Our "Rocks" After a Heavy Desert Rain

Hi, just doing a quick postmortem. the first check dam shows the classic undercutting of hydraulic fall velocity when water drops from height it digs a hole on the down slope side of the check. [–MM_...] that is where the rocks on top fell into that hole. The fix is simple. Go lower, let the water ease off the check dam slope down on the downstream and slope up on the upstream. […mMm…] big stones in the middle, small stones on the up and down slope. Even if you do this if the check is too high the water will cut around the sides into the banks. Weight and Velocity is not Our friend. Weight increases with height and velocity increases with the fall from that height. Two things slow down water, obstructions (rocks) and Ironically (water). Look at any engineered dam they always have a plunge pool. Some might think “I will just dig a hole” bad Idea, it pre undermines the dam and increases the fall from the top. Best solution, Remove the stones from the top of the check dam and build a smaller dam close to and below the original dam. [….M..m….] instant plunge pool. Rather than going higher Go lower but use more smaller lower check dames in closer intervals to each other [ m…m…m…] close enough that the water will back up to the dam before (Water slowing water) Going too high with the gabions did two things, it undercut the gabions as it cut out the bank. The bank soil filled the undercut hole. If you look closely, you will find that the water did not push the gabion over, it fell into its own hole. […..MM...] [….##...] As I now see it, the angle of the gabion is just about right (angled up angled down). Look at all the clear space above the gabion that filled up and came over the banks imagine that as steps up like a fish ladder [ …...mMm……..mMm…….mMm…….) Ripples in a slues box. By using the same amount of material as in the Gabion spread out up the river will hold an slaw the same amount of water. (Weight and Velocity is not Our friend) The only real rule of thumb is don't try to stop too much in one spot as a gallon of water is about 8.3 pounds and about 7.5 gallons to a cubic foot so a cubic yard of water comes in at 1,680 pounds think how heavy the rocks are, they are not that heavy. Lower not higher. Nothing really failed out there, it just pointed to doing something different.

You should try setting up cameras to watch the water when it does rain. You'll learn a lot by just doing that

I think the rat's nest did better because it allowed some of the water to flow through, kind of like the idea of a willow tree bending in the wind while an oak tree may break

The key to building a secure check dam is always the pyramidal cross section. A good rule of thumb is that it needs to be twice as wide at the base as it is tall. The good news is that there's no need for a dozer to come in. All you need to do is go upstream a few feet and rake/hoe the gravel and dust down to the dam wall. This creates your "ramp" front, but also creates a depression that tumbles the storm surge, forcing it to surrender some of its erosive power. Just make sure to build a rock ramp on the downstream side of the dam so the overflow doesn't scour the ground and undermine your whole structure. You're basically mimicking what beavers have done for millennia. Of course, the dams work best when there's a bunch of them. That's why I always recommend starting at the top of the property and working your way down. Build them by the dozen and you'll surprised at how well they do by the time you get to the other end of the wash.

BTW every time you rebuild a rock structure, it will be better than the previous version. I've been dry stacking rocks for 20+ years.

I'm wondering if why your "rats nest" worked so well is the same reason beaver dames work. They are leaky weirs. If the water has a way to keep moving forward, it won't washout the banks so badly. I'd build a few more of them higher up and closer together for maximum impact. You have learned a lot with this first rain, and you will learn more with the next one. Good Luck

I don’t normally comment on videos, but I just wanted to say thank you for always being willing to take the failures as lessons on how to do better, and for continuing to try to make a difference. It would be amazing to see your vision come through so that some of these species on the brink have some chance at life. 🖤

Build them shorter and more frequent, That's how you avoid failure and rebuilding and rebuilding. Brad Lancaster gives very good instructions so the water doesn't undercut, etc --as well. That silt looks great.

Piles of brush = rudimentary beaver dam and beavers are the original land regeneraters. Not a terrible idea to keep using what dead brush you have around to use in conjunction with the rocks.

It appears that perhaps multible small check dams in each drainage could prevent the washout of the large one at the end thus more water would be saved

A great way to add organic matter to the desert floor is planting the right kind of trees/ bushes. Palo Verde, Desert willow, Texas honey mesquite, golden lead ball tree, acacias, mountain Laurel, Apache plume etc. And by planting these kind of trees/bushes you will also start attracting more pollinators which attract birds which will help with seed dispersal and you might even start getting game animals moving in looking to use the shade and cool ground from the trees. Great work out there! You're embarking on a great life long project!

Nice work! Thanks for the gabion tour :) Indigenous people in southern AZ placed firmly rooted long posts, with a bit of a gap between their placements (maybe a foot or so?), across the washes to divert and slow the water for farming. The debris naturally built up when the storm water carried it and created weirs, similar to beaver dams. Very minimal work for high return! Modern adaptation could be t-posts or something similar.

If there was a possibility to slow down the water further up when the streams are smaller it wouldn't hit your barriers with such a force. It know it would be ton of work but I think lots of smaller barriers where the water first gathers might help in slowing it down. I think the guys who built all the wee dams in Nevada ended up building over 20,000 in a 20+ years time period.

Fascinating. I am really enjoying watching what you are doing. Little by little, step by step, you WILL achieve your goal.

At least the water is showing you were it wants to go!

This reminds me of something i did yrs ago I live on rd that had a huge ditch in My yard cause by county rd department It was wash out I ask them to fix it the of course said no So I got down in the 8 ft ditch started adding small dams each Was bigger than the last Everyone said jack it wouldn't Work But each rain brought in more soil An living plants Within a yr the ditch was gone All I done was piled rocks But the best part it made my yard Alive I got grass a couple of small Trees which I didn't plant any of it So it caught on an people around Me started doing same thing in the county made ditch where it had ruined our yards Now ditch are all piped an cover over This was all do to a pile of rocks

Regarding the damns, you need to build one each time the elevation decreases 1m (3 feet) or so. You don't need big damns, one feet height is more than enough if you build several so you can slow the flow of water enough while allowing the stream to flow down through out the whole system. You want as much moisture to feed the soil but also to feed as much land as possible as the soil there is not going to be able to absorb much water itlf it's very dry.

Thank you for the update. Surprized that a bunch of sticks and organic material hold back water really well...all the beavers in the world are going...well duh...:D To this day it always surprizes me how much power water flow has. Rather than bulldozers...a few rebars driven down in the cage and rocks area?...well only if you can't get the dozer in there.

Construct more rat nests near beginning of streams spacing close together , when stream bed is wide build some rock islands staggered near center of stream beds add more to the dry rock dams.

I have found stacking brush in run off areas acts like a sieve, it lets the water run through, a little bit slower.. but it also catches larger things which in turn makes it bigger. Eventually it breaks down to organic matter and stuff grows on it. Cheap and easy and usually presents itself as an opportunity on it's own, bits collecting naturally.