Since the walls are concrete, I assume you are in a mild climate where deep footers are not needed. And the top of the retaining wall at the rear of your property is higher than the top of the sloped wall at the NE property corner, If you look up the sloped wall from the NE corner, at the top the soil grade falls against the wall. down the slope the soil grade is near the top of the wall, At the NE property corner the yard grade is somewhat higher than the top of the sloped wall. The above being shown in profile on the left side of the graphic below. I suggest you build another short concrete wall about a foot inside the sloped wall as shown above. Dogleg the end at the rear wall to allow a place for yard water to flow to the corner. The area between the walls should be concrete to carry any water flows without erosion. If the maximum height of the new wall is 16 inches, it's a reasonable DIY project.

"Posted by matt_m (My Page) on Sat, Jun 8, 13 at 0:11 I really appreciate all of the advice. We are situated on a hill, near the top -- in 10 years, flooding has never been an issue, but it has with people who live further down the road." Engineering is an exact science, based upon assumptions, and in that light an engineer is required to provide a design that budgets for and meets the minimum design criteria for the area in which you reside. IE., overturning moment; at heights over 6', wind governs, so the design will budget for the installation of privacy slates or removal of the fence fabric and wood panel placed between the steel posts, which is a common design alternative. "(one an engineer at Sunroc)" I would urge you to seek the advice of a private professional civil engineer. " the winning idea is a 8" - 10" deep footing, 12" to 16" inches wide, with a 6" block wall or concrete wall on top of that, centered on the footing, with rebar uprights every three or four feet, as well as at least two bars the length of the footing and at least one bar lengthwise in the wall." With the exception of the 2nd piece of rebar in the footing, this is a typical "garden wall", not a retaining wall. Generally speaking, a wall less than 2'6" in height "is not" considered to be retaining. No soil added around the trees! Just running the wall in a straight line down the property line. "putting the posts directly in the wall" Which would be ok, except that you have something called "cost", which is the required embedment of rebar in masonry walls, which is 2" and cannot be attained using 6" block. "I might as well pour a concrete wall!" Not hardly! "One thought I had was this -- if I build the wall on my neighbor's side of the property line (he doesn't seem to care one way or the other, especially since I'm doing all the work and paying for it), is it then his wall?" If you are, indeed, contemplating this, you need to obtain and easement based upon the final wall design, because if you take a "disney land" approach to this, if you have a lender for you property, you'll find them defending ONLY their intreats and NOT YOU. There are prescribed and restricted "drain fields" which are designed to protect "downstream" home/properties from from natural occurring moisture from affecting that habitability. Those exist in your case and must be addressed. It's called "hydrology", and will be addressed by an engineer. "Not sure about how that would affect things." You, in addition to an engineer, might want to have a chat with a real estate attny.

I have a 40+ foot tall, 30+ year old Fuerte Avocado 6' from a shallow block wall that is not even close to meeting current California Code. No problems. I had a fig and a pine tree about the same distance from the wall that have both had to be removed before they destroyed the wall. The Fig was damaging a walkway on the other side of the retaining wall. i don't think you will find many trees that will damage concrete less than a similar sized Avocado. Don't forget that Avocados need their leaf litter to stay on the ground around the tree for best long term tree health.

Yep, I am in North Carolina, zone 7/8. Crape myrtles are EVERYWHERE here, so I have no concerns about them not growing. I guess one of the questions I need to answer is would I rather keep the crapes and have privacy in 1-2 years, but for only 8 months of the year? Or do I want to move things around and plant a wall of evergreens and not have much privacy for 5 years. If I keep the crapes I may spread them out a bit more. Right now there is 10 ft. between each, but I would like to increase that to at least 12-13ft. I don't really like the look of a crape myrtle hedge where every tree is growing together. Another thought I had was keeping the "miami" crapes trimmed so that they grow a little bit underneath the "natchez" ones, as they are naturally smaller growing anyway. The dogwood I have planted in the photos is in a spot that has about 5 ft. of land between the fence and the retaining wall. Is this too tight? If not, I may move the dogwood and put a crape myrtle there, which may even give me 14ft. between each crape myrtle. Nope I cannot raise the height of my fence at all. My lot is sloped downward a little, so if I play fetch with my dog then my neighbors can't see me which is nice. But if we are on our porch we are very exposed.