[Scpg] steep permaculture slope ideas? Now also: general site analysis
Dan Hemenway
permacltur at aol.com
Wed Sep 8 14:09:37 PDT 2010
Well, you went into more detail than I wanted and raised some interesting points. It is reassuring that you concur with me that raising food may not be the
best option for this site, except for suitable tree crops. The only one I am confident would be suitable is apricot, because of its root-sprouting habit when soil
around the roots is disturbed, eg., after some subsidence or gully erosion. The long establishment time of tree crops also favors stabilization before human
traffic. In a garden, one wants food in as many months of the year as possible, but here traffic for food production and harvesting seems quite undesirable.
I am a bit concerned, on reflection, about the suggestion of net and pan by another contributor. I think one would do well to develop some skill with this over gentler slopes. If I recall
correctly, this system was developed in the Mid-East drylands, historically, on very stony soil. I suspect that the grades were not as precipitous as described for this site. Net and pan was practiced in the context of a whole culture which had generations of accrued experience on the landscapes involved.
I have developed a 20-page questionnaire that I license to clients, with a full credit if they complete it, and with other provisions. A major purpose of the survey
is to bribe, if you will, the client to learn much more about the site, climate, etc., than perhaps s/he had thought about. If the client is not willing to do his/her own
legwork, they are not going to properly implement anything that I design, wasting my time. I've got plenty of work to do at home. After I review the answers to
the questionnaire, usually on the plane en route to the site, I can do a better site walk or walks (depending on lots of factors--usually I'm on site for at least one full day.)
I always advise the client that costs will be less and results better with a training event where participants develop a site plan based on the client's desires. The client
also gets training, and participates in the development of the design, so better understands how permaculture works and has a deeper grasp of why the design
calls for certain actions. Optimum is for someone to be well trained and then live on or near the site for at least three years, during which experiencing the site is
a major objective. Three years isn't much, admittedly, and as you point out, causative events that can precipitate catastrophes may be on the order of decades or
centuries. A knowledge of local natural history is thus extremely beneficial. Yet in three years in places were people ought to live at all, which does not include precipitous
slopes, people can get in tune with what is going on while acquiring a lot of objective knowledge as well. And three years may be the limit for most people's patience
to forebear from irreversible actions.
All that notwithstanding, I think that the original question was useful, and reflected a sincere effort to act responsibly by soliciting additional advice. It is possible and
practical to start with principles and then revisit the specific site and see if they apply. I'm sorry to say most of the principles I've learned have come from observing
when the Earth is mistreated, such as the deforested slopes that I mentioned in the Philippines, and then determining, from observations of factors such as root
structures of the pines of the are, why the subsidence was a new factor, consequent to deforestation and probably the traffic, mainly foot traffic in this case, to haul
out wood to burn for charcoal.
Dan Hemenway
www.barkingfrogspermaculture.org
-----Original Message-----
From: Owen Dell <owen at owendell.com>
To: Dan Hemenway <permacltur at aol.com>
Cc: jcalvert at crystal3.com; scpg at arashi.com
Sent: Wed, Sep 8, 2010 9:36 am
Subject: Re: [Scpg] steep permaculture slope ideas?
Yes, it's vital to be on site in order to understand what is specific to that
particular situation. What is the soil type? What is the nature of the
underlying geology? What plants, native and introduced, are currently on site?
What is the native and introduced fauna? What is the aspect of the slope
(N/S/E/W)? How much if any water runs onto the site from elsewhere? How much
water soaks into the soil and how much runs off? Where does the runoff water go?
What is the history of the site in terms of land use, erosion problems, soil
movement, fires, etc.? There are many questions to be asked, and most people
don't even know that these questions exist. That is why I caution that in
addition to seeking site-appropriate strategies, a knowledgeable professional be
consulted when working on slopes where poor decisions can lead, literally, to
disaster.
True success comes partly from knowing what is local and particular to the site.
Each site is unique. There are no general, non-local conditions; there are only
principles that can be applied to local conditions. And true success is measured
in centuries, not months or years, of stability and health of the system without
the need for external inputs.
Type conversion of any given piece of land from one ecosystem to another is not
to be done without taking into account many factors. Some land is not suitable
for production, or for various reasons it is not safe or wise to disrupt the
native conditions. I assert that no form of human intervention, even
permaculture, is better for any given piece of land than the original native
ecosystem. Permaculture is a fit practice for healing disturbed and urban lands
and making them productive, but when it encroaches upon wildlands it becomes
just another pernicious human activity. Agriculture in general is a massive
wipeout of ecosystems that have evolved for millions of years. Agriculture
supplants complex ecosystems with overly simple, totalitarian ones that depend
on the continuing brutal exclusion of all forms of life that are not of
"economic value." To be in harmony with our surroundings, we should be hunting
and gathering, removing individual food units from intact wild ecosystems.
Unfortunately, there are far too many of us for that to work anymore, but it
remains the one truly environmentally justifiable way of surviving. It is what
all the other animals do. As a result of our overpopulation, we are forced to
turn to various forms of agriculture to meet our needs. Permaculture is helpful
as long as it remains within its proper bounds, but it is important to
understand that all forms of agriculture, including permaculture, are
destructive.
I mention all of this because the original posting was about growing food on a
slope. I know nothing about that slope, but if it is in or close to a native
condition I would, were I on site as a consultant, probably advise against
destroying the native flora and fauna in order to grow food. Chaparral or
coastal sage scrub lands in our area are not particularly or not at all suited
to any form of agriculture, and the stability of such lands is often dependent
upon the extensive root systems of native plants. Therefore it is my opinion,
consistent with commonly accepted good practice, that such areas are best left
alone. Not to mention the fact that wild places, however homely they may seem to
the casual observer, perform essential ecological services that cannot
necessarily (or in most or all cases cannot ever) be replicated or improved upon
by human manipulation. And of course, there is the matter of the morality of
destroying wild places, on which I am adamant that such destruction, in the name
of any human cause, including permaculture, is wrong. We must not use
permaculture as a rationale for ruining natural systems.
On the other hand, if this is a disturbed slope which has not been in a native
condition for some time, and if I were assured by a geotechnical expert that
there was no risk of either surface erosion or landslides (called, dramatically,
"mass wasting" in the profession), I would certainly consider some form of
productive use. Most likely my approach would concentrate on low water use trees
and shrubs and perennial plants, since it's very challenging to grow annual
crops on sloping terrain. But I would also urge that restoration of the native
ecosystem be considered. (Of course, in our area there is also the matter of
fire, and when people move into wildland interface areas they create the
conditions for destruction of wildness in the name of fire safety. That is a
whole other big question that I won't get into here.)
Looking to one of the specific strategies under discussion here, grasses are
indeed a diverse group of plants. Because many grasses, particularly annual
species, are shallow rooting, they form a slip zone at the interface immediately
below the bottom of the root mat they develop. In the absence of deeper-rooting
shrubs and trees, there are no roots below 12 inches to help consolidate and
hold the soil in place. The number of stem penetrations per square foot in a
grassland runs in the thousands (compared to one or fewer stem penetrations per
square foot for shrubs and trees), and the individual grass blades act as tiny
funnels to channel rainwater into the soil. This results in supersaturation, and
the slip zone becomes lubricated. Due to the supersaturation, the soil becomes
both heavy and plastic. Eventually, gravity overcomes the diminished friction at
the slip zone, and the entire mat of soggy soil and grasses slides downhill. In
an unstable soil, the lack of roots in deeper horizons can result in a far worse
outcome than mere loss of the foot or so of surface soil; the entire mass of
soil down to a depth of many feet can collapse onto the area below.
I should also point out that mass wasting can occur after many years of
seemingly successful type conversion. It takes years for the root systems of
native plants to decay to the point where they have stopped performing
soil-holding services. It is common that some time after a piece of land has
been turned to agriculture or urban landscaping, it will "suddenly" fail. This
happens all the time, and people are mystified as to the cause. It is simple:
the fine and delicate equipoise of the native conditions was interrupted, with a
catastrophic outcome. We mess with land at our peril, and at the peril of
others.
I hope the above information is helpful to all. There is, of course, much more
to this. I am happy to continue the discussion and to hear dissenting opinions.
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
QUOTE OF THE DAY
"O take heart, my brothers. Even now...with every leader & every resource &
every strategy of every nation on Earth arrayed against Her -- even now O even
now! my brothers, Life is in no danger of losing the argument! For after all...
(as will be shown) She has only to change the subject."
Kenneth Patchen
from Hallelujah Anyway, 1960
On Sep 7, 2010, at 2:14 PM, Dan Hemenway wrote:
> Owen:
> If it isn't practical, it isn't permaculture. That's basic. That's not
to say that the word isn't misused, but that is not the fault of the word, or
the practice that the word represents.
> Grasses are a huge family and quite variable. I was silently skeptical,
myself, about a plants that are largely mat-rooted holding soil in place on a
steep bank. "Bunch" grass could be any of hundreds of species. On the other
hand, with the correct woody plants, grasses may be OK. We are talking too much
in generalities here, and the specifics of site and of habit of candidate
species for the site are important. Neither you, nor I, nor anyone who has not
visited the site can know what will work. On the other hand, I am profoundly
skeptical of an approach that favors surface runoff, since that is just another
way of saying soil erosion, particularly on steep slopes.
>
> Dan Hemenway
>
>
>
> -----Original Message-----
> From: Owen Dell <owen at owendell.com>
> To: John Calvert <jcalvert at crystal3.com>
> Cc: scpg at arashi.com
> Sent: Mon, Sep 6, 2010 1:29 pm
> Subject: Re: [Scpg] steep permaculture slope ideas?
>
> Grass is a very poor way to protect slopes against erosion. The large number
of stem penetrations results in a very effective transmission of water into the
soil, which can lead to supersaturation and slope failure. No offense to anyone,
but I recommend that people not speculate about what is going to work. There are
accepted standards for this kind of activity. Permaculture is a great thing, but
it doesn't always address real-world issues and it isn't always right. Slope
failures can cost hundreds of thousands of dollars to fix, and the cost is not
covered by insurance. I say again, PLEASE consult a professional before you go
off implementing half-cocked ideas.
>
> 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
>
> QUOTE OF THE DAY
>
> "You take a number of small steps which you believe are right,
> thinking maybe tomorrow somebody will treat this as a dangerous
> provocation. And then you wait. If there is no reaction, you take
> another step: courage is only an accumulation of small steps."
> George Konrad
> Hungarian novelist & essayist
>
>
>
> On Sep 6, 2010, at 10:23 AM, John Calvert wrote:
>
> >
> > I was gonna say grass... the bunch grass sounds like a very good idea.
> >
> > lfunkhouser at juno.com wrote:
> >> Kevin,
> >>
> >> You might also want to talk to Mary Scaran, who is an acupuncturist >> in
SB (she's in the phone book) and has a very steep slope running >> the entire
length of her oak wooded and desert upland property that >> is permeated by a
spring. She has planted lots of things to >> stabilize, including Persian
mulberry trees (edible!) and some kind >> of grass -- can't remember which --
but a type of bunch grass that >> she selected for its very specific properties
of soil >> stabilization. Mary practices permaculture, studies horticulture, >>
and is a very fine acupuncturist.
> >>
> >> Good luck.
> >>
> >> --Laura
> >>
> >> ---------- Original Message ----------
> >> From: Kevin Gleason <kevin at kevingleasonart.com>
> >> To: John Calvert <jcalvert at crystal3.com>
> >> Cc: scpg at arashi.com
> >> Subject: Re: [Scpg] steep permaculture slope ideas?
> >> Date: Mon, 6 Sep 2010 07:14:15 -0700
> >>
> >> Thanks, John, and all others who have replied. This is such a >> helpful
community. I am going to look into the "net and pan" >> technique Susan
recommended and am trying to find some good >> "pinning" shrubs and trees per
Dan's advice. I need to pay good >> attention to the plants that seem to be
holding up west facing >> slopes next time I'm out hiking. It is okay with me if
this >> really steep section doesn't grow food.... Maybe I'll just grow >> food
for the birds there.
> >> I appreciate eveyone's help.
> >> Thanks!
> >>
> >>
> >> On Sep 5, 2010, at 9:22 PM, John Calvert wrote:
> >>
> >> >
> >> >
> >> > I started out writing a response to this, looking in the >> direction >
of what grows native on our steep coastal mountain >> canyons.
> >> >
> >> > But I realize that there isn't much edible on the really steep > >>
slopes. It seems the more fruit-bearing types are more likely to >> > appear
where there's better soil and moisture.
> >> >
> >> > So, that leaves the plants that do well in poor soil and least > >>
moisture...
> >> >
> >> > nopal cactus, various wild sages, maybe fit in a hollyleaf >> cherry, >
chia ?, maybe some kind of mulberry, wild golden currant >> (?).
> >> >
> >> > so, mostly natives, and then some select fruit-bearing plantings >> w/ >
drip irrigation. ?
> >> >
> >> > JC
> >> >
> >> >
> >> > 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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> >>
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