Tool to make river system wider

[Amy35145242khtw]

What's the best tool or tools to help me make a river system wider?  I have a river system with small creeks coming off of it.  I'd like to increase the size of the river (making pixels increase).  The river is 1 color and has a transparent background.  I'm trying to place the river on a T-Shirt but it's too skinny and long to be easy on the eyes.  I've tried the liquify tool but that just doesn't do what I'm trying to do.

[Chuck Uebele · Accepted solution]

I would try making a selection of the river, using color range, then use modify>expand to make it bigger, then just refill it with the same color.