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Designing a streambed for roof runoff

Helena, MT(Zone 4b)

I bought a copper rain chain to replace one of our downspouts, and hung it on a corner where the ground slopes down through a narrow (12') area between our garage and fence. Now I'd like to put in a water feature, but not your traditional pond. I envision a runoff channel that would be dry most of the time, but it would be like a mini-stream when rainwater is pouring off the roof. I want to direct the water down toward our neighbors' enormous spruce, about 25' away.

Can anyone give me any design ideas or practical tips on how to do this? Do I simply dig a ditch and throw in some pretty rocks? Or does it need a liner (old tires or something)? How would I make a little cascade? Keep in mind that the only time it rains very much is May-June. We get 11-12" of precip a year, which makes this a mountain desert.

Dublin, CA(Zone 9a)

My first caution would be to not direct the water toward your neighbor's yard, you can get in trouble for doing that. Maybe the rules are different in Montana, but in most places you're not allowed to do anything that directs water onto your neighbor's property. Given your general lack of rain, maybe this isn't a big deal but it's something to consider.

If you look in my diary, you'll see an example of a dry creekbed that flows down my front hill--it's basically a ditch with some pretty rocks. If you want to keep the weeds down, you may want to line it with landscape fabric too. As far as creating a cascade, that may be hard depending on how much elevation difference you're talking--if the slope's not that big then you probably won't be able to do something like that. And since you don't get a lot of rain, I don't know how much of a cascade you'd ever see, so it's probably not worth the effort. We get more rain than you do, and I have never seen water flowing in my dry creekbed even though the grade is really steep and there's a decent amount of water draining into it. Occasionally a little trickle, but that's about it, nothing that remotely resembles a cascade! I suppose if you lined your creek with plastic or something that won't let water drain through then you'll see a bit more water flowing, but then you'll run more risk of getting in trouble for dumping water on your neighbor's yard too and I still don't think you'll get the cascade effect you're interested in.

You want to be careful with this because a big rain could destroy all of your hard work. One big storm and the force of the water could move all your stones down the hill.

Treat the channel as if it has been there for years...dig it deep. You probably need to go down between 6" and 12". You can make the channel different widths at various points to give it more dimension. Line the channel with landscape fabric. Weeds really are not the issue. Without fabric water would flow down the channel and mix the soil beneath with the stones above creating a future muddy mess. The fabric stops this from occurring. Also, you will eventually get weeds in your stream bed no matter what you do. Next, use a combination of 4" to 12" stones to line the edge of your channel. This will hold everything in place. In the middle of the channel use 3/4" to 2" stone from the area. To get a visual movement of water in the channel you can put a few 4" or 6" stones at various points. At the end by the Spruce you can widen out the channel at least 2-4' wide so that the water disperses over the area and doesn't flow directly into the neighbors yard.

If you want to see more water in your channel then use rubber liner (like pond liner) for the first 15' and definitively use landscape fabric the last 10'. Remember this...the water coming down from the rain chain needs to be diverted away from the house or you could end up with major water issues. No matter what use at least 5' of rubber liner starting at the house so the water won't start working it's way into the soil next to your foundation.

I will draw you something of an idea and post it.

Not my better work (or to scale), but it works. That'll be $250.00...just kidding! I crack my self up. :)-

Forgot the picture.

Thumbnail by shrubbs
Novato, CA

Do not direct your properties water run off to your neighbors yard. Period.
Unless you welcome a lawsuit.

In this area we have to divert the water to based on the terrain. In one instance our client's yard was the swale for everyone else's watershed. Because of the terrain in our area it is sometimes impossible not too. As long as the channel ends a good distance from the property line and the water is allowed to disperse into the yard you should be okay. If you think about it...your water is already being channeled to the neighbor's property on the side of the garage. As long as there is a swale on the property line and you don't channel the water directly to a specific point at the property line you should be okay. Talk to the local county office for the codes and guidelines that apply in your area.

What I would consider is buying a 500 gallon cistern, install it underground, and run all of your downspouts to it. You can collect all of the water and use it in times of need for your plant material or washing the car. Even in this situation excess water from a overflowing cistern will need to be diverted somewhere else. In the end it could run between $1,000.00 and $2,500.00, but it will be well worth it. No water bills for plants.

Novato, CA

I live in California so this may be why I have a different working opinion with the process that shrubbs has suggested.
_ You cannot direct surface runoff from your property onto your neighbors.
If native terrain naturally falls towards your neighbors side that is one acceptable drainage diversion, but you cannot create a man made drainage ditch and direct water off of your property to your neighbors property.
If there is a grading problem caused by a developer that drains your property water onto your neighbors by law either the homeowner or the developer must take code compliant drainage steps approved by your city or county building and planning dept.

_ By law / code, the drainage plan that shows the stream bed angled directly at the neighboring spruce tree , which is not on your property, would constitute legal action. It is not in code compliance and it also would not pass acceptance from any licensed arborist.
If the spruce tree dies due to excessive water / root rot, you the homeowner would be responsible for all damages, including the cost for a consulting arborist , removal, replacement and surrounding property damage , if any, while the tree was removed and replaced.

_ Last time we installed a cistern or an underground rain collection vault with a pump so that you could pump out the water and use it for summer time irrigation , the cost was over 5,000.00.
This system is really only cost effective if you have adequate rainfall for collection and then redistribution.
Data is available to run your calculations at your county ag or water agency.
In my area I contact the water department for their calculation in order to engineer the correct size vault and pump size in correlation to the amount of average rainfall.

If you live in a mountain desert this may not be a cost efficient option for you.

California sure is different than Central PA. I originally came from Central NJ (near Philly), but these things were never such an issue. Everyone's water went to the property line because of space and elevations. But...I can understand the issues that could arise in this area should you have sue happy neighbor who's only concerned with what they can get. It's pretty cool seeing how different areas tackle the same situation. I did forget to mention about the potential major root rot problems with the Spruce. Thinking it and writing it are two different things. :) As for the cisterns...I would still recommend one no matter how much rain an area might get. People have been installing them in our area for the past 2 years because of the below average rainfall. Any means of water will help.

Dublin, CA(Zone 9a)

I imagine the majority of places have some sort of rules about purposely routing water onto your neighbor's property, I really don't think it's just a California thing. This has come up on other threads before and others have had similar rules in their area. If you live in a hilly area, nobody gets held responsible for water draining naturally from higher to lower areas, but if you install something that changes how water drains so that it's directed onto your neighbor's property, I think you're going to get in trouble for that in most places. When you talk about everyone's water going to the property line, that's different, there it sounds to me like everyone's yard is graded so there's a low point betwen the two properties, and both properties drain towards that low point? You could certainly build a subdivision that way in California too and it wouldn't cause a problem, that's not the same as routing your drainage onto your neighbor's land.

Helena, MT(Zone 4b)

Wow, thanks, everybody! What fun, I even got a drawing! I'll definitely use the suggestions about lining the trench. 6 to 12 inches deep sounds about right. But I do think there will be a good flow, ecrane, simply because it's coming off the roof, and we have spring storms where it pours off at an impressive rate.

Yes, shrubbs, one of the purposes is to divert water away from the house, as this slope follows the back wall of the garage. I also like the water collection idea. It takes a lot of watering to keep things alive here in the hot, dry summers.

Thanks for the warnings on legal issues; now you can all stop worrying about that one. The spruce is right next to the property line, and we have loads of roots on our side that we can water. Besides, these neighbors would simply tell me to get my runoff off their property if that's the way they felt about it. We'll no doubt have a few discussions on the project before I get going, because Rich & I like to trade garden ideas.

Dublin, CA(Zone 9a)

Regardless of whether you and your neighbor can agree on things, I'd check into what the rules are in your area. Your neighbors may not live there forever, and the next people could get you in trouble over it if it is against the rules.

Helena, MT(Zone 4b)

I'm not planning on directing any water to their property, ecrane. I've got plenty of spruce roots to water over here on my side. Not to worry.

Fredericksburg, VA(Zone 7b)

You might try a rain garden..I included a couple of excellent sites with more information in this article.

Minneapolis, MN(Zone 4b)

The rain garden is a great idea.

Helena, MT(Zone 4b)

doccat, that is exactly what I want! I didn't know what it was called.

I need the runoff channel to get the water away from the garage foundation, and the spruce happens to be downhill. What I have planted there now is sweet woodruff, but I can always add some things by creating a bigger "sunken" area. I just need to keep the apricot trees high and dry, as they do not like excess water. The big challenges are 1) our drainage isn't the greatest (moderately clayey soil) and 2) everything dries out in mid-July for a long long time. (October? September? Who knows when it'll ever rain again?)

Fredericksburg, VA(Zone 7b)

I'm glad to hear that. Do google the web for additional information. I just encountered this idea in my Master Gardening classes last year. I've been workng with one of the more experienced MGs on developing a plan for one of these at one of the local historical sites. It's fascinating. Good luck to you! Please provide pictures of the progress, that would very interesting. Thanks

Minneapolis, MN(Zone 4b)

Rain gardens use native plants so you need to be looking for the plants from your area that live in the climate you experience. We put in a modified rain garden a few years ago after taking a free class given by our city. The first link here is for Montana, the second for Wisconsin which is the best one I have seen. I only googled the one for Montana I didn't read it.





Fredericksburg, VA(Zone 7b)

The VA site will lead you to some of the better sites as well. Some of the best are in Maryland. Interesting stuff.

Helena, MT(Zone 4b)

Thanks for the links, everybody. I can already see what the main challenge is going to be: clay soil that doesn't drain all that well. I suppose I'll have to improve the drainage somehow. I don't know if there are any plants that tolerate poor drainage and conditions going from soggy to drought! And alkaline soil on top of that.

Any input from the plant selection experts?

Fredericksburg, VA(Zone 7b)

That's why your native plants are recommended . They are tough and do tolerated lousy soil and drainage conditions. They are already adapted to your local conditions, climatic and otherwise.They will act as the "filter" for the drainage and many have root systems that will break up the clay with little problem. They're job is to act like a giant sponge/filter system. Check with your local extension agent about what types of native plants are best in your area. Also see if he can hook you up with some Master Gardeners in your area. Something like this would be a great project to help with.

Minneapolis, MN(Zone 4b)

I found this site for MT native plants.


Helena, MT(Zone 4b)

That makes good sense, doccat, although many of our native plants are very rock-garden-like in their drainage requirements (Pasque flower). It's probably a no-brainer, though: look at what grows in areas that get soggy in the spring (Marsh marigolds, willows). I also have a friend who is a member of the Native Plant Society (the link you just posted, zenpotter).

Fredericksburg, VA(Zone 7b)

Yeah! zen is ma girl too!

Minneapolis, MN(Zone 4b)

I am a total believer in native plants.

Fredericksburg, VA(Zone 7b)

It's all those varieties of "icicle and snow baby plants that are native to MN"...........grin

Minneapolis, MN(Zone 4b)

You forgot the ice crystal plants. They make good ground cover. Actually there are a few green plants here on the tundra.

Now this is the honest truth. We have two native cactus plants both Opuntia.

Fredericksburg, VA(Zone 7b)

I went to college in Minneapolis for 5 years, I understand! LOL

Minneapolis, MN(Zone 4b)

Which college?

This isn't the best place to garden that I have lived, but it sure is great for artists.

Fredericksburg, VA(Zone 7b)

I went to the Northwestern College of Chiropractic, which is now located in St. Paul. Much larger school with nicer facilities. But it was great fun and a wonderful experience. I was the only woman there until my last year. And the guys were great. I am an "honorary" member of the fraternity, the guys went all the way to the state chapter to get that set up for me. The sweeties.

Minneapolis, MN(Zone 4b)

What a fun place that must have been.

Fredericksburg, VA(Zone 7b)

It was, I had a wonderful time and did a lot of "growing up" in that environment. I was very shy of guys when I first got there, I got over that in a hurry! And after about 3 months of blushing regularly at some of the material, I got over that too. I was very lucky, I talked to other women going to some of the other colleges and some of them had a very rough time of it. My guys wouldn't tolerate that stuff, had a few creepers but usually a word or two in a couple of ears took care of that. Some of these guys were big dudes. LOL

Minneapolis, MN(Zone 4b)

You were lucky.

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