Gravel & stones
Ferns, black mondo grass, and the hakonecloa (Japanese forest grass) make great plantings at the base of rainchains - they'll thrive with the added moisture! And the river stones will help prevent muddy splashes - as well as (w/ some grade management) disburse any rainwater that might pool there... All this while enhancing the near-by patio! What a well-planned design!
mixed size cobble stream, very effective against these grasses -Black mondo grass and Hakonechloa macra 'All Gold'