Community Projects, Demonstration Sites, Earth Banks, Gabions, Land, Swales, Terraces — by Craig Mackintosh PRI Editor January 14, 2011
Do you remember Geoff’s recent Saudi Arabia consultation? Well, left behind in the Kingdom as project manager to implement the work is Neal Spackman. Neal has kindly followed up on my request for reports, providing the video and images below. After the video I’ll give you a little more swivel-chair commentary based on info I’ve had via email.
The new site recently sustained heavy rainfalls. Older locals said it was the biggest storm the area has seen in more than twenty years. It was great timing for the fledgling project, as it gave opportunity to show exactly where the incomplete system required more work, and where it was working well.
The following image of a road busted up by one of the flash floods gives a decent concept of how much rainfall suddenly descended down hillsides largely devoid of any vegetation that would otherwise slowed its progress and reduced its destructive force:
Neal said that the earthworks already established, or semi-established, held up a lot better than he expected considering the deluge. He goes on to give some details that will interest the earthworks-oriented permaculturists out there:
1. The series of 8 gabions in the main wadi washed away in the flood, with the exception of the first and last gabions.
2. The water hit the flood plain with force and overflowed the previous wadi boundaries. Five of the gabions we had built to direct water into the swales were bypassed, four were completely buried, and the swales filled up halfway with silt.
3. We need to rebuild and fortify the initial series of gabions, rebuild some of the gabions that were supposed to direct water into the swales, and build earthworks for all the water’s new entry points.
1. The swales captured approximately 9.75 million liters of water (assuming 6.5 kilometers of swale, water 1/2 meter deep — which is what the lines show and how much silt got in — and 3 meters wide).
2. 80% of the mountain gabions stood through the storm and have started accumulating silt fields on the uphill side. Some of the silt, even at the very top gabions, is still wet 9 days later. This means water is still flowing under the earth onto our demonstration site, and that we succeeded in slowing it down.
3. All the terraces stood through the storm, and have started to create flat spaces and silt build-up.
4. Based on this test, we can improve our water system before we plant our forage/food forests, resulting in a better water system and a safer site for the rest of the project.
As many of you will know, water is the first aspect to think about when designing a new site. And a site as radical as this, where all of nature’s moderating features have been chopped down, dug and/or chewed up, and you’re dealing with steep inclines and sudden rain events, reversing the destruction and designing for stability can be challenging. Neal’s ongoing experiences, and Geoff’s subsequent visits will be interesting indeed. I’ll probably tag along with Geoff at some point as well to give this project even further coverage. Given the future currently facing many dry regions, from Saudi Arabia to Australia to California, etc., these examples are worthy of our attention and collaboration so as to increase our collective knowledge for their restoration.
Once the water soakage situation is in place and stabilised, expect to see this area start to re-green! With local cooperation, there’s really no reason the forests cannot return, and with it, rain.
I’ll put a few more pictures below so you can see some of the work going on to date.
Terracing to collect silt and slow and soak water
The shallow slopes don’t require a lot of digging to terrace. Collected rocks start
the process of silt collection behind them — self-flattening over time
A rock wall gabion slows the water and collect silt to build fertility
After rain events have passed, the silt can be moved where it’s needed
Large on-contour swales create temporary water storage and soakage points,
ensuring the flows stay long enough to benefit the area, whilst reducing
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