Kuri...If you flush them down the drain there is a very good chance that there is leaf mater left in your drainage pipe and that will point to your house. Once it enters the main then good luck finding the source. I promise you, if you flush your trim down the drain there will be some left in your drainage pipe that could be discovered at some point and time.

You may want to rethink that approach and use generic trash bags and rubber gloves so there are no finger prints (if you are in the system) and dispose of your trimmings in an industrial waist can. Just make sure there is no cameras filming you.