I'm doing some second-guessing here, but it seems that you must get stormwater from the back yard to the front. Since the former french drain is non-functional, I'm wondering if you can change it to a slot-covered trough drain that collects water at the critical places and then directs it via underground pipe to an outlet somewhere toward the front yard... ?? Since you won't be hiring a hydraulic engineer, I would lean toward keeping it oversized... thinking about those big storms and the fact that drains tend to collect "stuff" and become clogged. 4" pipe is too small. 6" or a pair of them would be better. (If you can figure a way to keep it above ground, even better.) The exact details of how you constructed it would depend much on how the plan shapes up and what else you're constructing. Being as it's your own yard and your doing it on the cheap, you might even consider constructing a removable slotted grate made of treated wood. It wouldn't last like other materials, but you could get a few years out of it. In regards to planting on the hill, I'd be in favor of getting rid of all grass, thinking it's not fun to maintain, creating instead a solid small flowering tree canopy that would be limbed up with a high ceiling. Below it, a single, solid groundcover. Trees that come to mind would be redbud or saucer magnolia, with a preference for the former. 5 trees in a double staggered row (3 at back, 2 at front would do it.) A super cheap groundcover would be virginia creeper as you can find it everywhere and start your own cuttings. It's pest free and grows about 12" tall. You'd be able to incorporate other plants at edges, once some shade is up and running, and in the sunny areas.

It doesn't matter what type of water is used - the distilled water example was just to illustrate how inaccurate they can be = equally inaccurate no mater what kind of water is used. It's not just fertilizer salts that would affect how wet/dry the meter reads, it's ANYTHING dissolved in the soil solution. It's probably good that your gauges are gathering dust - your instincts and fingers are better measurers of soil moisture than the gauges. The cheapo gauges are also horribly inaccurate as a device for measuring pH because they can't be calibrated, not to mention the fact that 99% of the hobby growers who would aspire to measuring pH wouldn't know how to do it so as to ensure an accurate result, even assuming the gauge was accurate. Then, after getting a result, what to do then? A hobby grower trying to maintain a stable pH in containers is not unlike chasing a fart in a wind tunnel. I'm not pushing 'the basics' particularly, but when you do get the basics right, there is very little need to fuss with a plethora of gadgets, gizmos, and the dozens of products that promise miracles. If growers are limited by inattention to the basics, there is nothing a gadget or the promise of a miracle can do to make up for it. How I grow is extremely simple and extremely effective/productive. I treat all my plants alike, except maybe cacti - water when I think the plant might need it - only being careful not to overextend the interval between waterings, but never worrying about over-watering. I use ONE fertilizer and fertilize on a schedule that doesn't vary much, other than according to ACTUAL dormancy of temperate plants - I lay off those for the winter, but not those plants kept indoors. I make my own soils, which is sometimes difficult to get started at, but extremely easy once you're set up. I have no problems with retarded growth, or spoiled foliage, and disease/insect infestations are rare as hen's teeth. The most complicated thing I do insofar as maintaining a plant's level of vitality is root work, so there is nothing I do that others that wish to can't do as well .... and as well. Al

myplant, you do realize that for the most part these are dormant in the north? They will lose all their leaves and only have stems left for most of the winter. The root is like a bunch of carrots, storing nutrients to make new leaves in the spring. Place it in a spot where you can watch it and allow it to go almost completely dry for the winter. Water it only after the dirt is dry for a week or more. Long about late Feb, you should see green sprouts starting on the stems. At this time, prune it hard, place it in good sun, and water it. After this, never allow it to go dry until next fall. The plant needs a rest so that it can come back in better shape next growing season. Might be advice for you too. Take care.

That appears to me to be the leaves are loosing moisture faster then the rotos can supply it. This can be because of insufficient watering or too much watering.