This drone footage illustrates the value of that filtering function, where a waterway flows alongside a lane used by dairy cows as they walk to and from the dairy shed. A narrow strip of native sedges line the small drain and the plantings are so dense that you can barely see the water. The filter strip would ideally be wider, but it is still doing a far better job than an unplanted riparian strip. That's because the plantings not only filter overland runoff, but their shade is preventing nuisance growths of aquatic weeds, while the leaf fall is helping with nitrate removal via denitrification.

Thanks again to Derek Gerber for his cool hand on the drone controls.