Don't making it into three total tiers before designing.
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Thanks designshare - I wish we could do what you show - but the septic system is there and we can't do anything abou that. The tiering out will happen in the back corner, starting near the tree line and coming down towards the back corner of the house.

Thanks for the idea though! It would be great to flatten everything out that way!

add a rock azalea retaining wall nice?
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I kinda like the azalea idea... But how will they do under the trees? Are they thirsty enough to handle the drainage from the woods?

azalea like shade.if they thirsty enough,install irrigate system.

Either I can't see your photos all that well or they don't show what I need to know, which is just what your water source and your water destination are. Understanding your water problem is the key here, since it would be a shame to do a bunch of retaining walls and compromise your space with terraces without solving your problem.

Can you do something like a site diagram - even just for yourself, if you don't want to post it - with an indication of where the water is coming from? And where is it supposed to go, if not into your basement? :-) Is there a city drain to which your perimeter drainage should direct it? And what is the condition of your perimeter drainage?

If you can tell us more, then more people may be able to help.

KarinL

The water comes from the hill behind our house. It is non-residential and heavily wooded. Right now, the water is running down that back slope and ends up either in our basement or pooled on our concrete patio, which for some unknown reason tilts towards our house. We want to terrace the steepest parts of the hillside. We are installing French drains to direct water away from the house, and around the retaining wall that borders our driveway (which is what the 3rd photo shows) and out to the drain at the street. Hope that gives you some more info!

Here are some more photos with annotations that might better explain what I'm up against - hope this helps out more than the original photos!

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I'm wondering if you're doing things in the right order here... how did you come to the decision of where the drain should be? Where is it going? and are you changing your existing patio to slope better?

I'm thinking that you should be thinking very comprehensively here, for example, that patio is pretty small. If you are doing a bunch of hardscape, it might make sense to start with the patio.

I'm not the water expert here, but I'm wondering if you might find the water from your terraces is flowing differently from what you are designing your drain for now. So my instinct would be to do the terraces first, though really, it will always be downhill...

As a general guideline, I think you should be putting as much flat area right around the house as you can. Also, I would not use railroad ties. If they are real ones, they are toxic, and if they are fake ones, they look, well, fake :-)

KarinL

Since you aren't getting many responses - not sure why - I thought I would also link you to this old thread with some retaining walls. No discussion of water flow, but at least the visual might help you think yours through. Search the forum for key words like "retaining wall" and you may find others.

KarinL

Here is a link that might be useful: older thread with walls

karin - part of the lack of response may be because we're looking at a pretty complex set of issues here: drainage, steep slopes with all kinds of cross slope, right adjacent to a septic system, and a design brief that really needs teased out and developed. The OP needs boots on the ground. This ain't "what should I plant around my flagpole."

Karin - we are definitely fixing the patio. That thing is the bain of my existence! We haven't decided if it'll be a regrade or if we want to take it up and put a deck area there. It is likely going to be a regrade of concrete though. We hadn't thought about holding off on the French drain system until after we fix the slopes and the patio. But now that the idea has been raised, it makes such perfect sense! We are thinking of having three tiers, and after digging all that out, it will likely make a difference with how much water comes from the woods. I'm now wondering if we just need a drain running along the tree line, and out to the drain at the street. Who knows - it may work out that the tiers and plantings on those tiers, will help enough to skip the drain altogether!

I suspect you will still need your drain in approximately the same location, but if you lay the drain and then wish to lay concrete there, you will be hooped.

The issue is that the same amount of water will come from the woods as now, but it may flow differently after your walls are done, and it may somehow evade your drains or, Marcinde's point being well taken, cause problems with your septic. I would not count on plant absorption of water to accomplish much - partly because it isn't constant, and even if it were it certainly can't surge with water flow. And if your walls do not shift water flow but rather do hold it back, my concern would be that your whole wall and plant assembly would come tumbling down the hill and land on your patio with the weight of retained water.

It is absolutely not impossible for lay people to learn what they need to know to manage a project like this, but the risk arises if you do not take the time to adequately learn it and do something wrong. The risks are anything from doing a lot of work and STILL getting water in the basement, or getting an overwhelmed septic field, or the aforementioned landslide scenario.

Coupled with your slope toward the fence on the other side, you definitely have some grading issues to deal with - I think I would recommend you level the area near the fence with a retaining wall to create a walkable, mowable, plantable area there - and I suspect you would indeed, as Marcinde suggests, be well advised to consult with a landscape or engineering professional who can advise you on the whole scope of the situation and make a grading plan for the whole lot. Then you could either rent or hire the earthmoving machinery to create your new contours, and build your walls from there.

Mind you, with basement water, sometimes the fix is amazingly small, and if it's just to solve that you may not need to terrace at all. We have, for instance, for years had an annual wet-basement-vacuuming event, but were never quite clear on how the water was getting in though we thought it had something to do with the porch foundation. One summer I was mortaring some bricks outside, and I had a little mortar left over, so on a whim I formed a small ledge to direct water away from the door leading into the porch foundation. About a half cup of mortar, the ledge less than an inch high and a foot long - and voila, no more water in basement.

The moral is, analyze your problem first, and THEN design your solution, not the other way around. And don't be embarrassed to hire help for the analyzing, though sometimes, all you need to do is go outside when it's raining hard and be observant.

KarinL