This document gives guidelines for selecting a particular type of flow measuring structure for measuring liquid flow in an open channel. It describes how the individual structures function in simple non-technical terms, and sets out the factors and parameters to take into account in order to make an informed decision on which type of structure to use.

Values of the relevant parameters describing the limitations and uncertainty involved in the use of these structures are given in this document. More definitive details of a particular type of structure are given in the individual standards listed in Table 1, which cover each type of structure.