Making Hand-drawn Style Rivers in GIMP

[Gamerprinter]

I recently did a map with black line rivers, of course I just draw them with a mouse, but since I use a vector application instead of an image editor (like GIMP, PS), I don't need to use an Eraser to taper the source of the river - most vector apps allow for shaped lines, that is I draw a line of a specific point size and the taper appears automatically, as the line diminishes in width over the length. Your technique certainly accomplishes the same thing, but with far more steps to accomplish the same thing in vector. Good tutorial, though.