Is there any reason a stormwater drain can't be attached to fence, arbor or other structure?

Hello

I've just bought a house where the slab is lower than the street, (but roof is higher than the kerb). So there's some negative grade at the front. The yard very gently tapers down from front to back around 1 or 2% according to the inspector, but to me, the back yard just looks flat.

There's no existing drainage at all that my building inspector can see. He suspects the 2 existing roof drainpipes just terminate in the ground somewhere. The house was probably built in the 1980s and I've been told it's not worth paying the council fees for searches for private drainage as it's probably historical.

I don't want a charged system / pumps but will probably have to settle for a rubble pit in the backyard (Moreton Bay area).

I very much want the front drainpipe/s plumbed to the kerb. I'm worried though that due to the negative slope there won't be enough fall. I have a carport front left to the house, and to me, it seems logical that the drainpipe could extend onto the carport roof (if this is OK) and then maybe diagonally come down the side until it can be buried under the nature strip. If this isn't compliant, then maybe attach the drainpipe to the fence, or an arbor or some other structure?

I've been learning as I go so hope all this makes sense. I've spent a lot of time searching forums but can't find much at all on extending out the drainpipe and / or attaching to a structure to gain extra height and length so the drainpipe can extend out to the kerb.

I would appreciate any advice. There's no measurements at this stage as I haven't taken possession yet.

Thanks.