@Dorian: That's the fractal noise BigBen put over the dem. I could reduce that (I already did a bit). I didn't use a compute terrain here, so if detail up close is more important than render time, I can use one and have some more lateral displacement, and perhaps smooth that 'erosion' out.
Edit: if you look up close to that valley and wadi in google maps, you see it's a different ballgame; dry riverbed and 'alpine'like edges of the ravine. If you want to go this close that means work on that area in detail (I think even an image map, can't do that very precisely with the painted shader).... a bit of a waste if the director thinks the Suez would be better, though. And the extent of such an image map would depend on exact camera positions...