AbstractThis paper examines whether horizontal free surface flow patterns can reveal bulk river flow characteristics, such as the Froude number. To do this, the Froude number was measured between 0.2 and 1.2 by visually observing the flow patterns around a wooden stick, the so‐called ‘Froude stick’ described in the literature. The stick has been hypothesized to estimate the Froude number at the transition between subcritical and supercritical flow based on free‐surface flow patterns. The study objective was twofold: to obtain (i) a measure of the Froude number independent of estimates of water velocity and stream depth; and (ii) a tool that would allow the field biologist to assess hydrodynamic properties of streams. The results show that the stick measures only water velocity. As water velocity increases from about 0.2 m s−1, to 0.45 m s−1, an obtuse V‐shaped flow pattern around the stick obtains a right‐angle that is easy to detect by the naked eye, and wavelets upstream of the stick are more than 1 cm wide. With increasing water velocities the V‐shaped flow pattern becomes pointed, and at velocities a little larger than 1.0 m s−1 the upstream wavelets disappear. Copyright © 2004 John Wiley & Sons, Ltd.