if you create heightmaps( raster images ) like waldronate and i do besides wilbur there is Qgis and the r.teraflow GRASS plugin
see my last update to the April challenge
https://www.cartographersguild.com/s...ad.php?t=40181

look at the difference in post 3 and 4
-- it is small but there
there is also a tool Just for rivers , though i have not used that yet

also qgis can remap to one projection and then back to the original
-- something g.projector can NOT do