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To swale or not to swale  RSS feed

 
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So we bought our property (in Southern New Hampshire) about 2 years ago and have been sort of idling on getting our garden up and running. Part of this was wanting to observe the natural flow around here, and part was financial and logistical planning.

We recently just got a tractor though and now my husband is chomping at the bit to finally do some terraforming in the garden area that we've been planning on doing from the start. The previous owners had made garden beds using granite curbs as liners. This made moving them to rework the space very difficult before but now that we've been able to move the stones out of the way, I finally need to make up my mind on what we are doing in the garden. When we first moved in, I was pretty deep into permaculture research and was convinced we were going to do swales and berms. However, after observing the property, I'm starting to wonder if swales are practical in our situation. A few things:

The west side of our property slopes gently into a wetland area that is also part of our property. It's more of a wetland during the summer, but a pond in early spring and fall into winter when it rains the most. (it is fed primarily from the mountain range that is directly west of it) The yard area closest to this wetland is actually pretty saturated for a long while after lots of rain, parts of it almost always stay squishy.

Though we have had fairly dry conditions the past couple summers, I don't think any of our vegetation is actually very thirsty. The water table most of the year is actually fairly high considering we have a sump pump in our basement that runs most of the year.

Most of the soil around us is extremely rocky and clay heavy (another reason we've been hesitant to start digging pre tractor). The area closer to the wetland is not too surprisingly much richer and dark but it still seems to have drainage issues, whether this is from the soil material, or the water table just being higher there, I'm not sure.

I've attached a google view of the property to try and illustrate this somewhat.

I still am fairly certain I want to do some sort of raised beds. But I'm beginning to think that swales on contour may make more problems than actual benefits. I was originally thinking fairly shallow swales anyway, but without the swales, we'll definitely need to introduce more organic matter in order to build up any raised beds.

Looking for any advice on the matter or opinions. Let me know if something needs further clarification. Just want to make sure we're making the right choices before we dig up our yard.

Thanks so much!

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gardener
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Location: Central Oklahoma (zone 7a)
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Hi, D, welcome to Permies!

To a man with a tractor, everything looks like an excuse to dig.  Boy do I wish I had one!  But I am a firm believer that swales are wonderful ... only when you can answer the question "why do I need one right here?" firmly and confidently.  And it does not sound like you are to that point, certainly not yet.

Indeed, from the sound of your description and the look of your photo, it's not manifestly obvious to me whether swales are a place you will wind up going.  You've got a nice property there but I'm not hearing the level of design confidence yet that says "time to do large-scale earthmoving".

I don't know if you've got the budget or time or inclination to get a permaculture designer to come in and sketch up some ideas for you, but it might be worthwhile.  If local legalities allow, my thoughts are that you ought to consider turning that wetland below your garden into an actual pond, which could dry out the rich but wet soil just uphill from the wetland, serve as garden water storage for future dry spells, give you a place to raise ducks or catfish or something similarly aquaponic, be a nice beauty feature, and probably serve a dozen other functions I haven't thought of because I'm not a permaculture designer.  It just seems like a huge feature of the property that somehow could be designed into greater functionality.
 
D Tomlin
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Thanks for the reply Dan!

I do need to look into local ordinances on the wetlands here in NH. I know in MA there are very strict rules on setbacks in regards to wetlands, and it might be similar here too where they want the waterways as untouched as possible. We have a beaver dam at the outlet of our wetland, that was busted up a bit in a storm last year. It primarily is what retains the water during the wetter seasons. We've talked about trying to restore it since who knows when the beavers will be back,  but our pond feeds into our neighborhoods larger pond community and I worry they'll take notice if we start withholding water in the dry months.  (A prev owner told us a story about finding a guy from the pond community on his property with an ax, trying to bust up the beaver dam during a drought !) We also have a neighbor that owns the back half of the wetland,  so we'd have to be on the same page about any changes. Although I'm sure she'd prefer having water more often

You are right about not having a "why" for the swales.  My main reasoning for it was that they come up constantly in my permaculture research, and always sound like a good practice,  but I do doubt its usefulness in our environment.

I might look into a designer for help. But we have a pretty hardy diy spirit so it can be hard for me to outsource something that I want to learn and understand myself.  I definitely don't want to go another year without a garden though. So maybe starting with the raised beds is enough for us for now.

I am still curious if anyone has direct experience with this sort of environment and swale applications. Or any permaculture ideas in marsh like conditions.  
 
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Location: Alberta, Great White North zone 4
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I vote hugelkultur on contour in your garden area. Assuming its not dead flat, in which case build it any direction you like.
Try digging a hole about 2 or three feet deep where you want your garden and see if it fills with water.
That marshy area is basicly a swale already i wouldnt worry about more water catchment for your garden area.
If your water table gets higher than 2 feet for extended periods id be thinking raised beds aswell.

Now if you could make some more dams up that stream from you then we would be talking year round stream.
 
D Tomlin
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Hugels on contour is where I'm leaning,  but I was reviewing holzer' s book and he mentions not putting raised beds on counter to allow for drainage.  Maybe he's talking more extreme slopes?
 
pollinator
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Location: Los Angeles, CA
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While you may have plenty of moisture, swales do more than just infiltrate water into your soil profile.  They also capture soil as it washes down the grade in a big storm, and they build soil as they capture biomass (leaves, weeds and such) that tend to dry up and wash away in a heavy rain.  

Is there room for both swales AND raised beds?   In your northern climate, i'd think that raised beds would be a must to get your crop into the ground ASAP in the spring as well as to extend the growing season for as long as you can in the fall.
 
Posts: 339
Location: Australia, New South Wales. Köppen: Cfa (Humid Subtropical), USDA: 10/11
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From the description, it seems there's not a lot of elevation between the house and the wetland, and the water table is predominantly high?

Swales on contour are primarily intended to slow the flow of water, capture it and allow infiltration. This seems contrary to what is needed - if the ground becomes supersaturated it's likely to go anaerobic.

Hugels may also create the same issues unless they're raised beds above ground, not trenched in place.

Raised beds across the contours, with the Swales actually used as drainage ditches that taper downhill on the ends should keep the ground moist but drain excess water down diversion trenches to the wetland e.g. Convex or C-shaped beds with the ends downhill.

Reeds or other water loving plants placed in the trenches may appease the neighbours concerns of nutrient leeching, etc.

 
gardener
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Before you start putting in swales you need to identify the key point, that is where the most water starts the journey downhill, then follow that path to see how best to control the flow of the water in a heavy downpour.

I would recommend renting a subsoiler or buying one used first, that lets you have the opportunity to do some soil structure rehabilitation and open some deeper channels for nutrients and microorganisms to get down into the soil and start doing their magic.
Once you have done that, you will be in a better position to determine if you want shallow swales or deeper ones, where you need to put shallow ponds or if you even need them.
The tractor's implements are how you judge the width of the alleys you make (they need to fit nicely between the swale and berm structures).

The closer you get to the "swampy" area, the better hugels will work for you.

Redhawk
 
D Tomlin
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Marco Banks wrote:
Is there room for both swales AND raised beds?   In your northern climate, i'd think that raised beds would be a must to get your crop into the ground ASAP in the spring as well as to extend the growing season for as long as you can in the fall.



I believe there is room for both. We have about 120 feet from our deck to the rock wall bordering the pond/wetland. I had originally thought a berm and swale right before the rock wall, to allow for planting some more fruit trees and shrubs to act as a windbreak. (We get some MONSTER gales off of our mountain in the transition seasons). And maybe another one 50 feet further out, roughly in the middle.

I do believe the area closest to the wetland is fairly anaerobic atm. There is definitely a stagnant feeling to them. But we have had an unusual 3 weeks of nearly daily rain, so I wouldn't say it's a typical thing for it to be THIS marshy, at least not at this point in the summer.

The slope is relatively mild down to the pond. My husband thinks it's 1:20, but I think it could be closer to 1:15 in spots. I'll try and do some surveying this week to figure out exactly what it is.

I'm not too worried about stopping erosion in that part of the yard, I've never noticed wash outs after storms, but then again it is pretty well seeded with grass and weeds at this point, so once we disturb it, that may change. I do still want to help get the water into the pond easier. So i do like the idea of tapering the ends into a channel of sorts that leads to the pond.

I'll look into the subsoiler idea! Would this mean basically tilling most of the area and then cover cropping it for a season?

Thanks so much you guys , this is great! I'm still torn on the swales, lol, but I'm really enjoying the range of opinions!

pic: the yard looks pretty beat up atm from the tractor, and also from the granite being relocated, but this is the space currently.
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