This dataset contains flume experiment data from a series of runs that were performed at the Eurotank laboratory of Utrecht university. It includes velocity data as well as photographs that were taken from the deposits emplaced by the density flows inside the flume. The flume was 3.7 m long, 0.22 m wide, and 0.5 m high with glass side walls. For the experiments, the slope was adjusted to 6, 8, and 9.5 degrees. Before the runs, mixtures composed of 1) sand, silt, clay, and water or, 2) sand, clay, and water, were prepared and stirred for approximately 30 minutes to 2 hours in a 0.45 m3 mixing tank and the flume was filled with tap water. The sediment volume concentration was varied between 9%, 15%, and 21% and contained  2/3 sand and 1/3 clay for the runs without silt and 1/3 sand, 1/3 silt, and 1/3 clay, for the runs including silt. The mixtures were then pumped with a discharge rate of 10 or 15 m3/h into the flume. Velocity data was obtained using two Ultrasonic Doppler Velocity Profiler probes (UVP Duo Mx, 1 MHz) which were placed at 0.7 m and 2.7 m distance from the inlet, at a height of 0.11 m above the bed, and with an abgle of 60 degree to the bed, facing up stream. This dataset was used in Hermidas et al., 2018 to classify clay-rich subaqueous density flow structures.