This International Standard provides a summary of recommended methods for the determination of liquid flow in tidal channels, special consideration being given to those techniques that are either unique to or particularly appropriate for application under tidal conditions, including treatment of uncertainties. Reference is also made, where appropriate, to methods for the determination of flow in non-tidal channels, but attention is drawn to their limitations with respect to practicality and/or uncertainty. This International Standard does not describe alternative methods, such as the use of weirs, flumes, dilution gauging, salt velocity and floats, although they might be suitable under certain conditions, especially where the effect of tides only impedes and does not stop or reverse the passage of stream flow. These methods are described in detail in other International Standards. This International Standard specifies two types of technique: techniques for single measurements of tidal flow; techniques for continuous measurement of tidal flow. AnnexA specifies the cubature method of measurement. AnnexB specifies methods for the determination of flow under tidal conditions, and AnnexC gives an example of the computation for a single vertical. Similar computations are possible for other verticals. AnnexD describes the determination of tidal flow using an acoustic Doppler velocity meter.