Gutter snipe

The length of the gutter channel is perforated with small holes at roughly 5cm intervals. Behind each hole is an electrically-operated pneumatic valve, holding back air at a pressure of about 10 bar.
At the end of the channels, ultrasound and laser rangerfinders detect falling leaves, and a microcontroller activates the nearest valve, ejecting a puff of air and blasting out the offending foliage before it has chance to settle.
Complex military-grade clutter rejection algorithms and air temperature sensors will be used to avoid false triggering by rain and snow storms.

To demonstrate that the unit is functioning correctly, every fifth valve will be fitted with a small tuned whistle, and the unit's self-test software will play "Les feuilles mortes" at random times of the day. Or night.