm not qualified to 'consult' on bio-enginneering challenges -- but yours is a small scale problem that a few plants -- later divided into greater numbers -- could readily solve.
Christa's drainage problem --that she applied Vetiver to -- seems similar to yours.
My guess is that many rising blocks on smallish lots in the Brisbane foothills could utilize Vetiver plantings for drainage management...with the added advantage of a ready mulch harvest.
And Vetiver, as grasses go, looks good.
Have you thought about using some vetiver around the edges to hold the banks of soil. It looks much better than the last time we saw it, Andrew.
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