Design ideas: French drain + back gate access

mj_frederickJanuary 25, 2012

Hi everyone! I have a landscape dilemma for which I need some suggestions.

I live in a townhouse middle unit, with slightly higher ground on the left and slightly lower in the right. When it rains heavily, my French drain fills with water, sometimes slightly flooding my cement patio (but not getting all the way to the house). This convinces me that I need to keep the French drain (thoughts?)

The main part of my yard has tree bark mulch for ground cover, filled with two very large trees and some shrubbery. It is mostly for looks as it is sloped. My dog also uses it to explore and go potty (which knocks the mulch to fall into the French drain).

Also, right now to get to the back gate (at back left) we have to walk through the French drain and uphill on the mulch, which is awkward. I would love to install some pavers on the mulch part of the yard but I am afraid they would just sink into the ground, and plus that would not solve walking through the French drain.

Does anyone have some suggestions that would enable me to:

1. Keep the French drain (or something that works similarly)

2. Have easy access to the back gate

3. Make this yard look better!

Here is a link that might be useful: Pictures of backyard

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Is the thing you're calling a french drain the light colored gravel covered area? French drains are typically buried perforated pipes that collect stormwater to convey to other parts of the property. If you have a french drain there, it may not be installed properly or it may not actually convey water away from the area.

Once you have a properly installed and protected drain, you can put pavers or whatever over it to make it look more connected.

    Bookmark   January 25, 2012 at 2:02PM
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Thank you tanowicki! This is helpful. Yes, the previous owners called it a French drain but really it is just a 2-foot thick line of small rocks running across the low point of my yard. Water tends to gather there when it drains and then run off to the right (onto my neighbor's property). So if I'm interpreting your message correctly, you think the right thing to do is dig out the rocks, install a real French drain, and then put whatever we want on top of it? Would this route a lot more water onto my neighbors'? The flow to the right is pretty gradual now.

    Bookmark   January 27, 2012 at 9:56AM
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What I see in the photos and text indicates a surface drainage problem. French drains are inappropriate for excess surface water. If I had a contractor even mention a french drain after seeing the this property, I would escort him off the property and tell to not come back.

This looks to be a difficult problem to solve. The controlling element will be the ground elevation where water leaves your property and flows onto your neighbor's. Without an accurate comparison of the elevation at that location with the grades throughout the backyard, it's unlikely that you will get any meaningful help from this forum. What is needed to assess the situation is a scaled base map of the property with accurate elevations.

    Bookmark   January 27, 2012 at 11:49AM
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I agree with pls8xx that an actual french drain will not solve your problem. Unless you have something to tie the drain into, it will just sit in the drain waiting for somewhere to go. It may get it below the ground level but then the area would be soggy below ground instead of at the surface.

If the neighbor's yard is lower, is there an impediment to the water draining there? Like a fence or some kind of border on your side?

    Bookmark   January 27, 2012 at 12:28PM
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Not only is it unbelievably rude to drain water onto your neighbour's property, I believe that it is against code in most areas.

    Bookmark   January 27, 2012 at 2:43PM
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I tried to figure out how to state that she/he should be careful while doing this but what is the difference if the surface water drains to the neighbor's property now? If I had a puddle that formed at my fence every time it rained because I had put up a horseshoe backstop and the water took longer to go around it, would it be in poor form to move the backstop so that it didn't block the runoff?

If I were to pave my entire yard so that no water could infiltrate and funnel all the roof discharge plus new paved area into my neighbor's yard, they would have an issue.

    Bookmark   January 27, 2012 at 2:56PM
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deviant-deziner(Oh zone)

There are a couple of ways to address this problem.
The solution will depend on your budget , your condo association, local code compliance and final design direction.
For those reasons above , it is usually a good idea to have a professional working with you to help you through the various channels and provide you with a cost analysis and budget projection.

Some of the options that you may or maynot have available to you are :
1. Explore the depth of the seep . It may be able to be expanded to handle the disipation of the run off . In cases like this ( usually larger ) I work with a soils and or a drainage engineer.

2. Work with your condo assc. They are usually responsible for your drainage.

3. They , the condo assc. may opt to install a perforated pipe connected to a tight line to move the water off of the property and to a city sewer system.

below are some photos of some larger properties that shared the same issues as yours.
below: a land locked property sitting at the bottom of a valley- no storm water drain to connect to. An point of refusal drain system of several feet deep was engineered under the gravel paths.
From California Gardening From portfolioMay08.jpg

same garden as above showing the drain channel

Photos above : Property took on all of the neighbors sheet flow storm water run -off . A dry stream bed was engineered that was part seep and part perf / tight line connect to a open culvert system . A dry stream bed dresses up the drainage channel.

Below is a photo of a back yard in a condo complex. After finding that the yard was not draining properly the complex dropped in a tight line system and left the tiny 20x20 back yard with a 3'x3' concrete and steel grate drain inlet (over kill ) . We designed a core ten planter to cover the drain inlet .

    Bookmark   January 27, 2012 at 4:03PM
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MJ, coming to the conversation a little late, but as I see it, your photos do not adequately explain the conditions. Terminology is a little loose in the landscape industry and there's disagreement from one geographical area to the next. Because your rocks are at the surface, I would call them a "dry river bed." If the same was buried but had an inlet, I'd call it a "french drain." Unlike sewer drainage systems--which can, theoretically, hold unlimited amounts of water as the water keeps on flowing--french drains are self-contained, having a finite capacity created by the voids between the stones in them (and pipes, if any) with all of the water eventually seeping into the ground in their vicinity. French drains may contain perforated pipes to hold even more water and distribute it faster, but they do not connect up with other drainage systems (such as a sewer.)

It is normal for water to be draining downhill from one property to the next. But one just can't "funnel" it and cause problems or damage. Your pictures do not tell the story because they do not show THE PATH where the water needs to go. Somewhere in this path, there is an impediment to the flow. Can you post more that show this? (It's a lot better, too, if you paste the html code (for the picture) directly into your message so we don't have to leave the page and forum comments to see it.)

    Bookmark   January 27, 2012 at 4:21PM
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karinl(BC Z8)

Agree with embedding the pictures - that's a really troublesome site to load. One question you can also ask is whether, with your condo association, you can discuss something to do on the uphill property to stop so much water coming from there.

Karin L

    Bookmark   January 28, 2012 at 1:15AM
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A french drain simply will not work as the velocity is to slow. Removal of the rock and install a trench drain ( a trench lined with brick concrete plastic , or other material) with a grate. The side walk can have a solid area if you don't like the grate where you walk. Many prefabricated trench drain products are available.

Here is a link that might be useful: Trench drain

    Bookmark   January 28, 2012 at 7:15AM
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Thank you everyone for these replies! I believe Yardvaark is right and my situation can better be described as a "dry river bed" than a French drain.

I am adding a diagram to the website. I don't know how to embed pictures...?

Some notes to reply to other's posts:

1. Our three yards are on a very slight downhill slope from left to right, so it looks flat until there's a heavy rain, you can see the water going from left to right. This was the design of our backyards - my neighbor to the left is not being flooded, it passes through his property and out to a storm drain.

2. The neighbors to the left have a water pump on the left of our 3-unit building so most of the water doesn't flow across our three units - so the flooding is minimal and occasional (before the pump it was awful and I am still a little afraid of that thing going out).

3. The "dry gravel bed" is actually working well, the problem is that it cuts horizontally across my yard and there is no path to the back fence without walking through it - cumbersome as it is rocks.

Maybe I can do something with absorbent plants, or maybe expand the dry river bed out to the fence and get smaller (more foot-friendly) rocks?

Thank you again for all the comments! I am very new to landscaping and just want a way to reorganize the backyard so that it "flows". (Sorry for pun.)

Here is a link that might be useful: New diagram + Same pics

    Bookmark   January 30, 2012 at 3:37PM
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If it's just a way of getting over the dry stream bed, why not put in stepping stones or even a little bridge? So long as what you put in doesn't dam up the bed, it should work.

That slide show thing is horrid for looking at pictures.

    Bookmark   January 30, 2012 at 3:59PM
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Drainage to this property needs two considerations:

1.Risk of flooding to the townhouse from large storm events

2. A plan for the nuisance water from more common storms

From the first post, it appears the property is in Georgia. Across the southeast US, typical 100 year storms include 9 to 12 inches of rainfall. It's not uncommon to see flows that are 50 times greater than that of a 1 inch rain. Few people understand this because they have never experienced such a storm.

To assess the drainage here, one must look well beyond the bounds of the property. Subsurface drainage facilities are almost never sized to deal with major storm events. Thus most water flows are dictated by surface topography. The location of the pump on your left neighbor's property suggests that there is a continued up-slope and water not handled by the pump may continue across your property. When the big storm comes, it wont matter if the pump runs or not, it wont pump enough water to matter.

Photos are nice, but it will take both horizontal and vertical measurements to understand, predict, and plan for the flows. I caution you that a ill advised plan to deal with the nuisance water might well be an obstruction to the flows of a major event, causing your townhouse to be flooded.

A homeowner can be guided to take the needed measurements, but it is a lot of work. The crude drawing is a start to the scaled base map needed. For those who might be having a problem with the slideshow, I'll post a copy ...

    Bookmark   January 30, 2012 at 5:14PM
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I still don't see a series of pictures that, to the best of your ability, show the path of where the water is going when it leaves your property. I almost see a picture of the right portion of your dry river bed. Then, I see nothing beyond... how it enters the neighbor's property to the it flows through, and how it leaves his property and what's next. Does neighbor to right have same problem? Position the camera so as to reveal the grade, if possible. Guess what... if it's dammed up anywhere along that path--intentionally or inadvertently--the water's going to back up. We need to see the path.

To imbed pictures here, on another tab/window, go to the picture where it's hosted. Look for the word "share" or maybe at your site they call it something else, but similar. Explore around a little until you find a way to get the html code for the picture. Copy it. Go back to GardenWeb where you are creating your message. Paste the html code for the picture into the message. Go back to your photo-hosting site and get the code for any other pictures you're including and paste in GW by the same process. Click on "preview message" and you'll see that if you grabbed the right code, the picture will show up in the preview. One site I use has MANY options for different codes for each picture (depending on the size you want) so it may take a little trial and error, but you'll find it.

Based on your diagram (and thank you, pls8xx, for posting it here) I think I understand the general concept of your dilemma... but not at all the details that are necessary to put the puzzle together... or to know if it CAN be put together via forum. Need to see the path of drainage.

One thing I'll say that appears not right from your photos: the gravel looks to be at a slightly higher elevation than the patio surface. It seems that for a device like this dry river bed, it should be lower than the patio, creating a "trough" of sorts as a channel to carry the water away before the water gets up onto the patio. If it's higher than the patio (since water doesn't flow uphill) it's making the patio (the lower elevation) become the trough to carry water. Please confirm which surface is higher, relative to the other. If the patio is lower, the solution would be to remove soil from below the dry river bed and lower it's elevation, so that the patio was at an elevation above it. BUT THIS COULD NOT BE DONE BEFORE KNOWING WHAT'S BEYOND or you stand a fantastic chance of making the situation dramatically worse! Did I mention we need to see that drainage path?

    Bookmark   January 30, 2012 at 6:25PM
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