I live on Vancouver Island on the West Coast of Canada; a temperate maritime climate (similar to Seattle). We get over 75 inches of rain a year, with 80% falling between October and May. We rarely drop much below freezing (January average low is 0.3C/32.5F) and summers are mild (average July high 22.5C/72.5F) with little precipitation and sunny days. We receive nearly 2000 sunshine hours annually. The Köppen scale would place us as a Csb climate (Dry Summer Temperate Maritime), with typical maritime Cfb not too far distant (north and western parts of Van Isle).
I’m seeking resources and information on earthworks for my particular climate. I’ve found lots of great information for Deserts, Drylands, Cool Climate and typical Temperate climates. However, I have found almost nothing regarding earthworks as it pertains to the Csb climate type. At first I assumed that recommendations for other climates would be pertinent for my area, but a video with D. Doherty suggests otherwise (
). As always in Permaculture, it depends…
My analysis of why typical earthwork solutions may not be appropriate is as follows:
• Swales are intended to slow surface water flow and allow the water enough time to infiltrate the soil.
• Many climates struggle to reduce erosion due to reduced plant cover.
• Most Permaculturists advocating swales are based in climates where sporadic large precipitation events followed by substantial dry periods are a significant concern, often these locations are either historically not forested, or have been largely deforested.
My situation seems fundamentally different:
• We receive sustained, light precipitation for 7-8 months of the year, with very little precipitation during the summer.
• We have very few ‘large’ precipitation events.
• Much of the region is heavily forested (mostly coniferous with some deciduous) and soils are easily able to absorb precipitation levels.
• Surface flow is not a concern, neither is bare soil; if anything we suffer from over vigorous plant growth as well as pooling of water and seasonally boggy ground.
Can anyone suggest resources, videos, books, papers, contact info, podcasts, etc… that deal specifically with Permaculture earthworks in Dry Summer Temperate Maritime climates? I am loathe to expend the time/money/energy creating earthworks verbatim if they are truly inappropriate for my climate and region. Can anyone point to instances where it was tried and it worked, tried and modified, entirely other approaches were used?
I do plan to post this question to multiple sites, apologies if you run in to it more than once.
TL,DR: Standard Permaculture Earthworks seem inappropriate for Temperate Coastal, Dry Summer areas. Can you suggest earthwork resources specific to the particulars of this climate?
When I see an adult on a bicycle, I do not despair for the future of the human race. ~H.G. Wells
I have been thinking along the same lines...
I think part of the answer is water storage with swales.
I live in the Puget Sound area (Mason County). I have a smaller plot that is currently in pasture for the chickens. I have considered adding the following
1) Water storage from rainwater collection - 10K to 20K gallons
2) Small pond at top of topography with outflow (80-160 gallons/day over 120 days) recharged with the rainwater collection as need during the summer
3) Swales to maximize water movement. swales planted in perennials (fruittrees, berries) and selected annuals for human and animal consumption.
4) Small pond at bottom to reclaim any excess.
I am also very interested in learning what swale, keyline or other water management system works the best for this climate/area. Haven't seen any specific resources on this but hope to get some info at my upcoming PDC!
Location: South Puget Sound, Salish Sea, Cascadia, North America
posted 5 years ago
I think some of it depends on if you have clay to work with. Lots of glacial soils don't have enough which increases costs of surface storage. Surface storage is much cheaper than a tank for irrigation if you have a slope. I think in our climate the best first step in Permie Zone 1-2 might be grey water, which goes to waste all summer long. In our climate a lot depends on landscape position.. if you are on a water shedding site, or a water receiving site. If you harvest and store for irrigation, you are getting into water rights issues. Winter diversion and storage may be easier to permit. Capture for percolation or wetland restoration is legal. The historical forested ecosystem had near ZERO runoff... every drop was either evapotranspired or percolated.
Paul Cereghino- Stewardship Institute Maritime Temperate Coniferous Rainforest - Mild Wet Winter, Dry Summer
I wish I had answers but I share your questions. We are purchasing 10 acres just across the strait from you on the Olympic Peninsula of Washington State.. We have little slope (20 or so feet across the entire property) and silty, very deep soils that should do well at holding some water - but we are in the "Rainshadow" and have only approx 25 inches of rain/year, and like you mostly in the winter.. We are thinking of rainwater harvesting but there will be some restrictions as it is a critical aquifer recharge area regulated by the Dept of Ecology.. Also looking at earthworks.. Will continue to follow this thread..
I live west of Portland, Oregon, and have the same situation. We get about 40 inches of rain a year, almost exclusively between October and May. Very little precipitation from mid-June through mid-October. Soils are silty/clay. We have very little runoff, but by mid-July, the soils are dry 6-8 inches down, even in the shade.
I have wondered about swales, but I wonder if it would just make a big mudhole for nine months out of the year and a rock hard ditch the other three months. For small scale plantings, I have wondered whether a hukel bed would extend the moisture through the summer, but on a large scale, that seems impractical.
I am interested if there are any general suggestions for this type of climate with the types of soil that are common to Cascadia. I will be watching this thread.
Hukel beds will hold the water well. Just make the hukel bed on contour like a swale. Ideally your hukel bed will allow overflow water to go by it at a certain level, which will prevent high flooding in the winter. Acts like a rain garden with the berm as a hukel bed.
"You mustn't be afraid to dream a little bigger..."
I've been looking at off-contour swales (or as Tom Ward calls them, Keyline Terraces), which move the water across the slope so do not contribute to excessive bogging. Then move the water to a hyper saturation point: pond, wetland. The point being to simultaneously keep good drainage in some areas, while intentionally soaking others. On-contour swales are about even distribution of water across the landscape, which we really don't need in boggy springtime. And the point of an on-contour swale is typically to establish vegetation, a means to an ends. So if you already have forest cover, then a water harvesting structure meant to establish vegetation is redundant.
Thanks Dave and Andrew. I had considered either keyline or off-contour swales or beds as a means to gently move the water where needed. Thanks for clarity on the idea that swales are meant as part of the vegetation establishment process. I do need to establish vegetation. I am working on a concept of alley-cropping, perhaps somewhat similar to what Mark Shepard is doing, but I am in the early thought processes here.
Although I have dabbled around the edges of Permaculture for about 10 years. It has only been the last several months that I have really started to understand things to the point that I'm starting to know how little I really know and conversely, how much I need to learn.
Location: Corvallis, Oregon
posted 5 years ago
I think of a on-contour swale as a feature that is on-it's-way to a small vegetated terrace, once it eventually fills in with organic matter and silt. A swale enables vegetation to establish, which then becomes the sponge itself to replace the earthwork, with roots, woody structure, and ongoing generation of organic material to cover and shade the soil's surface and intercept the flow of surface water. In the long term, the swale disappears and is replaced by a widening band of vegetation.
Andrew, if one wanted to establish forages (for grazing ruminants and poultry) in an alleyway type system between swales or hukel beds, would it be better to do the keyline approach (off-contour) or on contour swale for hydrating the forages between. I've wondered if it is possible with earthworks to keep forages green throughout much or most of the summer without irrigation in the Willamette Valley. Apologies, I don't mean to hijack the thread.
Location: Corvallis, Oregon
posted 5 years ago
I think if you're keeping the animals off the pasture in wet periods and just super-hydrating pasture areas using on-contour swales and waiting to bring the animals on during dry times, then they're doable.
The issue with contour swales here is that the area below the swales becomes a seasonal wetlands during rainy periods. So it's about the timing of the animals in those periods. Off contour swales up from winter forage areas, and then on-contour swales above summer pasture could be the appropriate pattern so you keep low areas green into summer and don't wreck pastures through compaction when soils are at field capacity.
I've been thinking a lot about this myself, and have been doing recent designs with this exact issue in mind, and I've chosen to keep swales off-contour. On-contour swales are also dangerous with gophers/voles who will drain the swale with sub-surface tunnels, where off-contour swales are not keeping a long skinny pond of water full of water for an extended period. This has in large part been from the recommendations of Tom Ward, who plans more from the flood damage and over-saturation perspective for this climate then the "harvest every drop" one.
I live in the same type of region (just NE of Portland, OR).
We had a permie landscape designer do a design for our 1/2 acre sloped backyard. She included something she called "log checks", i.e. place logs more or less on contour (staking them if they might roll downhill), and cover them with soil. Their primary purpose is to collect leaves from trees farther up the slope, but also to slow and store water (like a hugelkultur). I haven't built them yet so I cannot say how effective they are.
If you live in or near a city, there is a very good chance that you could get large quantities of wood chips from tree services (for hugel beds, contour mounds, or mulching). I never have any problem getting free wood chips where I live. I have about 40 yards of chips in a pile in my yard right now, and they wanted to bring me even more but I told them to stop.
I also have a small pre-formed pond which is basically an experiment. It begins to dry up in July, and if I did not re-fill it, it would be completely dry by early August. So evaporation is a huge factor starting in July. Personally I think it is probably better to store the water underground (i.e. in rotting wood) or under heavy vegetation (extremely well shaded pond), otherwise much or all of the water you store is going to evaporate.
It seems that the PNW climate, with wet winters and dry summers, is perfect for hugelkultur. The wood under the soil will get saturated, will hold the water and release it (particularly to long rooted plants). Plants that don't like wet feet can be planted up high on a 6 foot tall hugelkultur berm. Plants that like more moisture will be happy further down.
I've got a hugelkultur bed that I built this winter/early spring, and the plants on it (tomatoes, potatoes, pumpkin, strawberries, nettles, blueberries, ferns on the shady north side) are doing great. I have watered it a a little, I figure much of it didn't get a chance to be fully saturated and most of the wood isn't that spongy yet.
I too share the disappointment in little information, exploration, and implementation of earthworks in the PNW maritime climate. It does seem a little more challenging than other climates. I have a client in Port Townsend that looks set to invest in a medium size earthworks project this year. It will be a pond at the top of the slope, with swales situated every appx 20 ft going downhill, silvopasture style like mark shepard. We would like to install it as a workshop, which would be a great opportunity for everyone in the region to participate in maritime earthworks. We would plant it out immediately like sepp holzer. We are seeking input from others on ideas, experts, excavator drivers, and so forth. I will keep you updated with information as things unfold.
Location: Corvallis, Oregon
posted 4 years ago
I want to share a really interesting discussion about on-contour swales in the PNW with Darren Doherty when he was here in Oregon doing a Regrarians training in September. Darren really questioned the appropriateness of on-contour swales in our climate, because of the typically high rainfall and clay soils in the region. Basically a contour swales becomes a wetland strip that becomes choked with wetlands vegetation. If this is what you're trying to accomplish then that's fine, but otherwise keyline plowing will harvest a lot of water into the soil for less expense and without the fragmentation of pasture and super-saturated strips that a series of on-contour swales will create. I've stopped putting structures on-contour myself, and use earthworks like roads or swales to subtly move water to a collection point instead of infiltrating it evenly on-contour.
I believe that Huglekulture is also a great method for water retention in this climate. Holding water in the soil in spongy wood is perfect, just like it is in a forest. Lots of bio-mass added to beds, such as wood chips and mulch to get through the dry July-September period. A pond to store rainwater for summer irrigation, if well sealed, would be a great idea as well. This is a perfect region for trees and shrubs, but annuals are pretty demanding for irrigation in my bit of experience at home. I am good at growing perenials, terrible at any annuals that need too much care. Too occupied in the summer enjoying the sun and forget to water:( The woodcore beds I have built seem to help that immensely.
We certainly don't want to create anerobic, boggy areas. Gross!
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