permaculture

["Tim Winton" <winton@nor.com.au>]

Hi Antonio,

 

I am sure that you could find a suitable ground cover plant which will grow in your area to help keep the surface sand from eroding- this is a good strategy, but it will only work within limits. You will also need to shape the road to reduce the volume and speed of the water during heavy falls, then a good ground cover should do the job of holding the surface in place to stop erosion channels from forming. Water moves material as a factor of volume and speed. Good road design seeks to minimize both.

 

Here are a few general suggestions:

 

Put “roll over” in the road where the slope is steep (say over 12 degrees). A roll over is a bump or mound built up on the road surface which is just off perpendicular to the road direction. This sheds water off to the side before it can build up speed and it sheds it before it can join with other water to build volume. The bump should be formed with the road grading/repair machine next time it is fixed. The bump is about 250mm high and1000mm in width. It is as long as the road is wide. Put them every 10m or so or closer where it is steeper.

 

Put “diversion drains” down the sides. Normally roads are “crowned”- that is made with a convex profile so that water sheds to either side of the center into ditches. These ditches need to be diverted off to the side so that water cannot build volume or speed. Diversion drains are cut in using a grader blade or dozer bucket. They start in the ditch and head off at an angle toward the side of the road then they turn more sharply to disperse the water over a wide area by being very nearly on contour. They are generally about 5m or so until the turn and then maybe another 3 or 4 meters where they shed the water. The idea is to divert the water from the ditch, where it is traveling fast down the hill and disperse it in a flat sheet onto the side to the hill away from the road.

 

Put diversion drains at roll overs where possible.

 

If the road is traveling along the side of a hill it is also possible to shape the road without a crown so that the water just sheds to the downhill side of the road. If you have a crown in a road traveling along the side of a hill, then the water on the up hill side needs to be dispersed (usually by putting a pipe under the road every so often).

 

Try and find a good earth moving and road grading operator- they quite often know how to make a road last as long as possible. Then it may just be a case of establishing a ground cover before the nest big rain event start the erosion channels.

 

I hope things are going well for you Antonio. Good to hear you are still working in the field.

 

Cheers

 

Tim

 

-----------------------------------

Tim Winton

www.permaforesttrust.org.au

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Message: 2

Date: Sat, 8 Nov 2003 02:09:47 +0100

From: "Antonio Scotti" <antonio.scotti@tiscali.es>

Subject: [permaculture] Access road run-off control strategies.

To: "pc-list-ibiblio" <permaculture@lists.ibiblio.org>

Message-ID: <000e01c3a595$19871860$ed93fea9@it>

Content-Type: text/plain; charset="iso-8859-1"

 

 

Hi all,

I am facing the question of how to improve the access road status to an orchard/veggie garden using a low energy/money approach if it exists, and suggesting other methods if the low energy ones cannot be considered efficient in the long run.

 

Basically it is a downslope road, (we are in a mediterranean climate),

whose material is basically coarse sand, meaning that during heavy rainfall events

(and less so during normal precipitations) part of the road soil drifts downhill, opening long erosion scars.

For the people owning the road it means rearranging the roads conditions some 3/4 times a year, by carrying sand loads on site and reshaping it with a buldozer or such machine.

 

What low energy techniques are there to improve this road's conditions? What other techniques other than the one I outlined above there exist?

 

Would it be possible to grow some "very short" ground level, herbaceous plants whose roots

hold the soil in place? Does it make sense?

 

It could also be interesting capturing the run-off water (without the silt) at the lowest point somehow.

 

Cheers

Antonio