Open ftomassetti opened 10 years ago
http://ranmantaru.com/blog/2011/10/08/water-erosion-on-heightmap-terrain/
Or this:
http://www.blitzbasic.com/codearcs/codearcs.php?code=2443
http://ranmantaru.com/blog/2011/10/08/water-erosion-on-heightmap-terrain/