Improving Steep Wet Clay

Hi Everyone, long time lurker, first time poster.  I have done a lot of reading trying to figure out the best solution and feel like I'm spinning in circles at this point, so I'm looking for some expertise from this awesome community!

I lived on the north face of a mountain in the southeast US, zone 6.  There is a space behind our house that is fairly seep 20-30% slope, soil is pretty heavy clay and it stays wet and mucky for most of the year, and I am looking for ways to imrpove it for both growing/and the ability to walk on it.  Long term I would like this to be an Orchard/food forest area.

We get pretty consistent rain throughout the year (2-5" a month), and the slope stays consistently wet and mucky for most of the year, except for in the heat of summer.  

What would you do with this to build soil/and help it stay more dry?  I have let it go to prairie for the last 2 years (previous owners kept it tightly mowed), that has helped a bit, but I'm looking to accelerate the process.  The area is fairly big (75 yards by 20 yards) and I don't have access to big equipment due to driveway difficulties and retaining walls I can't get anything sizeable there to do large scale earth moving, so solution that require earth moving will have to be done with a shovel.

Picture attached for some perspective on the space.

certain things grow well in such conditions, it might be more efficient to plant what will enjoy those conditions rather than try to change the nature of the soil or slope. for example ginseng only grows on north facing slopes.

Tyler,

Welcome to Permies!

Tough challenges!  I can think of two things that you could possibly do to help.  The first, as already mentioned, is to get some good, deep rooting cover crops growing.  This will help to improve/build soil and will help with the mud.

Secondly, is it possible that you could divert some of the water that flows across the land?  Even if you could adjust drainage a little bit, you might be able to save yourself some goopy, sloppy conditions.

Eric

Alder could work. It grows fast and loves water and clay.
We have an alder forest here on varying slopes from 0 to 100%. The forest floor is generally good to walk on unless it is a very steep slope or animals or humans have exposed the clay below it…

Eric Hanson wrote:Tyler,

Welcome to Permies!

Tough challenges!  I can think of two things that you could possibly do to help.  The first, as already mentioned, is to get some good, deep rooting cover crops growing.  This will help to improve/build soil and will help with the mud.

Secondly, is it possible that you could divert some of the water that flows across the land?  Even if you could adjust drainage a little bit, you might be able to save yourself some goopy, sloppy conditions.

Eric

Thanks Eric!  I have some winter rye cover crop on it now, think I'll start resrearching what to follow that up with.  Its also a challenge because the wetest spot is a natural walkway (flat spot at the bottom of the slope).  I think maybe water diversion just before that might make sense.  Would a swale off contour be a good fit there?  Or do you think something more traditional like a french drain since it runs right behind (and uphill) relative to the house.

Sebastian Köln wrote:Alder could work. It grows fast and loves water and clay.
We have an alder forest here on varying slopes from 0 to 100%. The forest floor is generally good to walk on unless it is a very steep slope or animals or humans have exposed the clay below it…

Thank you, I'll look into this!

Tyler,

I was actually thinking about some type of swale, even if just a short one.

Eric

And by short I meant vertically short, like maybe 6” tall would be enough.

Eric

Eric Hanson wrote:Tyler,

I was actually thinking about some type of swale, even if just a short one.

Eric

This makes sense. I had kind of ruled out swales because of the steepness, but I think one right at the bottom before the foot traffic area may help.

Thanks!

I'm on the north slope of clay hill, too. Our house caught sheets of run off during heavy rain events. We cleared the overgrowth behind our house and did have the opportunity for some heavier equipment, so we put in swale/hugels:  the largest trunks of some of big sweetgums were laid out almost on contour (but with a clear drainage to away from the house) and dirt from the uphill side was scooped and dumped on the logs. We had many many logs and no need to burn them. Using the logs as sponges and the swales to redirect has made a huge difference, especially during some historically wet seasons. Getting something to check and redirect runoff might help you.

Judielaine Bush wrote:I'm on the north slope of clay hill, too. Our house caught sheets of run off during heavy rain events. We cleared the overgrowth behind our house and did have the opportunity for some heavier equipment, so we put in swale/hugels:  the largest trunks of some of big sweetgums were laid out almost on contour (but with a clear drainage to away from the house) and dirt from the uphill side was scooped and dumped on the logs. We had many many logs and no need to burn them. Using the logs as sponges and the swales to redirect has made a huge difference, especially during some historically wet seasons. Getting something to check and redirect runoff might help you.

Hmm I have some pine trees upslope of this area that I was contemplating clearing out to let more winter light through to our solar panels, but I didn't know what I'd do with them once they were felled, this might be perfect for those.

Hi Tyler,  Welcome to Permies.  

Your clay slopes and high water situation are not ideal for hugulkulture.

If you do decide to put huguls on the slope at all, then do not put them on contour as a swale.  Make sure they are off contour, like maybe even diagonal as your slope is quite steep, and already holding plenty of water.  You could get away with having them go up and down the slope with no harm, if you wished.  You could put one down near the bottom, across the slope and slightly off contour, to absorb water at the path spot you mentioned.  The risk on the slope is waterlogging the hugul material above grade and it failing catastrophically in a large rain event if it is put like a swale, directly across slope, and is holding water.  

Swales and huguls are not mutually inclusive, and were never meant to be built together.  Generally swales are in slopes that are less steep than your property.  Generally huguls are not put where there is already adequate moisture.  Clay is a slow moving form, downhill, when it is saturated.  I wouldn't recommend adding more weight to that, especially above grade, and since you don't have a machine, it's unlikely that you'll be burying it deep enough to alleviate that problem.  

That all said, your plans to put in an orchard is actually a really great idea!  Slopes of that degree are meant to have trees on them for stability.  Swales are tree growing systems, but in your case, divergent drains (basically a swale shape, but off contour slightly so it drains some of the water, might be workable/desireable.  I'm not sure the species that you have in mind for your orchard.  Alder was mentioned, but it might not be the best for your zone and region.  What alder does do, and what you might want to look for in qualities from a tree from your area, is grow fast and fix nitrogen, while stabilizing the slope with it's roots.  The sooner you get trees on your slope, the more stable it becomes, and the drier it can become, although too many trees would create a lot of shade when they are larger, which can potentially increase water retention.  The nitrogen fixers can go in as soon as you can work the land in the spring.  You might be able to get them free out of ditches or on public land or wasteland on other people's property.  Don't worry if they are small; they might actually transplant better if they are not large.    

I wouldn't cut any trees on the slope above it.  This will only increase your abundance of water.  Top them if you need more solar, and/or at least plant others near them to take their spot when they die.  The more forest you have above your exposed clay slope the better.  Remember, slopes are meant to be forested.  That land wants trees!  Depending on your extreme sun situations, however, which sound like they might be intense at one time of the year, but generally are lacking due to clouds and rain, you might want to adjust your food forest plantings so that sun is getting down to some parts of the earth to dry it and nurture understory plants.

What I would probably do is dig drainage ditches across the slope, moving water east on one, and then west on the next.  This could also serve as a switchbacking wheelbarrow path.  Depending on just how mucky it is, make circular holes, and plant trees on the downhill side of the ditch, so that they get watered by the ditch underground.  Don't attach the holes to the ditch unless you see that the trees need more water.  If the slope is too mucky, then plant the fruit/nut trees and shrubs above the ditches.  Ask the nursery about the tree's needs and habits, and take note especially of any mention and ask questions pertaining to clay soils and high water content.  Some trees are not going to like that.  Some, like the pears, might.  

You might be able to buy bulk nitrogen fixers at the nursury, and some are easy to grow if you can get seed.  Plant lots of those if you can, they will stabliize your slope, draw water, and nourish your growing orchard.  You can always cut them down later if they become too much for you to do the work you like.  They will provide nitrogen if you chop down branches and lay them beneath your orchard trees (chop and drop) in two ways: one from the nitrogen fixing nodules on the roots that support the branches you are chopping, and two from the nitrogen rich material in the branches helping your topsoil to develop.

Your zone has a lot of options for trees, and shrubs!  Sounds like a fun project.  Good luck with it!  

...and welcome, again. Thanks for posting.  

I'll admit, i wasn't thinking huge hugelkulture structures, but microhugels - check logs. And i wasn't as clear as i meant to be: roughly on the contour, but intentionally off the controu to redirect water away from going straight downhill.

Here in a wet zone 7b the logs in my attempts at hugelkulture have rotted away very quickly leaving some very nice soil, when mixed in with the thin scrim of clay i was able to get over the mass. (I made the mistake of trying to dig through the clay when it was in brick stage.)

Sorry, Judielaine, I wasn't trying to criticize you, and I think you did say off contour somewhere there as well.  I meant to post this article in that last post of mind that explains the potential problem.  It's from Jack Spirko and is from Permaculture Research Institute: don't build hugul swales article

Huguls will turn to soil quick in a wet climate, for sure, and that's a bonus!  

Roberto pokachinni wrote:Hi Tyler...

Thank you SO much for this detailed response!  I have read through it a few times and love this plan.  Can you elaborate more on the circular holes you reference?  That's not something I'm familiar with.

I just mean holes.  Ha ha. I like circles.  Better than square holes.  lol.

Depending on your tree's water needs, either plant it in a (circular) hole above the ditch or below it.  Depending on how dry the slope becomes, you can tie the hole to the ditch with a small connector channel to feed the hole water.  

Roberto pokachinni wrote:Depending on your tree's water needs, either plant it in a (circular) hole above the ditch or below it.  Depending on how dry the slope becomes, you can tie the hole to the ditch with a small connector channel to feed the hole water.  

Ah I see now, thank you for clarifying!

Tyler Woodson wrote:

Eric Hanson wrote:Tyler,

I was actually thinking about some type of swale, even if just a short one.

Eric

This makes sense. I had kind of ruled out swales because of the steepness, but I think one right at the bottom before the foot traffic area may help.

Thanks!

The steepness of the slope screams terracing instead of swale/berm for water control. Water control needs to be addressed prior to any other part of your plan, otherwise you will find yourself undoing what you had done so you can get the water under control.
Instead of the bottom of the hill, start at the top, no sense in waiting for the water to do erosion damage before it hits any water controlling earth works. By moving the water along a swale (1 degree off level), you actually do more control in steep siturations than if you make a static holding swale (on contour) which can cause bigger issues such as a water plume at the bottom of the hill that creates a spring situation. Plantings will be easier to take care of long term by virtue of the water control constructs already being in place too.

Redhawk

Roberto, thank you so very much. Your detailed response clarifies a lot of what I have seen/experienced and reads like an excellent plan for the future of my own steep North-facing clay slope. Mine is pretty barren after experiencing a slide due to exactly what you warned about. Right before I bought the place a bunch of brush and smaller logs were piled up to "slow the water and erosion". Well guess what? They got heavy (filled with sediment) and presto! 10-20 yards of clay moved 80 vertical feet downhill. Then of course the next year 80% of the trees that got layered over died and fell over, causing more damage. Don't play around with clay slopes! That's my motto.

OP, thanks for posting this topic. We are in similar boats and you have helped me a lot. I haven't done too much with mine, dug some surface drains, yanked out a ton of half buried woody debris and used sandbags to create "reverse ditches" is about all so far. Basically I have just been collecting and steering the water away from the danger zone. I also had to put a few thousand sqft of plastic out to keep some of the stuff and the top light enough to stay there but I don't see that as being relevant to your case.

This year I am going to plant some trees and hopefully start rehab. On the hillside. Keep the faith!!!