This International Standard specifies the methods of measurement of flow in rivers and artificial channels, using any combination of standard weirs and/or flumes in a compound structure. For guidance on the selection of weirs and/or flumes, refer to ISO 8368. All structures can be operated in the modular flow range, but only a limited number of structures can be used in the drowned (non-modular) flow range (see clause 4). Compound weirs improve the quality of discharge measurements at low stages.

The characteristics of velocity distribution are described annex A.

Structures standardized for operation in the drowned (non-modular) flow range and the method of computation of flow are described in annex B.

Methods and examples of flow measurement calculations are given in annex C.

Compound flow-measuring structures without divide piers need in situ or model calibrations and are not covered by this International Standard.