A series of tests were carried out to determine characteristics of the flows over pinched sluices. Effects of volumetric flow rate, feed % solids and slope angle on flow height were measured. An empirical model was developed to define the relationship between operating variables and flow height. Within the experimental range, Reynolds numbers varied between 1200 and 5000, implying that the flow could be classified as upper transitional to turbulent depending on operating conditions. Data also show that turbulence can be suppressed by increasing feed % solids. On the basis of Froude numbers the whole range is classified as supercritical since they varied between 2.6 and 6.7. The abilities of laminar flow, Manning and smooth turbulent flow equations to predict mean flow velocities were tested. None of the equations provided a satisfactory fit to experimental data. The Manning equation was successfully modified into a model to define the relationship between operating variables and mean flow velocities. (C) 2002 Elsevier Science Ltd. All rights reserved.