Building a small dam with quikrete

So, here is my idea.  I have a number of narrow valleys that get a lot of spring runoff.  I'm hoping to create some new springs on my land. I am using small swales, brush dams, and the like to try to slow the water high up on the land, in hopes that it will cause springs to form lower.  I'm wondering if I could dig a swale across one of the valleys that is a couple feet into the base of the water run area, and penetrates into the bank a few feet on either side, and then build a small dam by piling in bags of quikrete.  I would stack them like bricks to a height of 4 feet or so above ground level.  Any idea if this will work?  Normally I would just try it, but if this doesn't work, I'll have thousands of pounds of concrete "blocks" to move and find another use for.  Thoughts?

Hi Trace;
Rather than toss down bags. I suggest forming it up as a wall. Use rebar and pound into the ground to help hold it in place.
Form a buttress on either end as well as go into the bank a bit with the wall.  

Lots of questions (mostly for you to think about). I am personally not a fan of small unengineered dams, so this colours my response.  

First... What is downstream of this dam if it were to break? Even a 4' dam breaking can cause an amazing amount of damage if there is enough of a pond behind it.

Second- what are your local laws regarding dam construction, and is this a year round stream? Here a dam like this may require an environmental assessment and most likely a permit.

Are you intending for the dam to overtop or how does the water escape? What are the slopes like (of the valley, and grade of stream, and flow volumes)? What is the foundation soil type?

Why quickcrete? Would it not be easier to just build an earth embankment with a  bit of a spillway? Also, you would want to embed the concrete dam in the ground a foot or two to prevent the water just piping beneath it and eventually toppling it/rapid release of water, and likely would want 2-3 courses of bags in width... this sounds expensive. I also anticipate the bag joints and corners becoming places for frost jacking to eventually break the concrete and ruin it- earth bags with reasonably silty soil (20-30% silt and clay) and some sort of protective cover might be cheaper/less backbreaking and about as water tight.

If you do use quick crete, I would suggest making sure it is in the dry season, so water doesnt wash away the cement in the concrete before it cures (cant remember the technical term for this).

Safest (less prone to breaking due to lower pressures, less risk if break due to less of a pond) and possibly more effective/less time consuming/less material probably would be if you were to make a series of weirs rather than one 4 ft tall dam. A couple 1-2' tall structures would  definitely increase groundwater penetration without some of the risks of a taller structure. Plus, they are less disrupting to habitat and less prone to fill up with silt.

Hey Trace;
Catie, makes some good points.
I especially like her last idea of several  weirs , rather than one taller dam.
The whole idea is to soak as much into your land , rather than let it run off.

Catie George wrote:Lots of questions (mostly for you to think about). I am personally not a fan of small unengineered dams, so this colours my response.  

First... What is downstream of this dam if it were to break? Even a 4' dam breaking can cause an amazing amount of damage if there is enough of a pond behind it.

Second- what are your local laws regarding dam construction, and is this a year round stream? Here a dam like this may require an environmental assessment and most likely a permit.

Are you intending for the dam to overtop or how does the water escape? What are the slopes like (of the valley, and grade of stream, and flow volumes)? What is the foundation soil type?

Why quickcrete? Would it not be easier to just build an earth embankment with a  bit of a spillway? Also, you would want to embed the concrete dam in the ground a foot or two to prevent the water just piping beneath it and eventually toppling it/rapid release of water, and likely would want 2-3 courses of bags in width... this sounds expensive. I also anticipate the bag joints and corners becoming places for frost jacking to eventually break the concrete and ruin it- earth bags with reasonably silty soil (20-30% silt and clay) and some sort of protective cover might be cheaper/less backbreaking and about as water tight.

If you do use quick crete, I would suggest making sure it is in the dry season, so water doesnt wash away the cement in the concrete before it cures (cant remember the technical term for this).

Safest (less prone to breaking due to lower pressures, less risk if break due to less of a pond) and possibly more effective/less time consuming/less material probably would be if you were to make a series of weirs rather than one 4 ft tall dam. A couple 1-2' tall structures would  definitely increase groundwater penetration without some of the risks of a taller structure. Plus, they are less disrupting to habitat and less prone to fill up with silt.

This isn't a stream.  There is no flowing water except in spring from snow melt and during very heavy rains.  It's just a valley on my land that collects water from the ridges on either side.  I'm attempting to sink that water rather than have it run off my land every spring, and ideally, create more springs on my land.  "Downstream" of it is more of the same valley on my land.  

Earth bags are another thought I had for doing this, but they still need to be covered in something or the UV will break the bags down in pretty short order, and bags of quikrete are far faster.  As mentioned in the my first post, the dam will go a couple feet into the ground and a few feet into the banks on either side.  I may just continue with my brush dams for now.

You can see the type of area I'm dealing with here:  Permies thread on my brush dam

I'd stick with the brush dams. They seem to be working well for you so far, and seem a safer and less expensive route to go down. Others have already covered the various risks using concrete.

I have also been contemplating amateur dam building. For my project I was trying to dam the outlet of an existing spring to make it deeper, but decided that for now, I'm settling on a layer of concrete blocks to make a weir. Anyway, one of the things I was going to do for the dam was add a way to drain it, which might help you. I found this slide valve on amazon that receives standard sizes of pvc pipe https://www.amazon.com/gp/product/B000PR50YY/ref=ox_sc_saved_title_8?smid=ATVPDKIKX0DER&psc=1  

So if you do build something deeper I would suggest running a 3 inch pvc pipe under it with a valve on the end so you can drain if/when necessary.

Those gullies look like they may see a fair amount of water during big storms to me. You definitely want to figure out how you plan for the dam to empty once filled, even if it is a very rare occurance. if I recall,  over topping is the most common method of dam failure.

I once saw the result of a catastrophic failure of a beaver dam (which caused a cascade of beaver dam failures), which included moving 6' boulders and scouring out a 6' channel in the hillside, removing 2 old bridge  foundations, and washing out a road, and completely removing an island from a small river. Water is powerful stuff.

I suppose, if I was determined go make a 4' tall dam on my own property, I would probably consider building a 8'-10' wide at the crest homogeneous earth structure, with 2.5h:1V to 3H:1V slopes  with a layer of filter cloth and large gravel to 6" rock covering the upstream side, and a spillway made of a concrete channel drain (long piece of concrete with 2 raised sides) about 1 ft lower than the crest and more filter cloth and rock to protect the downstream slope below the spillway. Or a lined rock fill dam, with liner on the upstream face trenched in at top and bottom. Good liner with UV protectants should have a 20-100 year lifespan.  This is not engineering advice, I have never seen the site, no idea about seismicity, soil types, rainfall, catchment, etc,etc, but these are the dam types I have seen be both relatively easy to build and long term successful.

If you used earth bags, you could cover with gravel.

Seriously though,  I would have nightmares about dam failure and liability. I have spent far too much time swearing about previous small dam builders to be comfortable with them. IMO half assing a dam is rather like half assing electrical systems. Either you regret it, or the next person regrets it.

Oh- and if you decide to build a concrete dam, it doesnt work, and you decide to later build an earth embankment, make sure to take the concrete out before you build the earth embankment, as the concrete will likely make the earth dam more likely to fail.

Catie George wrote:Those gullies look like they may see a fair amount of water during big storms to me. You definitely want to figure out how you plan for the dam to empty once filled, even if it is a very rare occurance. if I recall,  over topping is the most common method of dam failure.

I once saw the result of a catastrophic failure of a beaver dam (which caused a cascade of beaver dam failures), which included moving 6' boulders and scouring out a 6' channel in the hillside, removing 2 old bridge  foundations, and washing out a road, and completely removing an island from a small river. Water is powerful stuff.

I suppose, if I was determined go make a 4' tall dam on my own property, I would probably consider building a 8'-10' wide at the crest homogeneous earth structure, with 2.5h:1V to 3H:1V slopes  with a layer of filter cloth and large gravel to 6" rock covering the upstream side, and a spillway made of a concrete channel drain (long piece of concrete with 2 raised sides) about 1 ft lower than the crest and more filter cloth and rock to protect the downstream slope below the spillway. Or a lined rock fill dam, with liner on the upstream face trenched in at top and bottom. Good liner with UV protectants should have a 20-100 year lifespan.  This is not engineering advice, I have never seen the site, no idea about seismicity, soil types, rainfall, catchment, etc,etc, but these are the dam types I have seen be both relatively easy to build and long term successful.

If you used earth bags, you could cover with gravel.

Seriously though,  I would have nightmares about dam failure and liability. I have spent far too much time swearing about previous small dam builders to be comfortable with them. IMO half assing a dam is rather like half assing electrical systems. Either you regret it, or the next person regrets it.

Oh- and if you decide to build a concrete dam, it doesnt work, and you decide to later build an earth embankment, make sure to take the concrete out before you build the earth embankment, as the concrete will likely make the earth dam more likely to fail.

I appreciate the concern, but I think you are vastly over-estimating the amount of water I get coming through here.  Either way, I may just stick with my brush dams for now.

I'm not sure what your brush dams entail, so apologies if this is redundant. My understanding is you want to not CONTAIN the water, but slow it enough so that it is absorbed by your land and does not rush by and disappear during the wet season.

For me, I must concur with everything Catie has said; continuation of brush dams is simple, inexpensive and contain little to no risk. The "HOW" of the brush dam is the question.

I would utilize the "brush fence" technique: impale pruned or salvaged branches across the valley low spots, say every 2-6 inches, and place other brush, leaf litter, garden waste, used straw, used hay, what have you in front of the impaled sticks.

Your goal is to slow not contain the water. Depending on length of valley, this could be repeated multiple times and over time, with added materials, could gradually become berms, swales, terraces or hugel mounds.

In a perfect world, moldy or spoiled bales of hay or straw would be the ideal medium for this, and the branches can be stabbed through the bales to anchor them.

Save your money, energy, and liability, stick to stuff that impedes, not stops flow, and will naturally break down over time.

Trace

I'm the cautious type, but that's been covered pretty directly... <g>

What I want to mention, on the off chance you haven't checked your local authorities lately, is that I hear more and more reports of counties using satellite images, drones and/or payed low level photo planes to "survey" their territory. Bureaucracy is dipping it's toe in the 21st century. They're looking for taxable, fee-able, or actionable site changes to help keep their paychecks coming. These days, it looks like a good idea to "manage" your relationship with officialdom, rather than leaving it to chance and distance. The latter doesn't work so well any more, what with cheap tech and everybody's budgets evaporating.


Regards,
Rufus

I would build a series of weirs, all low and hope each weir fills with soil and then build them up again.

And I would use those bags you spoke of that are going hard, they will have no difference to the environment than concrete would.
And many use concrete.

It could be called soil conservation.
It iust something I spent time with doing in Australia.
By slowing the water down, you can entrap it and then continue the process.
I doubt anybody will get upset over that.

My most successful checkdams were the smallest. A single layer of rocks or logs. Then after that filled with sediment, adding another layer of rocks or logs on top of it. Building them up gradually over a number of years...  

The 4 feet tall checkdams that I built washed away in the first storm. The small ones remained behind, filled with sediment. Bedrock was common at my place. I would have poured concrete onto the bedrock and embedded rocks into it if I had been able to visit the land more often. Separating "blocks" of concrete with paper/plastic doesn't seem structurally sound to me. I would mix and pour.