All five managed to get out of the vehicle and Emily was being carried to shore when she was swept away.
Petrie swam after her, but was also swept downstream.
His body was found the next day but little Emily was never recovered.
Her parents both survived.
Saunders has now been charged with dangerous driving causing the deaths of Emily and Petrie.
Police confirmed he appeared in the Christchurch District Court on Friday.
A spokeswoman told the Herald that the charges were laid "some time ago" and that Saunders had appeared in court a number of times already on the charge.
His next court appearance is set for June 22, when a trial date is expected to be set.