I've done a lot of permaculture (and related) tinkering and reading over the years, but I don't have a great eye for overall macro-scale earthworks yet. Can somebody with a bit more experience tell me what I could do to hold water on a decent scale on this site, images below? Preferably higher up in the property, but I'll work with what I can get in a reasonably cost-effective way.

It is an odd property, mostly a grassy SW-facing hillside, mixed hay/wheat currently with a bit of timber in back. Total around 105 acres, annual avg rainfall 24", elevation ~3000ft, located in inland NW, USA. Cold med climate, we get all our rain from October to May with little over the summer. SW prevailing winds around here, so it is somewhat exposed. Haven't dug much yet but well digger reports in the area indicate there is a deep layer of clay under the topsoil.

It isn't marked, but contour lines are 10' -- the hill is fairly steep at points.

Thanks for the comments! Sorry for the lousy graphics...

Hi J.F.!

What a coincidence, I just posted a while ago talking about a way to help people like you.
http://www.permies.com/t/40205/rainwater/Simulating-rainfall-water-catchment-usage

Sounds like a good way to test it out. Do you have a high resolution image of the contour lines or satellite image?

Hi there! I just knocked the above images up in Sketchup -- I don't really know how to use it beyond the very basics, and the contour data is from Google Earth. I can certainly create the above at a much higher resolution -- the contour lines will still be 1px wide, so it should be more precise. How big do you need? Do you want the terrain removed (just contour)?

the images should be at least 1000px wide... but if you can get it higher than that, great.
I need the contour lines only, but you can give me a separate one with just the terrain, maybe I can use it t make the final image prettier

I PM'd you a link to the files, since they're 10mb together. Let me know if that'll work for you.

got it! looks good!
only problem with the contour lines is that there are no numbers indicating the altitude.. I dont really know whats high or low :/

Yeah, sorry -- numbers not included The lines are 10 ft degradation. The far right near the bottom is a small peak, and the rest of the map is basically a hill descending from that (right to left). If it is too incomplete for you to work with, don't worry about it

well my technique for modelling from contour lines is harder than expected, this was a good training. still some research to do.
can you just check this rough video quickly and see if I got the elevations right?

https://www.youtube.com/watch?v=PzpwntPJKiI

Yep, that terrain looks right. Indeed, tech projects are never as easy as they may first seem. That last 20% takes a lot longer than the first 80%

ok, so here is a first test with "rain"
http://youtu.be/s3ZK4AQ8odU

I've embedded the video below for you.

thanks!
and here is a still shot with the contour lines visible.
http://i.imgur.com/kwA2wZr.jpg

Swale effect: http://imgur.com/a/0oLxS

Please don't forget, there are plenty of mistakes in this simulation because it was done quickly and roughly, just to try out and see how the whole thing "feels". A real case would have taken much longer as the contour lines would need to be modelled perfectly (which was not the case in this one

Hey, that effect is awesome! I like it! That sort of thing could be quite helpful for a landowner, and definitely for a designer that they could show as part of their presentation to a client -- if you could streamline the process you could probably sell it.

A few observations:

* The lines aren't quite right, as you say. Overall it is quite good, but I see a few places where the water flow doesn't line up with what it should be doing based on the contour lines or the landscape. Doesn't matter here, as this model plus the contour maps give me a good idea of what is happening.

* I think it would be needed overall to take into account not just what falls on a property, but also rainfall onto the catchment area that *drains into* the property. In my case that isn't such a giant difference since I'm nearly at the top of the butte (and anyway I didn't give you maps that included that data), but in most cases this is where the majority of the flowing water comes from, and it can make modeling just the direct rainfall quite misleading depending on the terrain.

* If you could sanely model potetial dams and swale flows, that would be *extremely* helpful to people, I think

* Overall a steeper camera angle looking into the land is more useful (my opinion, at least). The tilt and pan is slick, but I expect the most valuable view is probably a top-down fixed look.

* I like it!

* I wish this property had better dam sites in the top half. The only natural spot my amateur eye sees in the top half is in a deeply forested gully/thicket, so damming it would be hard and overly disruptive. There is also a small spring or seep in there I think, which needs further exploration.

I know this is a far less hi-tech solution, but I wanted to very quickly summarise some of the stuff Geoff Lawton teaches in his PDC, and also in his earthworks course, about choosing a dam site. Basically, he says to look out for contour lines that make a shape like this.



Please excuse my total lack of drawing skills. Also, the highest land is at the top of the image.

Then remember that water always flows downhill, at right angles to the contour lines. Something like this.



So in this case, most of the water falling on the land would find its way to the area inside that inverted-horseshoe shape contour line. Which also has a conveniently narrow 'neck' across which to build a dam.



Which would then fill up like this.



The course gave a whole load more info on calculating how much water would be collected and details on the actual construction, but I thought a quick visual might be useful to some people. Even if it's not exactly the eye-candy that Nuno produces.

J.F. Sebastian wrote:Hey, that effect is awesome! I like it! That sort of thing could be quite helpful for a landowner, and definitely for a designer that they could show as part of their presentation to a client -- if you could streamline the process you could probably sell it.

A few observations:

1- The lines aren't quite right, as you say. Overall it is quite good, but I see a few places where the water flow doesn't line up with what it should be doing based on the contour lines or the landscape. Doesn't matter here, as this model plus the contour maps give me a good idea of what is happening.

2- I think it would be needed overall to take into account not just what falls on a property, but also rainfall onto the catchment area that *drains into* the property. In my case that isn't such a giant difference since I'm nearly at the top of the butte (and anyway I didn't give you maps that included that data), but in most cases this is where the majority of the flowing water comes from, and it can make modeling just the direct rainfall quite misleading depending on the terrain.

3- If you could sanely model potetial dams and swale flows, that would be *extremely* helpful to people, I think

4- Overall a steeper camera angle looking into the land is more useful (my opinion, at least). The tilt and pan is slick, but I expect the most valuable view is probably a top-down fixed look.

5- I like it!

6- I wish this property had better dam sites in the top half. The only natural spot my amateur eye sees in the top half is in a deeply forested gully/thicket, so damming it would be hard and overly disruptive. There is also a small spring or seep in there I think, which needs further exploration.

1 - right,as I said,it was just a quick test, not a perfectly made model
2 - definitely! when planning water you should have a big picture of where water comes from, you should know what exactly is your watershed. Of course a watershed can be a HUGE things (dozens, hundreds? of miles), so we need to find a balance between perfect and do-able
3 - yes, that is the plan
4 - yeah, the pictures are nice, but I plan to make the top-view maps, especially in maps where main waterflow lines are represented.
5- cool
6 - why dams and not other earthworks?

This property and landscape is mostly suitable for pasture/silvopasture and livestock. It is a brittle landscape. Swales are critical here for slowing water and keeping it infiltrating on the property, and I think if it were affordable some keyline plow subsoil ripping would be very helpful...but those both store water in the soil (not a bad thing). Animals, irrigating individual sections during our dry summers, and fire protection (a real concern) on the other hand all require surface water, and that means a dam. High up means I can move the water where i want with gravity. Down low it would need to be pumped, which adds complexity, cost and maintenance.

I could put large cisterns up high on the hill (and probably will) but in this environment cold winters means they will freeze unless they are mostly underground...which makes installing them much more expensive.

If the topo map you included is correct there aren't many places on this property that are under the recommended maximum slope for earthworks of 18%.

The guideline i heard was 20%, but indeed you are correct, most of it is right around that grade or steeper. The soil does have a lot of clay, which probably makes things more feasable than if it were sandy at least.

where did you guys got those values from? there are always solutions to be applied , at least until 50%

I think I saw it in one of Geoff Lawton's video series. Nearly anything is possible of course, but at some point the law of diminishing returns applies especially for broad scale construction: too expensive for too little gain.

From the designers manual, page 231 " 20%- Moderate; usually accepted as the maximum slope for safe cultivation and erosion control; wheeled tractors are used at about 18%. The maximum slope of good road surfaces is accepted as 13%; anything over this should be concreted or sealed."

I agree with Sebastian, anything over 18-20% becomes too costly (especially on broad acre sites).

Top-down view waterflow map, overlayed in the satellite image. Here it can be seen the swale effects on surface water coming from rainfall.

Pretty neat. And a very useful single image.