The present invention relates to an apparatus and method, using the apparatus, for blocking the passage of solid materials into or through a channel while permitting the passage of fluid; automatically releasing the blocked solid materials under predetermined conditions when priority is given to maximizing the passage of fluid; automatically re-closing after the accumulated solid materials have passed downstream, and resuming the blocking of solid materials; and, repeating the process upon recurrence of the predetermined conditions. Although the invention relates to street storm-water drainage channels, particularly inlets to catch basins, it can be applied to any fluid-flow channel where blocking the passage of solid materials is important but where there are conditions under which priority should be shifted from blocking the solid materials to releasing them downstream.