The present lecture notes cover a first course in th most common types of stratified flows encountered in Environ mental Hydraulics. Most of the flows are buoyancy flows, i.e. currents in which gravity acts on small density differences. Part I presents the basic concepts of stagnant, densit- stratified water, and of flowing non-miscible stratified fluids. The similarity to the (presumed) well-known open channel flow, subject to a reduced gravity, is illustrated. Part II treats the miscible density stratified flows. In outlining the governing equations, the strong coupling between the...