[Scpg] steep permaculture slope ideas?

[Dan Hemenway]

Hi Kevin:
    I'm afraid that I've shot my wad as far is advice on this one goes.  I'm not  in California and I've only worked there a few times.  Since there are huge climatic, landform and ecological differences from one part of the state to another, I am not qualified to provide examples. I know the principles, but you need local people for the particulars. I have vague notions about the Santa Barbara climate, but I'd want hard climate data, for example, before recommending anything but natives naturally growing in similar conditions. Carob is a relatively small tree--the ones I've seen in Spain were about 20' more or less.  If you've read Yeomans, you know that you want taller trees on the slope to increase humidity and possibly precipitation.  Some non-woody plants might serve also, e.g. or more of the many Agave species, which I'm guessing to be deep rooted judging from their adaption.  Of course guessing won't do, because you have a very sensitive area. The problem with herbaceous plants, of course, is that they are short-lived, compared to trees, so the roots die.  They may be useful as a temporary expedient to hold soil while tap-rooted trees, many of which are slow growing, take hold. Possibly your slope already contains the necessary vegetation to hold the soil in place.  
    No good permaculture designer is going to make recommendations without visiting the site.  Inquiries such as yours are good for eliciting directions for further consideration, but familiarity with the site is paramount.  I'm not familiar with any books or other authoritative information resource that gives good data on plant root structures, except in a general way.  
    But whether the information is available or not, you need it to design and implement responsibly.  Try the local forestry people, for starters.  Local colleges with landscape departments may have people who can give you a list of suitable species, or tell you where to find one.
    One thought that comes to mind is almond.  Also in Spain, I saw these in road cuts.  They were established on the crown of the slope, and sent their roots deep. When the road was widened, or when soil slipped, the exposed almond roots sent up new shoots and colonized the bank with a network of roots and trees from top to bottom.  These cuts were about 20-25 feet high, if my memory holds. I have a picture of a mature root sprouted tree on the cover of one of our journals (The International Permaculture Solutions Journal) as a matter of fact. I have no way of knowing if the original almond trees were transplants or were seeded in place, and that could make a difference.  


Black locust performs similarly, by the way, but in damp situations such as the outside curve of creeks and rivers where they retard the rate at which the water cuts away the bank.  But they would not do on a dry site.  But there are local people who know what plants do this in your area. You just have to hunt them down.


Good luck


Dan Hemenway





-----Original Message-----
From: Kevin Gleason <kevin at kevingleasonart.com>
To: Dan Hemenway <permacltur at aol.com>
Sent: Sat, Sep 4, 2010 10:20 pm
Subject: Re: [Scpg] steep permaculture slope ideas?


Thanks Dan,
I really appreciate all of your advice.  I like mesquite, but it can grow enormous here in Santa Barbara.  I like that it would help fix nitrogen into the soil.  What would be some small "pinning" trees or shrubs?  Carob sounds fun... does it get very tall?  I know that fruit trees have spreading roots, but not sinking ones.   
Enjoy your weekend,
Kevin




On Sep 4, 2010, at 9:27 AM, Dan Hemenway wrote:


 
 
 Clay soils can turn to Jello when saturated.  Stability depends in part on rock content and in part, as has been suggested, on vegetation.  In the Phillipines and in Catalonia (Spain) I had the opportunity to see road cuts next to pines native to each region, exposing the roots.  They were like giant push pins, except that as you looked down the powerful and long tap-root, every few feet roots radiated out horizontally in whorls, so the tree was both holding the soil in place and pinning it deep, probably to bedrock.  In Luzon (Philippines), where the forest has  been cut for charcoal (by people displaced from the land, trying to feed their families), soil was sliding off the mountains in sheets.  This was a cascading catastrophe, reaching out into the coral reefs and harming everything between.  But I digress. 

 
 
My thought is that the most responsible action would be to establish trees and maybe tap-rooted shrubs such as mesquite. (You don't give much in the way of climatic clues.)  If you want food, try drought tolerant species such as carob, maybe olive, etc.  But have those push-pin trees in place first.  If you don't know what to do, I strongly advise against shaping the earth.  You just don't have the experience.  I wouldn't try it without an expert consultant, and I've been practicing and teaching permaculture for 30 years around the world.  If the slope is already carrying the amount of trees suitable to rainfall, you might very gradually replace them with trees and tap-rooted shrubs more useful to you (or your client, it that is the case. Again, no info.) Whatever your do, do not install swales on the slope!  They will concentrate water and blow out and create erosion gullies.  Do not install swales anywhere near the crown of the slope, if you have control of that also (no info), as well, or any other water catchment system.  The slope is too steep and clay is too erodable.  If you decide on terraces, which I strongly advise against, have them slope gently away from the hillside, so that they shed water.  (This is advice I received from Willem Smuts, a geologist and permaculturist who knows a lot about these matters.)  Grade them precisely, keeping them exactly on the contour around the hillside, but as I said, with an exceedingly slight slope.  That way, they do not saturate in a rain, or at least are far less likely to saturate than a level terrace or, absolutely the worst in this cases, a terrace with a berm or an inward slope.
 

 
 
Sometimes, it is best not to mess with things, because whatever we do may cause problems.  This is the case with efforts to try to control watercourses.  And I think it is probably the case with your steep slope. Good luck. 
 

 
 
Dan Hemenway
 
Barking Frogs Permaculture
 
 
 
 
 
-----Original Message-----
 From: Owen Dell <owen at owendell.com>
 To: Kevin Gleason <kevin at kevingleasonart.com>
 Cc: Wesley Roe and Santa Barbara Permaculture Network <lakinroe at silcom.com>; scpg at arashi.com
 Sent: Fri, Sep 3, 2010 7:03 pm
 Subject: Re: [Scpg] steep permaculture slope ideas?
 
 
 
First, check with a consulting geologist about whether your slope is stable 
enough to accept the destabilization and additional water loading that comes 
with terracing. I've seen too many incredibly expensive disasters resulting from 
inappropriate slope modifications to not speak up on this one.

Owen

Owen E. Dell, ASLA
Owen Dell & Associates
Landscape Architect • Educator • Author
P.O. Box 30433 • Santa Barbara, CA 93130
805 962-3253
owen at owendell.com
www.owendell.com


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Fountain, Portland, Oregon) 

On Sep 3, 2010, at 3:47 PM, Kevin Gleason wrote:

> Hi all,
> 
> I was wondering if anyone has good advice for creating a garden on a VERY 
steep slope (more than 45 degrees.)  I'd love some feedback on alternative 
terracing methods, whether this is too steep for small swales, good 
soil-holding, drought-tolerant  ground covers and other plants that would be 
useful and other ideas.  I remember hearing Brock Dolman talking about making 
retaining walls with burlap tubes filled with soil and a little cement.  Anybody 
tried it?
> 
> Thanks for your help!
> Kevin
> _______________________________________________
> Scpg mailing list
> Scpg at arashi.com
> https://www.arashi.com/mailman/listinfo.cgi/scpg

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