Over thirty years ago I built an interesting house for a client. Designed to be very energy efficient. Backed into a hillside and super insulated. Lots of solar gain through glass in the roof. The architect left a LOT of details up to me, like how to seal the glass.
One feature was a long deck above the walkway to the front door. I had a series of troughs fabricated out of aluminum and installed them between the joists for the deck and sloped to the outside. Along the side there was a gutter that caught the water and delivered it to the ground. Assuming that critters and debris would find their way under the the decking we made the deck floor out of a series of "pallets" or squares that could be lifted out to clean under them. The whole thing worked well. There was a ceiling below to improve the appearance. A side benefit was it kept the water off the joists and framing and it lasted better than most.