This novel was written in the 1980s (I think).
It took place on a lost or abandoned colony. There was an island where a man was hiding with debt notes from friends who didn't want to be paid off with fiat currency (it came with slow agonizing death from killer plants). One character's name was I think "Shulamit(h) Well(e)s". There was one scene in an underground tunnel with a river flowing through it. Two brothers were on the side of the revolution. There were shady characters’ attempts to arrest opposition legislatures.