Breaking hugel rules and making hugel swales WITH TREES!

There are so many good things about hugel mounds with respect to water retention and building fertility that I would lie to work them into my orchard (moving towards food forest) design.  Yes I have heard Paul's rant about hugel swales. I have noted that hugel mounds tend to subside over time.  

I have also seen wide swales alternating with trees, to provide a mowable swath for annual crops, in a slope that's not too great.  Was it Ben Falk or Mark Shepherd who was doing this? I saw it in a permaculture basics video series shot in the Northeast.

I'm designing an orchard/ food forest near Eugene Oregon. Rainfall is 47 inches a year but mostly in the winter. So it makes sense to try to trap enough rainfall to keep the ground moist all year. So I have taken to heart to slow, spread, sink, etc as all good permies will do. After steeping myself in the writings and rantings of many different permaculture luminaries I plan to accomplish this in the following manner:

On the southwest facing hillside I have in mind, the slope descends about 1 in 10.  With a 3 foot contour interval, the width is more or less 30 feet between contours. I would like to remove topsoil and shape the hillside into flat terraces with a berm on the outer edge two feet high on the uphill side, flat for 3 feet, and going down 5 feet on the downhill side at about 45 degrees.  After the topsoil is replaced, the slopes are to be sowed with clover and other good ground cover, and planted with various berries, filberts, and annual guild plants.  This leaves about 20 feet for a mowable fertility crop or pastured chickens or other adventures. I have enough slope for about 5 or 6 terraces 50 feet long.

On the top of the berm I want to plant fruit trees of various kinds. Because I don't want these trees riding the slow avalanche as a hugel mound slowly collapses on itself, I am thinking of cladding the slopes of the berm (made from subsoil) with another 6-10 inches of logs and broken up ramial branches my predecessor has left lying around, then placing the topsoil on top of that, seeding with green mulch, and planting bare root fruit trees into the center of the berm and shrubs etc on the long slope. See the sketch.  

I am ignoring recommendations about hugel mounds going across contours, not mixing hugels with swales, and I don't know how many other no doubt well considered points of general advice given by people smarter than me.  My reasons are (1) frost and cold air flow is not a huge problem in Eugene (2) water must be controlled in both wet and dry seasons (3) I want to make use of all the red alder and douglas fir logs already cut and stacked hither and thither on the ground, some no doubt beginning to rot, along with some gnarly brush piles, and  (4) I want to play free-range bacci ball, graze chickens, and grow annual crops on the mostly flat terraces between the trees.

So what problems do you see in this approach?  I'm one of those guys who has read a lot but have never taken on a project like this, so I'm bound to have some blind spots. Advice appreciated.

I have also posted this topic to the Regenerative Agriculture forum on Facebook, where I got some good suggestions, my thanks to Silas Bennett:

1. slope the lanes slightly down toward the uphill side to direct the water away from the berm in ordinary rain events
2. provide spillways armored with a rock apron for extraordinary events
3. build the hugel mound alongside the downslope and above the grade of the lane below, where settling will not create problems.  The foot of the downslope being where the rainfall on the lane will collect in ordinary events.

other comments still welcome.

FWIW we've done one fairly large hugel 1.5m high by about 50m long that is NOT on contour and its water retention is excellent. Its working quite nicely and that is despite having a decent cover crop on it (we did it at the wrong time of the year). We're veruy happy with it nevertheless.

I'd heed advice not to use them on contour, if the hugels are going to be large. Sepp doesn't do this for a reason.

We're going to terrace our entire place and where possible break those terraces up with large hugels running down hill (well, not on contour). We'll capture water with channels/drains that will run into a series of ponds/dams, but we're hopeful that the hugels on the terraces will sponge enough water to increase overall water storage IN soil.

We're on top of a large hill, so dont have frost issues, we want to keep it that way and I am a bit wary about swales.....I guess we'll see how they go/behave....but I am more in favour of terraces only at this point.

I meant to ask - which way does the wind blow? is that an issue?

Wind is a problem for us as in its a problem for flowering fruit trees. I'd have a think about how you're going to manage that if the fruit trees are on top of the riser like you have in your drawing

I have to say that as escrow has not closed I am exiled to San Diego, 1000 miles away, until January.  I am going on my notes about the property taken at my inspection in October, trying to form a plan that will have to pass scrutiny after I can make more detailed observations.  The highest monthly winter rainfall averages are 6.8 and 7.4 inches for the months of Jan- Feb and it cycles to less than an inch in Jul-Aug.

The hillside in question is a clearing about 150 feet up from a seasonal creek, with plenty of forested land on all sides with Douglas fir of 40-50 feet tall.  The top of this hill is off the property and at least 3-4 times that high.

I have not observed the property in all seasons yet, though I have rainfall records and other data logged about 3 miles away.  There was 1.65 inches of rain on the heaviest rain day last year. Strong winds and deluge style rain doesn't seem to be the norm here. The surrounding well-treed areas seem to shelter the area from strong winds. The local airport has wind speeds that average about 10 mph, rarely as high as 20mph and generally the wind is uphill, from the South. That's without the sheltering from the trees.

I want to understand your concern with fruit trees on berms, and wind.  Please spell it out for me.  Here are some other details that might help.

I plan to plant only enough trees of the same type for fertilization, and they would be adjacent to their pollinator companions, though widely spaced, with non-fruit trees distributed throughout. The emphasis being to grow as many different fruits as possible. Beekeeping is part of the plan, as are plants to attract wild pollinators.

You should be ok with the wind then....we get 100km/h so that's an issue.

Fruit trees / flower buds (fruit) / wind isn't an easy mix to deal with, hence in cases with wind, you want a large amount of protection

From your drawing and description, I would say that you are not building hugel swales.  What you are doing, is making swales using mounds above grade, that have wood near the surface on the downhill slope.  This is quite different.  

To start with, making swales with mounds above grade is not highly recommended... in fact it's not recommended at all.  I'm guessing you know that from your studies, but you might not know why that is.  And I have to assume that at this point, and proceed to explain.  A swale is a ditch on contour.  A swale uses the stability of the soil on grade down-slope to hold the water.  The down slope mound never holds the water.  A swale built above grade as you are planning is not a ditch on contour, it is a mound that is expected to hold water as if it was a ditch on contour, and a mound is, by nature, a great deal less stable than a plane of grade material.  That is the problem.  By saturating this mound, you create instability, not only down-slope, but also for your trees (more about the trees later).

The primary issue with hugel swales is that the woody material that is encased in the center of the berm which is above grade will saturate, holding a massive amount of water and thus weight, potentially sending all downhill in a slump, slurry, or landslide.  This could especially be compounded by having trees on it, which would be stabilizing... to a point... and then, quite catastrophically... not.  But since you are basically building raised beds, with some logs below the surface on the downhill side, then you are not really making the same situation... or not quite...  It could still be bad, since your swale is not cut below grade, and because it still has some logs in it and they are not below grade, so this might have a similar effect, particularly in a large rain event, but it will probably not create nearly the same effect as a bunch of soaking wet rotten wood, fungi, and soil, with no swale or spillways, which is what I thought when I read your subject line in the first place.  Not nearly the same effect as true hugels built as swales, but still potentially quite bad.  Then comes Silas, thankfully.  

1. slope the lanes slightly down toward the uphill side to direct the water away from the berm in ordinary rain events

 This seems to be telling you to make an actual small swale up-slope of your mound so that your mound is not seriously taking water against it... at all.  That's a really good idea.

2. provide spillways armored with a rock apron for extraordinary events

 You have to have a clear understanding of what this means.  True swale works and spillways are going to save your project, no matter what other choices you make.  You have to provide multiple gaps in your mounds across each contour of your slope to allow heavy rain events to fill your swale and then pass to the next swale down slope.

I'm not sure I understand Silas's wording on this third point.  So I'm not going to comment further on it, and will treat it like it isn't here until I see it clarified... especially in a way that shows what you think it means, so that I understand what your plan is regarding it.

So it makes sense to try to trap enough rainfall to keep the ground moist all year. So I have taken to heart to slow, spread, sink, etc as all good permies will do.

 Yes, this makes perfect permacultural sense, but a traditional hugulkultur does this without the potential hazards, if it's built off contour.  Your winter moisture will be preserved within the mounds and a lens of water will be extended in all directions but particularly downhill from the mound, regardless of whether you have it on contour or not.  Yes, you will trap more water if you do it on the contour, but it may not be quite how you imagine it, if you don't design it right.  For instance, my own raised beds are great because I can plant my garden right away after the snow melts when others in my area are waiting to get into their gardens because the garden is too wet in the spring.  This might be the case for the area near your hugul swales... too wet to really work on or do things in the early spring.  If you build real swales and proper spillways, then you should alleviate many of the problems.

Beyond all of this, above, and even though I can tell you really want to break all the rules, I still have to say this: Trees should not be planted on mounds that you create, regardless of whether they are hugulkulturs, or not.  Shrubs maybe, but not trees.  The mound is considerably less stable than soil in the ground, and trees thrive on stability (period->. or as the Brit's say... Full Stop).  Swales and hugels can be tree planting systems, but they are not done the way you are doing them, and this is mostly because it is simply not optimum for stability.  Your trees will thank you if they are planted down-slope of the mounds, not on the mounds, not on the down slope of the mounds, but instead of all that... just completely and fully down slope of the mounds.  They don't have to be far from the mounds, just not on them... at all.  They will thrive by putting feeder and water gathering roots into your mounds (hugels or raised earthen berms) finding all the water and extra nutrients they need if the down slope lens is not sufficiently providing.  You can still play bacci, graze chooks, and grow veg on the terraces between your swales and mounds, and your trees are in a stable location, and they help to stabilize your mounds.  

So what I would do?  What advice would I give you.  Build traditonal hugulkultur and do it on the contour! What?  Did you read what I just wrote? Yes, build em on the contours... But [ And this is a big   B~U~T ] do only small hugulkulturs, and put all the wood below grade with soil above, and in between them put proper spillways, draining the overflow of true swales using the dug out material from these swales to put on the hugul wood, and down slope of the mounds plant your trees.  That is my advice.  You can have all of your plans work with that, and you gain all of the benefits of the systems as they have been proven to work.

Please, Please.,,, Read this, and watch the video that goes with it too.  It'll be worth it.  Jack Spirko explains  

A quick thank you to Roberto and Peter for taking an interest and sharing their concerns.  Their posts require and deserve some study and so I will do that over the course of my Thanksgiving family-intensive holiday.  See you on the other side.

I unnecessarily raised the hackles of some folks thanks to my incendiary headlining.  Nonetheless I have watched and read the material and have concluded that 1) there are ways to do this without collecting a lot of surface water in the slope and 2) I might as well wait until early January when I will be in residence before detailing my system, so I can measure particular slopes, etc.

1) there are ways to do this without collecting a lot of surface water in the slope and 2) I might as well wait until early January when I will be in residence before detailing my system, so I can measure particular slopes, etc.

 Good call.  My advice: Walk the site, and envision various ideas that you have as already existing.  Walk the path of the water as you envision it to flow on the slope, through the various structures that you are conceiving and through the living things, as it proceeds downhill, and downwards in the Earth, and back into the sky.  Just FYI: Any slope greater than 25 % is too steep to build swales and is best forested for natural/indigenous regeneration, rather than production/economics.

Hal, I hope you don't mind me asking this question on your thread....but Robert has just partly answered a question I recently posted on another thread about soil depth, mounds and tree planting. I'm hoping you might elaborate Robert! Either in this thread or in my original here:

https://permies.com/t/60838/advice-improving-wet-conifer-woods    (There are pictures of my woods on that thread if you scroll down.)

Robert, you mentioned never to plant trees on a mound that's been created.

I have a 70% black spruce, boreal-type forest, with patches of birch and occasional maples and small alder brush throughout. Labrador tea and cinnamon ferns are the main understory with lots of moss as the main ground cover. (~60" rain/yr, zone 6 a/b, a km from the Atlantic,)

We've been opening up these woods with roads and paths for another project and I was hoping to plant food and medicinal guilds on the newly opened up edges. However....

There's very little soil depth - it ranges from < 6" in the low spots to about 2-3 ft in the high spots - most of which are made up of dead-fall - essentially old hugels, which the spruce like just fine. Or else there's a granite boulder under them! The lowest spots are water-filled for much of the spring, fall and winter, drying almost completely in summer. There's no slope at all across this landscape, it's more like a bowl. And the base of the bowl is mainly shale. Where there is soil, it's sandy clay and in the boggiest spots, it's peat.

I had been looking at enlarging and possibly increasing the height of existing mounds for planting small-ish fruit trees and shrubs. Is this feasible?

I will need to raise them above the soggy bottom of the low areas so their feet aren't wet. I had been guided to think about keeping them 2-4 feet above the water table. In this forest, 4 feet is way higher than I can go, but 2 ft is doable.

I certainly understand what you're saying about the mounds being unstable for trees. So am I better off to fill a low spot with good heavy soil for anchoring roots and then raise it just slightly above the surrounding grade to bring the tree's crown further up and away from the water?

Or rather than thinking of a "mound" for trees, should I be looking at raising a larger area that will become more stable over time?

What I have to work with right now is the heavy clay and shale mix that we're building roads with (it is proving very stable and well draining for the roads) and also an enormous amount of softwood chips created during the road clearing. I'm also willing to wait a couple of years while things settle and decompose.

Any advice would be greatly appreciated!!

Susanna, I will post on your other thread.

Robert, I’m a little mystified as to your statement about planting trees on swale mounds. That is accepted permaculture practice and is used successfully by many, including Geoff Lawton. I have never heard the claims you make about instability before. Perhaps there are soils in which planting trees on the mound could be problematic, but I am incredulous that it is almost universal.