Abstract: The invention provides a road spillway comprising a porous removable deck over a ditch across a road. The road has a surface for driving on. Solid supports are provided on opposite sides of the ditch and below the surface of the road. Span members span the ditch generally below the surface of the road, removably resting on the solid supports. Deck members are positioned above, and attached to, the span members. A rigid grader bar may be attached to the top of the deck members, spanning the porous deck. The span members and deck members form a porous deck resting on the supports and spanning the ditch. The deck has a top for driving on which is generally at the level of the surface of the road. A settling pond may be provided in fluid communication with the ditch.