Turbidity currents are the main source of suspended sediment transport in reservoirs and thus one of the main causes of sedimentation. One of the techniques used to avoid reservoir sedimentation is through venting of turbidity currents. In the framework of a research work on venting, velocity measurements of turbidity currents flowing on a flat bed are carried out using Ultrasonic Velocity Profilers (UVP). Five profilers of 4 MHz placed at different positions in an experimental flume provide velocity profiles. Body and head velocities are analyzed and used to calculate the characterizing height and velocity of the currents. The flow regime is described based on Richardson number. Results show decreasing velocity values and thus the deceleration of the currents. Front velocities are also investigated.