Busy family driveways in Helensvale produce a steady stream of low-speed impacts: a reversing vehicle, a bike, a bin on a windy morning. The bottom section takes most of it, and it is also the section that carries the bottom brackets and the floor seal, so damage there is never purely cosmetic.
Whether a single section can be replaced comes down to matching. The replacement has to share the existing profile and rib pattern to fit the hardware, and it has to be close enough in colour to look acceptable next to sections that have been in Queensland sun for a decade or more. That judgement has to be made in front of the door, which is why nobody should promise it over the phone.