Flat roof drains made of Ecoguss or polymer. In addition to a practical leaf trap to prevent blockages, flat roof drains are also available as an option in heated versions to secure the functional capability.
DIY - How to install a drain pipe from the gutter of your house to drain to your backyard. Pictures of the concrete, burying the pipe, digging the trench, sand backfill and PVC pipe. Material list and prices.