Advice with swales on my property

Hi guys, I've been thinking of putting some swales on a part of my property and would love to hear some thoughts. I've attached some photos.

I'm thinking over installing some swales on this section of hill, it's not a particularly large area and I imagine that I will dig them by hand. I'm thinking maybe three or four and having the tank overflow to them, as well as my kitchen and laundry grey water, perhaps after being filtered by a Reed bed or something similar. I also have a large pond/dam that the swales would over flow to, as seen in the pictures.

I live in Tasmania, Australia in a very wild section. I have a lot of kangaroos, Wallabies  and possums come through and graze the land, so was thinking of intially growing some native pioneering species that they will hopefully not pick on too much. I can grow some of these from seeds as I have 20acres of native bushland and have sourced some seeds. Was thinking of experimenting with other non native species also, to see how they go with the wildlife. If they become too large of an issue I may fence off the area, at least from the hopping animals (possums are much more difficult to keep out).

A concern I have though is my soil type. I have poorly draining clay soil, there are actually quite a few springs that pop up when there is a very heavy down pour and the water table has risen sufficiently, (which is naturally quite high). These quickly dry up though after a day of dry weather. There aren't any springs in the particular section I'd like to swale, but I have noticed in some sections the ground can make that squishy noise when walked on. This only persists a day or two after rain, and only after a few days of consecutive rain, after the ground is waterlogged. In summer though, things can get quite dry (we get majority of our rain in winter) and only have an annual average of 665mm (26inches). So I'd like to store that winter rain as long as possible in the landscape, I also rely completely on rainwater harvesting, so the less I need to water the better.

I have quite rocky soil and these rocks are quite large (have attached pictures). So I don't want to have the swales dug very large, to minimise the amount of rocks I'll have to sort through.

Anyway, just wondering if you guys have any thoughts? Does it sound like an okay idea? Is there another method that may suit better? I thought maybe a hugel type system on contour instead, as I have a lot work woody debris in the bush that I need to clear up a little for bushfire safety? Am also concerned about the slope of that land, not sure if it's too steep for swales. Thanks

That slope definitely looks shallow enough for swales. I believe the figure is less than 20% slope. Your property actually sounds like an ideal site for them. On clay, you want to emphasize swale depth more than width, and plant lots of trees from seed on and below the berms. This helps water penetrate more deeply. It sounds like swales with trees could help your springs run year-round. I don’t have to tell you how awesome that is. It sounds like your soil has low organic matter content. Try sowing buckwheat, daikon, and possibly more rampant plants like Japanese knotweed, giant knotweed and Jerusalem artichoke. Those plants are not for the faint of heart, though. They can really take over, depending on the soil and what deficiencies it may have.

Myron Platte wrote:That slope definitely looks shallow enough for swales. I believe the figure is less than 20% slope. Your property actually sounds like an ideal site for them. On clay, you want to emphasize swale depth more than width, and plant lots of trees from seed on and below the berms. This helps water penetrate more deeply. It sounds like swales with trees could help your springs run year-round. I don’t have to tell you how awesome that is. It sounds like your soil has low organic matter content. Try sowing buckwheat, daikon, and possibly more rampant plants like Japanese knotweed, giant knotweed and Jerusalem artichoke. Those plants are not for the faint of heart, though. They can really take over, depending on the soil and what deficiencies it may have.

Thanks for the advice, it would be great if I could get a spring to run all year round. Yes I need to look more into different types of initial cover crops like the ones you mentioned. I might actually measure our what the slope is because I'm not sure the photos accurately represent it. Cheers!

Joey Miller wrote:Hi guys, I've been thinking of putting some swales on a part of my property and would love to hear some thoughts. I've attached some photos.

I'm thinking over installing some swales on this section of hill, it's not a particularly large area and I imagine that I will dig them by hand. I'm thinking maybe three or four and having the tank overflow to them, as well as my kitchen and laundry grey water, perhaps after being filtered by a Reed bed or something similar. I also have a large pond/dam that the swales would over flow to, as seen in the pictures.

I live in Tasmania, Australia in a very wild section. I have a lot of kangaroos, Wallabies  and possums come through and graze the land, so was thinking of intially growing some native pioneering species that they will hopefully not pick on too much. I can grow some of these from seeds as I have 20acres of native bushland and have sourced some seeds. Was thinking of experimenting with other non native species also, to see how they go with the wildlife. If they become too large of an issue I may fence off the area, at least from the hopping animals (possums are much more difficult to keep out).

A concern I have though is my soil type. I have poorly draining clay soil, there are actually quite a few springs that pop up when there is a very heavy down pour and the water table has risen sufficiently, (which is naturally quite high). These quickly dry up though after a day of dry weather. There aren't any springs in the particular section I'd like to swale, but I have noticed in some sections the ground can make that squishy noise when walked on. This only persists a day or two after rain, and only after a few days of consecutive rain, after the ground is waterlogged. In summer though, things can get quite dry (we get majority of our rain in winter) and only have an annual average of 665mm (26inches). So I'd like to store that winter rain as long as possible in the landscape, I also rely completely on rainwater harvesting, so the less I need to water the better.

I have quite rocky soil and these rocks are quite large (have attached pictures). So I don't want to have the swales dug very large, to minimise the amount of rocks I'll have to sort through.

Anyway, just wondering if you guys have any thoughts? Does it sound like an okay idea? Is there another method that may suit better? I thought maybe a hugel type system on contour instead, as I have a lot work woody debris in the bush that I need to clear up a little for bushfire safety? Am also concerned about the slope of that land, not sure if it's too steep for swales. Thanks

Hi Joey and welcome to Permies!

First question I would ask is what are your goals for this section of property and why are you thinking of installing swales? It seems that different permaculturalists have different ideas about how swales are built and what their purpose is. I kind of follow the Bill Mollison/Geoff Lawton idea that swales are tree planting systems, and they need to be constructed dead level, with a good, sufficiently wide, undug spillway that empties out into a planned place where it won't cause erosion in an extreme rain event.

I see one of your ideas is to rehydrate the landscape, so swales + trees would be a natural for that. But of course, trees need to be protected from the roos and wallabies for a long time before they're potentially safe from them. So fencing might be where I'd start. (I live in a possum-free area so can't advise on them).

Re digging the trenches, with soil full of big rocks I'd be gagging for a small backhoe, but that's me. If you're gonna dig by hand, get some kick-ass tools, maybe something like the prong. You could use some of your rocks below your spillway to help prevent erosion. Or hell, reinforce something or build a gabion or a check dam somewhere.

I would not recommend trying hugel swales, as Jack Spirko says in this article. Go ahead and build hugels but do not make them into swales, I'd say.

Re your slope, I learned 18° as a maximum without calling out an engineer, especially on clay. Wet clay is pretty slippery. I really can't tell your slope from the pix, in the photo of the house it looks very steep, maybe over 20°, and on the more bucolic one it looks very gentle, more like 6°. Photos are very deceiving as you say. Maybe you can get an idea from Google Earth but that can be really inaccurate too. Does your state or local government have any contour maps available? 5 m contours would probably do to give you a general idea. Then with the distance on the map and the scale of the map and a friend who's good at trigonometry (or using an online tool like this one), you can calculate the degrees of slope. Of course then you need to use your noodle and on-the-ground knowledge to know when an area is a lot steeper than average and avoid swaling that up if the average slope is borderline.

Dave de Basque wrote:

Joey Miller wrote:Hi guys, I've been thinking of putting some swales on a part of my property and would love to hear some thoughts. I've attached some photos.

I'm thinking over installing some swales on this section of hill, it's not a particularly large area and I imagine that I will dig them by hand. I'm thinking maybe three or four and having the tank overflow to them, as well as my kitchen and laundry grey water, perhaps after being filtered by a Reed bed or something similar. I also have a large pond/dam that the swales would over flow to, as seen in the pictures.

I live in Tasmania, Australia in a very wild section. I have a lot of kangaroos, Wallabies  and possums come through and graze the land, so was thinking of intially growing some native pioneering species that they will hopefully not pick on too much. I can grow some of these from seeds as I have 20acres of native bushland and have sourced some seeds. Was thinking of experimenting with other non native species also, to see how they go with the wildlife. If they become too large of an issue I may fence off the area, at least from the hopping animals (possums are much more difficult to keep out).

A concern I have though is my soil type. I have poorly draining clay soil, there are actually quite a few springs that pop up when there is a very heavy down pour and the water table has risen sufficiently, (which is naturally quite high). These quickly dry up though after a day of dry weather. There aren't any springs in the particular section I'd like to swale, but I have noticed in some sections the ground can make that squishy noise when walked on. This only persists a day or two after rain, and only after a few days of consecutive rain, after the ground is waterlogged. In summer though, things can get quite dry (we get majority of our rain in winter) and only have an annual average of 665mm (26inches). So I'd like to store that winter rain as long as possible in the landscape, I also rely completely on rainwater harvesting, so the less I need to water the better.

I have quite rocky soil and these rocks are quite large (have attached pictures). So I don't want to have the swales dug very large, to minimise the amount of rocks I'll have to sort through.

Anyway, just wondering if you guys have any thoughts? Does it sound like an okay idea? Is there another method that may suit better? I thought maybe a hugel type system on contour instead, as I have a lot work woody debris in the bush that I need to clear up a little for bushfire safety? Am also concerned about the slope of that land, not sure if it's too steep for swales. Thanks

Hi Joey and welcome to Permies!

First question I would ask is what are your goals for this section of property and why are you thinking of installing swales? It seems that different permaculturalists have different ideas about how swales are built and what their purpose is. I kind of follow the Bill Mollison/Geoff Lawton idea that swales are tree planting systems, and they need to be constructed dead level, with a good, sufficiently wide, undug spillway that empties out into a planned place where it won't cause erosion in an extreme rain event.

I see one of your ideas is to rehydrate the landscape, so swales + trees would be a natural for that. But of course, trees need to be protected from the roos and wallabies for a long time before they're potentially safe from them. So fencing might be where I'd start. (I live in a possum-free area so can't advise on them).

Re digging the trenches, with soil full of big rocks I'd be gagging for a small backhoe, but that's me. If you're gonna dig by hand, get some kick-ass tools, maybe something like the prong. You could use some of your rocks below your spillway to help prevent erosion. Or hell, reinforce something or build a gabion or a check dam somewhere.

I would not recommend trying hugel swales, as Jack Spirko says in this article. Go ahead and build hugels but do not make them into swales, I'd say.

Re your slope, I learned 18° as a maximum without calling out an engineer, especially on clay. Wet clay is pretty slippery. I really can't tell your slope from the pix, in the photo of the house it looks very steep, maybe over 20°, and on the more bucolic one it looks very gentle, more like 6°. Photos are very deceiving as you say. Maybe you can get an idea from Google Earth but that can be really inaccurate too. Does your state or local government have any contour maps available? 5 m contours would probably do to give you a general idea. Then with the distance on the map and the scale of the map and a friend who's good at trigonometry (or using an online tool like this one), you can calculate the degrees of slope. Of course then you need to use your noodle and on-the-ground knowledge to know when an area is a lot steeper than average and avoid swaling that up if the average slope is borderline.

Thank you for the reply

Yes I am thinking a tree planting system and yes I agree that fencing initially would probably be the best way to got about this. We have planted trees elsewhere with guards, but they can still get nibbled at if there are any weak points. Possum free! Lucky you, I do think possums are great, but it would be nice sometimes if they played nice more often haha

Yes I don't think I'll he doing the hugel idea, but will be building a few hugel beds in the annual garden. Not the swale types though

I think the slope would certainly be steeper than 18° in sections. I'm actually now leaning on putting some swales in a different section, to the right of the house. It's a gentler slope and has a lot of run off from the French drain exit that runs behind the house. I'm thinking of putting in a small pond to catch some of that excess water and then putting some swales down hill for the overflow. After passing through some of the swales, it will make its way into the dam. The water at the moment eventually makes its way down to the dam (from the French drain exit), so I figure I can intercept it and get the water to work for me as much as possible.

But that leaves me to wonder what I can do for the section pictured.. might still consider a swale system, or perhaps just leaving it open. I don't want to fill that area too much as that is where the sun comes from (it's an East facing hill). Will keep thinking on it! Let me know if you have any suggestions. Thanks very much

Well, one of the massive advantages of swales is that you can take water right out on contour. Have you considered positioning the swale to catch the French drain runoff, and continuing the contour out to the east side? Maybe you can put a gray water system in on the east side, making a basin in the bottom of the swale partly filled with gravel planted to cattails and reeds for the gray water to drain into, and plant willows and cottonwoods and comfrey on the berm and downhill slope on the east part of the swale. That way, you can do a low pollard/high coppice system on the trees, and modulate the amount of sun to your garden, generating mulch and firewood at the same time. Reeds and comfrey are awesome mulch, and willow branches on the ground can also be.

Myron Platte wrote:Well, one of the massive advantages of swales is that you can take water right out on contour. Have you considered positioning the swale to catch the French drain runoff, and continuing the contour out to the east side? Maybe you can put a gray water system in on the east side, making a basin in the bottom of the swale partly filled with gravel planted to cattails and reeds for the gray water to drain into, and plant willows and cottonwoods and comfrey on the berm and downhill slope on the east part of the swale. That way, you can do a low pollard/high coppice system on the trees, and modulate the amount of sun to your garden, generating mulch and firewood at the same time. Reeds and comfrey are awesome mulch, and willow branches on the ground can also be.

Yes that's the plan, to catch the French drain run off with swales. There is quite a lot of water that comes out after a bit of rain. I'd like to catch it in a pond first, and then the overflow to go into the swales. Thanks!

Joey Miller wrote:
Yes I need to look more into different types of initial cover crops like the ones you mentioned.

I have been doing alot of research on cover crops and have 2 years experience so far (I know not alot) but anyway we just cleared a wooded area to turn into cover crop pasture for a soon to come berry orchard. Anyway going from woods to open ground, 1st year got weedy and had to Bush hog and mow alot once big stuff was killed. But that fall we broadcast seeded the whole area (2 acresish) with daikon radish, crimson clover, hairy vetch, and annual ryegrass. Those are all soil builders by the way. Anyway this spring was amazingly green and lush it was lovely compared to the way it was just a year and a half ago. All that stuff completely smothered all weeds this year, especially the hairy vetch it worked wonders on suppressing native weeds/grasses. We let it all go to seed and turn brown. By June-july it looked like we strawed the entire hill cuz it all died off due to heat. We then broadcast seeded buckwheat and sunflowers to get some cover for the rest of summer. They are still growing and going to seed. Which were letting all the cover crops we broadcast out go to seed so we continue the "covercrop" seed bank on site. So that's all that will grow back, in theory. I'll let you all know how it's all going next summer. But I highly suggest those cover crops for weed suppression and soil building, because they are all nitrogen fixers, and the radish bust the hard pan up for heavy clay soils. This fall after we Bush hog buckwheat and sunflowers and the few johnson grass stalks that popped threw, were gonna sling cereal rye(winter rye), radishes, alfalfa, and medium red clover. However I have been seeing some hairy vetch sprouting already so we know that will be onsite again this winter. And naturally seeded this time, YAY!!! I'll try to remember to keep everyone updated on how the cover crop onsite seed banking works out Haha.