I need not fiddle with actors.static at all. Here's what's required.
Where there are no shoreline villages/buildings: Map _h.tga will require a few tiny elevation reductions at river banks where the river has slightly moved up onto higher terrain.
Where there are villages/buildings: Map_c.tga will require to restore the former river bank position, smoothly integrating it into the new river course.
In a few places the river has intruded into the forest, and so map_T.tga should have a pixel or two here and there reassigned so that 'laker cake' trees not appear on water.
For me, personally, this work is worth the effort. As a student of geomorphology, 'blocky' river courses somewhat quantized in places to a pixelated grid is jarring to behold, and detracts too greatly to be endured. On this map rivers are a very prominent feature, and so should be rendered reasonably realistically in the smoothly curving manner of the real thing.
I'm doing this first of all for me. I thought that if anyone else might like it I'd make it available...