I can't speak to what happens down under, but in the USA
most changes are to the various Aids to Navigation
as they get moved, changed, removed, and updated.
Dredging and shoaling are also updated, but usually only in improved channels.
Permanent (and temporary) changes to charted information are all summarized in the Local Notice to Mariners (LNTM) published by the USCG weekly in regional editions. They used to be an important part of running a vessel, but most people seem to not even know they exist any more. An unfortunate side effect of "video game" sailing.
When worked as a sailing instructor in the San Francisco
Bay area we regularly corresponded with the USCG officer responsible for the LNTM and get required changes to charts into the update flow. Generally, once an update was confirmed, it appeared in the online published charts within a week or two.