Ardnamurchan's Nazca Lines

We're very accustomed to looking down from the tops of hills and seeing areas of flat land beneath us divided into rectangular areas by ditches.  These can sometimes be in places which are miles from any existing village, as with this heavily-drained area which is by the Kilmory turn off the B8007, but we've always assumed they were areas of improved agricultural land.

The winter's dry weather has, however, begun to reveal other ditch systems which don't lend themselves to quite such a simple explanation.  The ditches in this picture of the western flank of Beinn an Leathaid run across land which is rather steep for cultivation....

....while these unusual ditch patterns drain an area on the eastern slope beneath Cathair Mhic Dhiarmaid.  The curved ditch is particularly puzzling.

Like so many things, once noticed we began to find more and more.  These drain an almost precipitous slope of the western side of Beinn an Leathaid and, like those in the second picture, seem to be far from any area of habitation or other workings.  Why is there the sudden kink in the left-hand ditch?

One possibility is that these could be drains cut in preparation for the planting of forestry, but we have checked with the Estate and there is no recollection of these areas being prepared, recently or in the past, for tree-planting.  In any case, they are on very exposed slopes, not ideal even for coniferous woodland.

We then began noticing isolated ditches running across very barren land.  There are two in this picture, which shows the part of the higher slopes in the valley of the Allt Fascadale.  By the time we found these we were.... puzzled.... yet, as we walked up that valley, we found more and more.

Then we spotted these, much higher in the same valley but on the eastern side, cutting across rocky, barren land which no-one would want to use even for tree planting.

The ditches seem to have one thing in common: they all run downhill to a burn or river.  For want of any other explanation, are these some sort of water catchment system, designed to draw water down into burns back in a past age when rain wasn't quite as plentiful as it is today?  Either that, or were the ancient people of West Ardnamurchan emulating the strange lines drawn in the Nazca desert by a lost people in Peru some 1,500 years ago?  If so, can someone please go up in an aeroplane and see what pictures they were drawing.