I primarily wanted to make some irrigation ditches for my Afghanistan terrain set. They could then be used in almost any other setting I commonly game as an added bonus.
I didn't want to make raised terrain bases so I could then sink ditches into them because I think it looks wrong so I had to come up with another way of showing the ditches on the table top.
I noticed that the path of ditches can often be traced by the vegetation growing in them or next to them. Typically this vegetation is more lush than the surrounding areas because it has access to the water in the ditch.
My plan was to indicate the presence of ditches by lines of vegetation rather than the ditches themselves. Illusionary ditches in fact.

I used pre-cut 2mm MDF bases because I had them handy but any usual basing material would have been as good. These ones are from Wargame-Models-Mods.

I bought a soft bristled broom head for less than £5.00 from eBay.

I cut off clumps of bristles of different lengths from the broom head and fixed them in place with hot glue.

I left gaps between the clumps to try to keep it looking natural and not a planted hedge. ​

I made corner sections as well as straight sections in preference to just having straight sections arranged at 90 degrees to show corners because I liked the look.

I painted the hot glue the same colour as my basing mixture and then added the mixture (PVA, paint and sand) in clumps with railway ballast scattered on for more texture. ​

I continued adding the basing mixture and ballast in sections until everything was based. I added the basing in sections with drying time in between to minimise the risk of the thin, narrow bases warping.
It didn't work, they warped, but a coat of PVA glue on the underside once everything was dry straightened them out again.

I painted the bases in my usual two tones of sand and added static grass in lines in the gaps between the bristle bushes.
In hindsight I probably didn't need the static grass, the illusion was good enough without it and it might have over egged the pudding, less is more with things like this. Still, it's done so I'll live with it.

Here are the ditches with some 28mm TAG Taliban for scale. Obviously they're not laid out as they will be for a game where they'll run between fields and alongside roads etc.

So there we are; quick, simple and relatively cheap irrigation ditches.

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