diverge (as in branch out, like tree limbs) v.i. divaricate

After a 3,000-mile journey across five national borders, [the Mekong], the mother of rivers divaricates into a complex delta network and drains into the South China Sea. (Ben Mauk, “A People in Limbo,” The New York Times Magazine; 03/28/2018.)

This word, when used in the above sense, can also be a synonym for branch (out), split (off), and spread (apart).