Most of us know that swales are conventionally constructed as a ditch with some of the following characteristics:
- On a slope
- Downhill berm of uncompacted soil
- Seeded to prevent erosion
I have an alternative idea:
Suppose you met the preceding criteria by importing artificial topsoil and mounding it in the place where excavated soil otherwise would have been.
Consider the following:
A. A financial/ecological/time-spent cost is associated with renting/buying equipment to dig a swale, or dig one by hand
B. Introducing topsoil increases organic matter available in depleted soils, which is what most of are/will be working with
C. A financial/ecological cost is associated with trucking in topsoil
1. In situations where the costs of line C is less than or equal to the costs of line A, then this alternative method may prove an advantageous alternative to the conventional method of constructing swales
2. Where existing organic matter is scarce, high costs in line C, relative to line A, may still prove a long-term advantage
Check out an ongoing experiment in permaculture and community: Dancing Rabbit Eco-village
Well, first off not all swales are level (on Contour). A gentile slope where the water runs no faster than you can walk (normal speed) is common. They are constructed level in aired climates for complete water retention.
I don't know about your area, but in mine trucking in top soil will run you much more money, and possibly the same in carbon emissions as digging the ditches on site. Also there is erosion to consider, when digging a ditch you naturally slow down the water running down a hill, before it hits your pile of soil. Just placing soil in a raining climate would be a wash out.
I suppose in the right local and for the right situation just 'adding on' instead of digging would be an option to consider, but it is riskier in my opinion.
Location: AR ~ozark mountain range~zone7a
posted 8 years ago
heck ya 'clean fill' in TX, 30 years ago use to be nearly free, just stick a sign out by the highway, I doubt it is like that anymore. But still even $300 for a big load of sure enough dirt, is probably better than what ya got. Just be kina careful that the dirt your getting isn't full of round-up or some other really bad stuff, go to the dig site if possible! I wouldn't worry about rain washing out your stuff too much, but if it become a problem, a flat shovel will scoop it back up pretty easy. Some old tree trunks or batter boards make a pretty good, easy raised bed boarder. I live on a gravel hill, digging it really isn't an option for me either, the existing ground is very hard, rocky, I used some rail road ties on top of the ground as a 'temporary form' to put the dirt up against. Once the erosion & settling has taken place the heavy ties will be removed and the trench filled with new trees will replace where the ties were, (kind of like an already dug ditch).
If your slowing the run-off down, and even holding it there...your doing it right.
Running a financial analysis is always a good idea. I bring in topsoil ingredients like DG and sand and chipped trees and wood and mix them with my own compost to make the soil perfect for whatever trees I'm planting, so for me it's a matter of quality. I can always make my own compost and hugel beds. Green-waste is free. Just construct compost bins where you want the topsoil and then build your hugel beds with the compost in a few months (a year if you don't turn them). But you'll need to do some digging into the dirt or mounding with fill dirt under your topsoil to create water capture zones. If you just mound topsoil over sloped dirt, the water will just run off under your topsoil mounds.
'Science is the father of knowledge, but opinion breeds ignorance.' - Hippocrates