Is this the right idea? Redirecting rainwater

I would love some help to know if I have the right idea or any suggestions to improve on my idea for redirecting some of our rainwater.

Our house is at the top of our property and then the main yard down below. We have a front slope and a side slope and it is the side one I am working on now.

We have one downspout at the end of the house. (Green plastic extension in the top picture) That water is going to a dry creek bed that will take up a lot of the right side of the top picture. Once you get past the downspout the yard goes slightly uphill so the deepest part of the creekbed will be on the right. Right now we have concrete that we removed from the front yard that is stacked on the far right. We will be moving that out a few feet and terracing the side slope.

Bottom picture shows the side slope from the lower part of the yard.

My concern and my idea of a solution follow.

We had a few weeks of rain so the creekbed filled up with water (which was good) and then went down, which was also good. But I need a plan for overflow if we have some extended heavy rain to make sure the water doesn't head toward the house. My thought was to put a pipe a few inches down from the creek bed and send it out to the side slope. Then put a T on the pipe and run a perforated pipe/French drain sort of thing the length of the slope so water could overflow from creekbed in heavy rain and then trickle down the side slope.

Questions I have.

1. Is this a good idea?

2. Is there a better/different idea to explore?

3. Is a French drain overkill for this situation?

4. Anything I should be aware of before we proceed?

Thanks in advance.

Is there a way to put larger water harvesting basins in the yard so the yard can hold more rain before it has to be allowed to leave the property?

http://www.harvestingrainwater.com/

Hi Tyler,
Sorry I was not more clear. The water I am concerned about right now is not leaving the property. My main concern in this situation is wondering if I put an overflow pipe in the creekbed/basin and send it out to a trench with a perforated pipe to the top of the side slope, will that be a concern for erosion at the top of the slope? Maybe I don't even need a perforated pipe? I don't know. Whatever overflow I get, plus rainwater that falls on that slope (which will be terraced) will be all the water that I am sending to that slope for irrigation (once established) It will be planted with natives and herbs for wildlife/pollinators.


The rest of the property (not huge) has a lot of great opportunities to keep the water on site and we are taking advantage of as many of them as we can. The previous owners had dug out two levels of terrace along one side of the property and one of the pictures shows how much water we had in it during one storm. I will be redesigning that so that I capture more of the water higher on the property and the overflows will eventually trickle down to the lowest level rain garden.

Also we have graywater system going in.

And we have 7 more downspouts that will be redirected to the lower part of the property. I am hoping to keep a pond filled with rainwater.

A few pictures.

If you're worried about erosion and just want to get the water away as quickly and safely as possible, a non-perforated buried large diameter pipe may be the best thing. I put a perforated pipe french drain in one area and I don't think it did a thing. Waste of a perfectly useful piece of plastic!

Hey Susan,
Craig Sponholtz is about to be on our campus (April 29) giving a course on water harvesting & erosion control. If there's anyone to best help you with this for a long-term solution I bet it would be him. Here's a link to the course, and best of luck with your yard. What you're going for looks very beautiful! Would love to see more pictures of it Water Harvesting Course

Basics you know. How fast water flows over a given surface, and how deep it flows, determines how much it erodes. Slower and thinner flow = less erosion. Pretty straightforward, but you do want to know how much water how fast _you_ want to plan for at _your_ site.

Maybe you have already figured this, but: What's your maximum local rainfall rate (local records - inches per hour) over a period of time (pick your level of concern)? Multiply by the square feet that drains into your area of concern to approximate the amount of water you deal with each hour. Unfortunately this can get frustrating because engineering tables and records use various different units which need to be converted properly. Tea and Zen time. Then factor in how climate change in your region will affect rainfall events.

I think you're interested in 1) the rate at which water will enter your area of concern (AOC <g>) because this equals the rate at which water _must_ leave through an overflow (how big the overflow pipe must be to handle it); rate "in" also gives you a handle on how quickly your holding areas will fill up. 2) The total amount of water you will have to deal with (duration of rainfall * rate). You already have some clue about how fast standing water percolates but for purposes of quick math and conservative estimates for the "event" you might want to just call it "zero". The rate "in" will also give an idea of whether you need to protect the runoff area (large rock, bricks, etc) so it doesn't wash away, or alternatively, use slotted or holed pipe to spread the runoff over a very large area to that it doesn't erode plain soil. Spreading the flow out slows it down.

Looks like a wonderful project site. Remember to always keep the neighbors happy - don't neglect the social engineering and fences. <G>

Rufus

Tyler, yes, at this particular place, being as the top of the property with the house on it is so small, I want to move the water either by percolating it down in the creekbed or running the overflow down the side slope.

Ellen, thanks for the kind words. I hope you have a fantastic course. Wish it were closer because I would try to attend. I think I need to start a projects page for my various projects.

Rufus, thank you! Yes, you got it. I need to do a bit more math. (My brain, my brain, it hurts!) It is a terrific project site and ideally situated for much of what I want to do with water retention. And yes, social engineering, so important. We have a current "issue" with the one fence we share with a neighbor. We put up a temporary fence while we had the property surveyed. Also because they have a bunch of stuff mounted on OUR side of the fence. So now there is a 3 foot gap for 300 feet between their little fence and our fence and we want our 3 feet for planting. So we need to talk to them about moving their stuff which I am not looking forward to doing. They do not garden, they just pour cement, so it is important to me to claim the rest of our property and plant like crazy.

On the plus side, we have observed the way the water moved in extremely heavy rain when the soil is saturated and none of it overflows to their property.

Susan

Sorry for long delay. Many things going on here.

> talk to them

Do it. Do it now and in a way that there is a clear proven record. This is because "squatting" is an approved legal way to take over property. The below link is a very brief dense intro to the concept. It's relatively easy to draw the lines but it must be done timely and provably and maintained. And of course details vary by jurisdiction so you need to research for your particular locality. This is real.

https://en.wikipedia.org/wiki/Adverse_possession

Lotsa energy to ye.

Rufus

Okay, I think I have a plan which is a good thing since I have a guy with a Bobcat coming in a few days. It will be the last time a piece of heavy machinery will be in the yard. I need the guy to move all the cement stacked in the yard (removed from the upper property and will be used to build retaining walls/terraces on the slopes.) So I figured it he was going to come move the cement so they could build the terraces I could have him save hubby's back and dig me a few holes to catch the water. Rain will hit the yard from a couple of places, I have 6 downspouts on the house that we will run under the deck and out to the yard. The back part of the yard is sloped slightly toward the area where I want to add the rainwater catch basins. I want to do a pond, eventually, but I can't afford to do it now (will have to do the liner thing - no room for critters here.) But since we can't do the pond yet I am debating having the whole dug anyway and just make a very deep raingarden for now then, later, I can take out those plants and do the pond.

What I envision is everything going to the top hole (future pond #1 on picture) first, then overflowing from one to the next, eventually to the lowest level next to the fence. (It used to be a two level terrace but it is all straight lines and doesn't look natural.) That bottom level is flat and flooded very nicely last winter, then it tapers as it gets close to the gate and fence at the bottom of the property. There will be one last rain garden/crater/catchement on the side of the fence before anything can hit the storm drain.

But before I dig all these holes I need to bounce the ideas around and make sure I am not missing something important.

The deepest hole would be the pond one (3 feet? 4? ) Then the next two, maybe 12-18 inches, then 10-12 inches, then anything else can overflower to the lowest level.

While the guy is here I will have him help spread the piles of wood chips so I can start to lay out the greywater plan as well.

Attached are a couple of pictures, one of the space without my crummy markup and another marked up with some basic ideas.

Does it seem like I am heading in the right direction? I will have to decide on the shapes of the holes on the fly since I need the wood chips moved first. I am not sure how deep to make any of these. I need to also site them so the dog still has long, flat spaces to run. Would smaller but deeper catchments work as well or do they need the larger size to better distribute the water?

I hope some of this makes sense. Thanks in advance for any input.

Susan

A bunch of small basins can work as well as large ones and they fit between existing features better. Be sure to put the excavated soil on the downhill side, tamp it down so it won't erode, and have a spillway to the next basin. This might need to be reinforced with rocks if you get erosion, and according to Brad Lancaster is supposed to be 1/3 of the height of the berm, and twice as wide as the berm height. I think your planned basin depth is probably good - my hand-dug basins generally aren't that deep except where I excavate way down to fill with wood.

Make sure the sides of the pond aren't steep in case a critter or person falls in.

Thanks, Tyler. The only way I am going to be able to do these very deep is because we will have the equipment for the day. Otherwise, not so much.

Oh thanks for the information about the spillways. I wasn't sure how deep and wide to make them. I will be reinforcing the spillways and the lower sides of the berms with rocks.

I'm excited since the Bobcat guy said he will be here either this afternoon or tomorrow.