Andy,
CAR 157 Low Flying
(1) An aircraft must not fly over:
(a) any city, town or populous area, at a height lower than 1000 feet; or
(b) any other area at a height lower than 500 feet.
(3) A height specified in subregulation (1) is the height above the highest point of the terrain, and any object on it, within a radius of:
(a) in the case of an aircraft other than a helicopter – 600 metres; or
(b) in the case of a helicopter – 300 metres;
from a point on the terrain vertically below the aircraft.
There are exemptions enumerated under subregulation (4) (a) to (h).