A method is provided for installing a barrage across a body of water for generating electricity or current flow, the barrage being formed from a series of modules, each of which comprise a base structure carrying a number of substantially vertical pipe structures in a spaced, side-by-side arrangement, and a deck structure extending across the top of the pipe structures and supported by at least two pipe structures, the method comprising: preparing a series of foundation terraces across the bed of the body of water substantially perpendicular to the direction of flow, each foundation terrace providing a substantially flat base on which the base structure of one or more modules on the terraces side by side such that the base section of each module rests on a terrace and the deck structure of each module is located at substantially the same height as that of its neighboring modules.