How steep is too steep for a swale?

Hi, first time posting anything here so I am sorry if this is in the wrong place. I've recently learned about Permaculture and it sound like a very cool thing. My dad has a 9 acre property in central Mexico. He has recently gone to live there after about 20 years of living in the USA. I was talking to him on the phone a couple days ago and he commented that it has been raining over there and that there is a lot of runoff. I am wondering if digging a swale would help but I am worry about landslides or something like that. I looked online and found that the area gets about 400mm of rain annually. His property is on a northeast facing hillside and it's very rocky soil.  I found a site where I could make a contour line map that can give me an idea of how steep his property is and I have also measured the distance from the lowest point to the highest point on his property. The highest point is 2168 meters and the lowest is 2129 meters, the distance between the those two points is 247 meters. I am guessing that it has a slope of about 15 degrees. I have attach some images. Any advice is most appreciated.

I'm on a 15-20° slope and have found that swales are ok when that steep, you'll have to do multiple rows of them, tinkering with varying degrees of contour to account for overflow - in which certain areas can be deeper, etc. like catchment basins, then run-off into another basin/swale combo.

I also place rocks, and let thick weeds grow up in the areas that erosion starts to happen because I've found inevitably that nature has a way of seeking out to compromise our plans. A basic install with mapped out topography, then tinkering and modifying after a few rain/dry spells to work towards holding the water after you see the results of your work!

Trying to incorporate roads/paths among the hillside while still incorporating swales is a bit tricky but should be considered if you plan on maintenence or plantings.

Julio, you need to get in touch with another Cabellero Cervantes  family. They are located in Tlaxcala and in the past 70 years complete reforrested a wasteland and developed a method called the Tlaxcalal Method. Don Carlos, who passed away several years ago started the work but his children continued it. One son, Juan Carlos Cabellero Cervantes , got his degree in forestry and  his dissertation is available as a book and one of his daughters runs a permaculture education center. Their method rather than swales, uses a narrow trench of about 20cm on contour on very steep slopes.  To slow, spread and sink the water. They also collect local seeds of all types of plants that are growing and make Fukuoka style seed bombs and just toss them into the area after the trenches are dug. They do not direct plant trees, but they now have a forest.

Also you might want to visit, https://viaorganica.org/experiencia-de-restauracion-de-ecosistemas/ which might be nearer your father than Tlaxcala is.

Looking a bit closer at your photos, there is quite a lot of existing vegetation on the property. What are his plans? Just a nice place to live out retirement, or does he need to generate an income? Does he was to produce much of his own food?
I would identify existing vegetation that you want to keep and make a mulched basin around those trees. There's a very short kind of tree in the Mesquite family called Tehuitxle in Oaxaca, though I find plants have a lot of regional names in Mexico, but it looks a lot like what you have there. Left in its natural circumstances they only get to be about 3 meters tall, but I have one of these trees in my yard that is about 6 meters tall. They are thorny and want to shoot branches out low to the ground. But you can cut off all the low branches to encourage it to grow up. These give great shade, in order to get it to grow how you want you must prune often and giving it a mulch basin will allow the water to soak in.
I also suggest you check out Brad Lancaster's work https://www.harvestingrainwater.com/ He's located in Tuscan, Az which has similar rainfall patterns as central Mexico.

Cole Tyler wrote:I'm on a 15-20° slope and have found that swales are ok when that steep, you'll have to do multiple rows of them, tinkering with varying degrees of contour to account for overflow - in which certain areas can be deeper, etc. like catchment basins, then run-off into another basin/swale combo.

I also place rocks, and let thick weeds grow up in the areas that erosion starts to happen because I've found inevitably that nature has a way of seeking out to compromise our plans. A basic install with mapped out topography, then tinkering and modifying after a few rain/dry spells to work towards holding the water after you see the results of your work!

Trying to incorporate roads/paths among the hillside while still incorporating swales is a bit tricky but should be considered if you plan on maintenence or plantings.

There are a lot of rocks. Where should I put the rocks that I dig out when I dig the swale? uphill of the swale or downhill? Where would be the best place to put road?

Melissa Ferrin wrote:Julio, you need to get in touch with another Cabellero Cervantes  family. They are located in Tlaxcala and in the past 70 years complete reforrested a wasteland and developed a method called the Tlaxcalal Method. Don Carlos, who passed away several years ago started the work but his children continued it. One son, Juan Carlos Cabellero Cervantes , got his degree in forestry and  his dissertation is available as a book and one of his daughters runs a permaculture education center. Their method rather than swales, uses a narrow trench of about 20cm on contour on very steep slopes.  To slow, spread and sink the water. They also collect local seeds of all types of plants that are growing and make Fukuoka style seed bombs and just toss them into the area after the trenches are dug. They do not direct plant trees, but they now have a forest.

Also you might want to visit, https://viaorganica.org/experiencia-de-restauracion-de-ecosistemas/ which might be nearer your father than Tlaxcala is.

Wow, I'll try looking into that, thanks.

Melissa Ferrin wrote:Looking a bit closer at your photos, there is quite a lot of existing vegetation on the property. What are his plans? Just a nice place to live out retirement, or does he need to generate an income? Does he was to produce much of his own food?
I would identify existing vegetation that you want to keep and make a mulched basin around those trees. There's a very short kind of tree in the Mesquite family called Tehuitxle in Oaxaca, though I find plants have a lot of regional names in Mexico, but it looks a lot like what you have there. Left in its natural circumstances they only get to be about 3 meters tall, but I have one of these trees in my yard that is about 6 meters tall. They are thorny and want to shoot branches out low to the ground. But you can cut off all the low branches to encourage it to grow up. These give great shade, in order to get it to grow how you want you must prune often and giving it a mulch basin will allow the water to soak in.
I also suggest you check out Brad Lancaster's work https://www.harvestingrainwater.com/ He's located in Tuscan, Az which has similar rainfall patterns as central Mexico.

I got the pictures from Google maps, it's about 10 years old. I think the picture was taken during the rainy season, I was there last year, the vegetation looked less dense but maybe it's because it was the dry season. You are right about the regional names thing lol. My dad says there are a lot of Shashni and Capulincillo plants on the property. I don't know what Tehuitxle look like but there might be some. There are a few Mesquite and Huisache trees but they are small. There are also several wild cacti that produce fruit; prickly pear, garambullos, a bitter prickly pear that the locals call xoconostle,  a bitter sweet dragon fruit-like fruit that the locals call pitajaya, and other small barrel cactus. He would like to generate an income from the property but at the moment he just wants to stop the erosion, improve the soil and maybe in a few years start planting lots of fruit trees that can provide him an income. I plant to leave as much of the native vegetation in place for now, specially the ones that already produce fruit on their own. I been thinking of taking cutting from some of the cacti and planting them all around the property. Thanks for the advice about cutting the low branches to encourage vertical growth and about the mulch basin. Sorry I didn't reply sooner but I was very sick with Covid. I'll add some more pics of the vegetation on the property.

Vetiver grass hedges - They form a living barrier that slows and sinks surface run off, like a swale, produce biomass for building soil, and trap lot of sediment up hill of them. They incredibly strong and deep root system, and are used on steep ground to stabilise slopes.

The cope well with arid environments once established. They aren't tolerant of heavy frost, but I'm unclear if that would be an issue in your area.

Michael Cox wrote:Vetiver grass hedges - They form a living barrier that slows and sinks surface run off, like a swale, produce biomass for building soil, and trap lot of sediment up hill of them. They incredibly strong and deep root system, and are used on steep ground to stabilise slopes.

The cope well with arid environments once established. They aren't tolerant of heavy frost, but I'm unclear if that would be an issue in your area.

When would be the best time to plant them? I have done some research on the climate of the area and from what I found it seems that the temperature can get to the low 40 degrees Fahrenheit in December and January. I asked a family member that lives in the area if they have frost and she says it doesn't happen often. She thinks that the last time it happen was in November of 2018

Rocks go on the low side of swales.
Or build erosion prevention works with them.