Abstract: This invention relates to river control structures, of the kind known as upstream tilting gates. A structure in accordance with the invention includes a chamber, (1, 2, 3 and 4) and a tilting platform (5). The upstream end of the platform includes a curved transverse wall (10), consisting of a plurality of leaves (12 and 13). When the platform is raised, the leaves provide a continuous wall between the platform and the top of the chamber, while when the platform is lowered, the leaves slide behind each other and are accommodated in the chamber. The structure also includes a channel (7, 8 and 9), extending along the length of the platform. The channel is provided with baffles to limit the flow of water down the channel, to enable fish to surmount the structure.