In the old days of the Republic the governorships of the provinces were traditionally awarded to members of the Senatorial Order. Augustus' reforms changed this policy.
Augustus created  the Imperial provinces. Most, but not all, of the Imperial provinces were relatively recent conquests and located at the borders. Thereby the overwhelming majority of legions, which were stationed at the frontiers, were under direct Imperial control. Very important was the Imperial province of Aegyptus (modern Egypt), the major breadbasket of the empire, whose grain supply was vital to feed the masses in Rome. It was considered the personal fiefdom of the emperor, and Senators were forbidden to even visit this province. The governor of Aegyptus and the commanders of any legion stationed there were not from the Senatorial Order, but were chosen by the emperor from among the members of the lower Equestrian Order.
The old traditional policy continued largely unchanged in the Senatorial provinces. Due to their location, away from the borders, and to the fact that they were under longer Roman sovereignty and control, these provinces were largely peaceful and stable. Only a single legion was based in a Senatorial province: Legio III Augusta, stationed in the Senatorial province of Africa (modern northern Algeria).The status of a province was subject to change; it could change from Senatorial towards Imperial, or vice-versa. This happened several times during Augustus' reign. Another trend was to create new provinces, mostly by dividing older ones, or by expanding