If rain falls in the area, which way does it drain, fore or aft? Does it drain well, or puddle? Does water flow AWAY FROM THE HOUSE all along the concrete slab? Is there a "gutter" at the top, back of the new wall that carries water fore or aft ... or will all water drain over the top and face of the wall? From above (behind the fence) is there much more area that is draining down the slope, or is it primarily the slope we see only? Is the topography outside of the fence at a lower elevation such that an underground pipe could exit without running it a ridiculous distance? I would forget about any idea of a french drain BELOW the patio. This would not be good for its stability, or be a good solution for a number of reasons.

If you have a yard out back that slopes away from the patio, consider installing dry well(s) to carry the water away and dump it in the back yard at an elevation that is lower than the patio. Scout you problem area and decide where you want to place the collection well(s). You could create a minor depression that is lower than the surroundings. What I propose does require some digging. Basically, a dry well will be buried flush to the ground, water will run into it, and near the bottom of this well, a drainage tube will be attached, laid in a ditch which has some pitch toward the back. Carry this ditch back until it is exits at lawn level. I used a plastic sump well. It is easily cut with hand tools and is low cost. Near the bottom of the well, cut a hole to receive the drain pipe (tubing). This should be a snug fit, but does not have to be water tight. I used standard thin wall drain tubing, but a littlier heavier wall is recommended to guard against collasping. However, I have a 25 yr success with my thin wall. Various fittings are available for the tubing, for example, a Y connector. I plumbed 2 wells together using a Y-connector and then drained both wells out a single pipe. Its ok to let the drain tubing extend a bit into the dry well, say 2 to 3 inches. Once everything is in place a test made to insure that it will drain properly, back fill the ditch and around the dry well. Fill the dry well with fist sized stone for the first 2/3 of depth. We want to create a permeable filter that will support your weight if you step on it, and to keep debris out of the drainage system. Full the top layer with smaller stones until flush with the top of the well. Over time, leaves, sticks, and other stuff may collect on top of the stone fill. Periodically, brush this stuff away. Any small particles that get through the filter will flush on out the tubing. This well will accept a good flow rate and remain clog free for many years. You will need to pay attention to the exit end of the drain tube. Here, it is desireable to spread the stream to slow it down and to counter errosion. If you can establish a good sod layer for the exit, that may be all you need to do. Otherwise, you may need to provide a gravel bed to spread the streasm. If the slope is steep at the exit end of the drain, install some flat rocks to create a tumbling water fall and stream spreader. The hardest part of this project is digging the ditch in which to lay the drain pipe. My soil contained 30% glacial till and that was tough - keep finding stones. To cut down the labor, I used a garden roto-tiller to cut the ditch. I unbolted the outer tines so the the cut width was no wider than the machine. I used the tiller to loosen the soil and I periodically shoveled the loosed soil to one side of the ditch. I carefully piled the dirt in a compact ridge near the edge of the ditch because it was going back into the ditch and it was desired to minimize effort. Mine was an old fashioned tiller with the tines running at slow speed. If one of the tines hit a rock, it merely lifted the machine without breaking any thing. My ditch was 3 ft deep at the dry well. Your installation can be more shallow if you are in a low frost depth zone. You can adjust the well depth by cutting off its top. having the drain pipe buried at least 12 to 18 inches deep tends to hide it presence in very dry weather. In dry weather, grass may brown out sooner above the pipe where it is shallow.

Thanks for the answers. Yes, the water does flow naturally downhill, but since it comes from one specific part of my northern neighbor's yard it has created/eroded a large section going down the hill. I'm trying to keep the hill intact and limit the flow and erosion as much as possible. I added the tile pipe to control the flow of water as it enters the yard from my fence line. It has done of a good job of catching water and keeping it moving more narrowly through a couple of heavy rains, but the initial moving of the dirt caused problems a the low spot. I thought I could eventually cover the pipe with dirt over time even if I can't grow anything on the pipeline (ie grass) the hill will stay together and look even, which is really my only goal. The creekbed at the bottom of the hill will be a natural barrier between the rest of my yard (flat) and the hill up top. I see what both suggestions mean by finding some larger, more suitable plants for ground cover. The hill pipe flows naturally into the dry creek bed that is now covered in rock. It sounds like the pipe down the hill may not be answer and I may be planting something with deeper roots along the hill where water flow. Thanks again for the responses.

In my opinion you do not need to spend a lot, but can resolve the problem by re contouring those areas so the drain. When you re-contour make sure that the problem areas have a clear sloping path. Water will always go down hill. I have a similar problem in the yard in the corner of my patio and house. The problem is caused by a ridge of hard clay the was dug out out of the patio area when it was put in. The clay creates a dam across the drainage swale from that corner. When they did the final grading after it was installed, they did not consider the type of dirt. My solution is to dig a shallow channel across the clay to create a natural looking swale so the area can drain. The new swale is only about 5 inches lower that the surrounding yard and is shaped so the lawn mower does not notice the swale as in moves across it.. Both of the areas in the Picture "Back yard", could be corrected in this way by remove the sod and making the wet spot part of the drainage channel. Dig deeper so when you replace the sod the areas will drain. Similarly in the next three pictures. In the last picture I am not sure what I am seeing. but it looks like the nature drainage channel goes into a culvert under the road. If so this problem started decades a go when the tree was planted in the original drainage ditch beside the road, It may be only solved by removing the tree, but that would be costly, to cut down the tree, remove the roots, and regrade.. Before I took drastic measures I would dig out the years of accumulated leaves (now soil) so the water has free access to the culvert. I may also use that material to create a dam by filling the are to the right (Picture) of the forked tree forcing the water between the road and the tree. Just adding the dirt to the wet area may be enough. I would have to sit out there studying the area before making a decision on how to proceed. In my estimation this is the only area where you may need to spent money to correct problem. My "amateur advice" ;-)