[mandrill7]

This worked great for putting in rivers that were not made by Microdem. I tried it out a few times on an inland map, with no coastline. Rivers came on the map.

But, I seem to have gotten them as deep canyons, not as rivers that flow more or less level with the surrounding land.

Here is what I mean:

Looks nice for a canyon landscape, but for the map I'm working on it is not really the way it should be.

So my question is, how does one make rivers run more or less level with the surrounding land? How to avoid the deep canyon effect?

You need to modify the map_h. Another consideration is that you can only build bridges at sea level. This means you have to have your rivers at sea level, if want to put in a bridge. The sea level colour in the map_h is RGB "0", or pure black.

So this is what I did for my Russia map. Lay the map_h over a reduced version of your map_c with all the rivers drawn in. Make the map_h layer sufficiently transparent so you can read the course of the rivers "through" the map_h. Then paint the map_h RGB 0 along the river courses.

I was fortunate that my map had no mountains or even hills. Therefore, I could paint huge chunks of the map RGB 0 without creating chaos.

Blur the edges of the RGB 0 areas to avoid getting sudden cliffs and canyons. You want to make the RGB 0 painted areas sufficiently wide that you do not get steep canyons around your river banks.