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Managing an 10 foot drop on our land - need suggestions, advice

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posted 7 years ago

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We purchased 2 acres recently, and are building a house there this summer, and want to incorporate permaculture in the development of the property.

Fully half of an acre is in a gully that follows the north side of the property, and then drains into a culvert that passes under the main road. At the lowest point, the bottom of the gully is at least 10 feet below the rest of the lot, creating an earth "wall" that isn't quite vertical, but its pretty darn close. You can't get up it without using hands as well as feet, and going down is more of a slide than walk. There are several trees RIGHT on the edge of this which appear to have helped in soil stabilization, but have many roots exposed. Our neighbor's property rises from the bottom with a manageable slope; there is no scouring or 10 foot walls on their side of the gully.

What do I do with this? How do I keep it from getting worse, or even more ideally, improve it to make it useful in some way? I should mention that our entire lot slopes towards this area, dropping 8 feet across the 200 foot width of the lot before the 10 foot drop-off. There are two smaller, still walk-able gullies running into this larger one that are also a concern, as I'm sure they will continue to get larger.

Any suggestions or references appreciated.

Cori

John C Daley

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Photos will be needed to help.
If you can get some that would be great.
I need to see what is causing the drop prior to offering solutions

John Daley Bendigo, Australia The Enemy of progress is the hope of a perfect plan
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Cori Warner

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posted 7 years ago

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Ok, Will go get some tomorrow. Thank you!

rob macintosh

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Location: Alberta, Great White North zone 4

posted 7 years ago

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First get something growing on it to stabilize it i had a simular bank although only 4 feet high. I put down some pasture seed with lots of rye grass in it to hold the bank together. But if it is to shady or acidic grass might not work for you.
You need to slow the water rushing through this gully. Most of the time this is a problem that starts at the niebour 6 places up and gets worse till it gets to you.
You can throw things up against the banks or make a series of dams to slow the water and try to get it sinking in and stop erosion. You will be suprised how much soil and organic matter piles up if you slow the water.
Ofcourse this all depends on how much water we are talking about.

Cori Warner

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I found some photos on my phone backup, and uploaded them to a Facebook album here:
https://www.facebook.com/pg/TanglefootFarmOK/photos/?tab=album&album_id=197559491043051
Click on the photo, I labeled them in the captions.

Thank you,
Cori

Cori Warner

Posts: 39

posted 7 years ago

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rob macintosh wrote:
You need to slow the water rushing through this gully. Most of the time this is a problem that starts at the niebour 6 places up and gets worse till it gets to you.
You can throw things up against the banks or make a series of dams to slow the water and try to get it sinking in and stop erosion. You will be suprised how much soil and organic matter piles up if you slow the water.
Ofcourse this all depends on how much water we are talking about.

Hi, Rob. Thanks for responding. Weirdly, this starts about 10 feet from my western property line, and ends at the culvert on the east property line, so it's about a 350 run. The really high wall is only on one side; the neighbors have a relatively gentle slope to the bottom of the gully.

I drew a cross section here https://scontent-dfw5-1.xx.fbcdn.net/v/t1.0-9/31960869_197566234375710_7370136228936548352_n.png?_nc_cat=0&oh=fe9f432b880d05d561da3315d960ebe4&oe=5B57722A I just don't know how to dam it up; there isn't really two edges. However, I could for sure work on the two smaller cuts.

Thanks!

wayne fajkus

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posted 7 years ago

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Is this a ravine where all the water concentrates to a relatively small width. Or is this a very wide drop off where water sheets over a very large range?

Sometimes the answer is nothing

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Cori Warner

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wayne fajkus wrote:Is this a ravine where all the water concentrates to a relatively small width. Or is this a very wide drop off where water sheets over a very large range?

From what I've seen, including just after a rain, it appears to start in three fairly wide drop offs, and where these converge, the water starts moving narrowly (about 2 feet wide) and quickly, scouring that south wall as it goes along. It finally hits a large fallen tree, which has caused a small deeper area, and then it follow that tree about 3 feet until it overflows into the actual drainage culvert.

wayne fajkus

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Book. Water harvesting for drylands, vol 1.

It covers ways to build soil using rocks. It discussed and had a solution for large drops, but its too confusing for me to describe. Its not one and done. Each rock layer ads sediment. Then another row is added. I guess the good part of it being gradual is the work load is spread out over time.

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Cori Warner

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wayne fajkus wrote:Book. Water harvesting for drylands, vol 1.

Thank you! Found and ordered on Amazon!

John C Daley

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It is not as bad as I thought it maybe.
The one thing that could cause problems for you is very intense rain causing a large volume of high speed water pouring over a waterfall.
What happens then is the base of the waterfall is eroded backwards, causing the top [ overhang] to break off, thus perpetuating the problem.
I think yours is not too bad, I would not be digging around of the lower surface, but perhaps take steps to slow the movement of water on the top.
This can be achieved with logs, rocks in a wall etc.
Research under soil erosion, preventing gully erosion, and I think you will get good info.
If its possible to add to the vegetation on the slope that may help, but I think it looks pretty good.
Would a plan of the area be possible to draw to see the shape of the problem?

John C Daley

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What does the image with the red soil show?

Michael Cox

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What is your location and climate like? What is the soil like - sandy? Clay?

Generally when dealing with surface water flow the best approach is to start upstream of the problem and slow the water down. Living barriers like vetiver grasses work very well, and help stabilise the soil and prevent erosion. Otherwise you might consider swales on contour to hold and sink water. Once these are in place you will find it considerably easier to rehabilitate the bank and channel itself, because the force of the water will be considerably reduced.

It was hard to tell from your photos - how much water, and catchment area, is there upstream of you off the property? Or does the gully start on your own land?

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Anne Miller

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The pictures look like you have grass growing which is good. More grass might be better. Everyone has given good advice.

This link is to a thread which show what some folks have done with rocks. With some forethought and research rocks could be incorporated to keep the soil from washing.

https://permies.com/t/85178/dry-stack-retaining-wall

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Cori Warner

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John C Daley wrote:What does the image with the red soil show?

Hi, John. That is a pano of the lot; the gully is in the treeline on the right of the picture. All of Oklahoma is "Red Dirt" country, due to the high iron oxide content.

Chris Kott

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Hi Cori.

You've been given good advice, I think. Starting at the top of the flow onto your land is the best idea, I think. Slowing the water is key.

I like the idea of using sedimentation dams in the gully. These can be made of rocks, as mentioned, and often, with faster flows of water, those are needed just to withstand the current, but I would suggest that larger woody debris can be used upstream of those rocks. I would even venture to suggest that you could make a finer sedimentation barrier on the upstream side of any rock/log dam you create with a staked row of rectangular straw bales. These would act as literal filters, trapping finer sediment and organic matter, building up the dams until you have a series of sedimentation pools.

If there's enough erosion from off of the properties upstream, these could eventually fill to some extent with the sediment that they're trapping. Or you could look to see if keeping a series of shallow pools there could benefit you in some way.

In terms of the hillside sloping into the gully, I would suggest staking branches and logs on contour, especially if there are any less-steep parts of the slope. Catching sediment in these on-contour sediment traps can act to create terrace-like formations through sediment deposition, allowing for more varieties of plant to thrive on the slope, also stabilising it more with vast intertwined root mats.

Good luck, though, and let us know how it goes!

-CK

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Cori Warner

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Michael Cox wrote:What is your location and climate like? What is the soil like - sandy? Clay?
It was hard to tell from your photos - how much water, and catchment area, is there upstream of you off the property? Or does the gully start on your own land?

Hi, Michael. the gully starts on our land, and ends at the culvert that crosses under the main road. It looks like the neighbor upstream might have done some dirt work, because it literally starts at my fence line. It's abt 350 long. Once the water goes under the culvert, it continues through the neighborhood until it joins a larger creek and leaves the neighborhood.

Our soil, like most of Oklahoma is sandy clay with streaks of heavy clay. When is rains, it holds water for days, but by summertime it turns into brick. However, it only holds so much & right now it's tornado season. Rain comes hard and fast during the storms, and flooding is common. The storm last weekend dump 2.5 inches of rain in less than 3 hours. Our annual rainfall is 36 inches, and we will get 1/3 of that in May and June.

Swales are stage 2 of our plan for the property, and we'll start them as soon as we finish clearing the brush so we can dig them. There is a giant dead oak tree at the head of the gully that I am thinking I could have cut down, and then use to create some dams, and slow down the water. I suppose the brush we are cutting could be used for that purpose as well.

Michael Cox

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Hi Cori,

So the gully starts on your land, but there is water flowing on to your land from further up the catchment? That could be a problem stabilising the gully, as you don't really have control over that water, and those flows are likely what is eroding your bank. I would start by controlling your own water flows and see what happens in the gully once that is under control.

I'm not familiar with your climate, but a quick google search shows that you get some frosts in winter? Vetiver prefers warm climates, but can survive mild frosts. Look into vetiver hedges planted on contour for trapping water, sediment and building organic material. There might be other grasses in your climate that would serve similar function.

Regarding the gully itself, brush dams MAY serve your purpose, however they may also divert the water and exacerbate your problems:

From what I've seen, including just after a rain, it appears to start in three fairly wide drop offs, and where these converge, the water starts moving narrowly (about 2 feet wide) and quickly, scouring that south wall as it goes along. It finally hits a large fallen tree, which has caused a small deeper area, and then it follow that tree about 3 feet until it overflows into the actual drainage culvert.

Where it hits the tree you are seeing scouring as the water is being concentrated in one area. If your dams aren't well thought out they could trigger similar scouring events. Start with small experiments, observe carefully during rain events and see how it works.

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John C Daley

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I would leave the old tree in situ.
Apart from holding the soil it may be a haven for animals and roosting points for birds.

Chris Kott

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I would look at what the water is doing. If the tree is encouraging erosion, it should be removed, or it will continue to encourage erosion.

It may do much more for soil retention as a series of logs and branches laying across the path of the water, acting to slow it down and collect sediment.

I would advise against sentimentality if the position of the tree is causing the removal of material downstream.

-CK

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