I've been an dozer operator, self employed, not "owner operator", but directing clients to rent needed machinery, for 30 years. I've worked as a surveyor for 25 years and for about 23 years I've generated custom large scale topos for construction, grading and drainage plans for a civil engineer.
I specialize in drainage on steep mountain roads as a operator. Finish drainage, by eye, from the seat of a dozer has been a focus that people really appreciate. I've recovered many roads here in these coastal mountains that were destroyed by the lack of drainage or improper drainage. My drainage works well enough so that I put myself out of work, because roads only need light maintenance of drainage devices after I'm done.
We have highly varied geology here that really provides huge challenges. Or, there is a 50 mile wide strip in the back country here that has no paved roads because there's no guarantee that sections will remain after next years rains.
I've just made a youtube channel and web page to attempt and sellvideo of grading and drainage work I've done from 2006. I need to support the political activism I do in pursuit of peace and environmental protection through defense and restoration of the constitution by American citizens using Article V properly, by preparatory Amendment. A .pdf about the strategy.
I also have developed ways of saving the natural seed bearing surface soils off to the sides, then bringing them back after the earthwork. A few smaller jobs about (300cu yds) were actually completed that were turned into county agencies by vengeful nieghbors because there was no permit. But when they were inspected by county grading officials, because natural grasses were sprouting everywhere (much water applied) and the owner was talking about "clearing and drainage", they could not determine what had been done, had no problem with anything, so left with no violation.
I suspect this method will work well for permies because the cost of topo and design will be a turn off.
Use of an abney to set grades with marker lathes and hiked up flagging http://www.ascscientific.com/8047-55abney.jpg is all that is needed along with a good operator having prodecdure and an eye for locating daylight points on cut slopes and toe points for fills.
Back to swales:
In about 1992 I started installing what I called the "Serpentine Swale" with a D6D cat that was available. It worked on slopes up to 20%, but with a 10' blade a lot of dirt was moved to get a flowline. They were installed to give water time to exert its hydrostatic pressure on sub soils and charge them with water just as the keyline. The original need was to get rid of outlets of water bars installed on ranch roads without erosion.
I was fortunate to have a house near enough on the first one to advise them to use it for a garden because I expected ambient moisture levels to raise dramatically. It worked in the fractured shale quite well and soon the area which hadn't really worked for a spring household crop, because it was dry and far from water. After the first year and the spring successes, they ran a small waterline to take a summer garden crop all the way through.
There was enough absorbtion, where the outlet, even in heavy years saw minimal erosion.
In 1998 I started making them in Mendocino county on a smaller scale with a high trak D4 cat, to stay away from steeper slopes where heavy cutting and filling was the only practical method. Also, as some of the posted videos here indicate, slope stability and integrity can be seriously effected over time adding mass water to a slope.
The "Serpintine Swale" has a constant fall of no less than 3% and max of 10% for a short distance, usually in a switchback.
I've thought of the "Keyline Swale", but in the steep ground I work in the chances of slope destabilization have often been too great to take the water of a natural flowline and move it out to a ridge. Also, the chances of over-run and question of "where the water goes" gets sticky. I would consider that in the right geology, it could be run back to the natural flowline.
The average slopes over distances between ridges and valleys/flowlines are not very great in those examples, so destabilization is not a great threat.
For steeper ground, which turns out to be the most affordable because of the costs and limits inherent to it, roads act as keylines, but running a flowline down a road will almost always destroy it. However, a road traversing a slope acts as a slope interceptor meaning flow concentrates and must be taken off. If there are flatter areas near the outlets of water bars, taking negatively drained flow, concentrated, to positive, discharging off the road downslope, then you have the situation where I developed the "Serpentine Swale" to deal with the water and erosion.
Hope this brings some loose ends together in determining how to increase ambient moisture for permaculture.