Multicamera, multimethod measurements for hydromorphologic laboratory experiments

The realization of hydro-morphologic laboratory experiments on propagation of aggrading or degrading sediment fronts required a simultaneous measurement of the sediment feeding rate, profile of the free surface and of the flume bed elevation. In this study, five action cameras and different image-processing techniques were employed to measure all the needed quantities automatically and with adequate temporal resolution. The sediment feeding rate was determined measuring by Particle Image Velocimetry a surrogate, correlated quantity: the surface velocity of the sediment flow along a vibrating channel used as an upstream feeder. The profile of the free surface was measured shooting an array of piezometers connected to the flume; each piezometer pipe contained a buoyant black sphere that could be recognized using tools for particle identification, thus determining the elevation of the free surface above the piezometric probe. Finally, the bed profile along the of flume was measured at any instant by edge detection, locating the transition from a water layer to a sediment layer in images taken from the side of the flume. The manuscript describes the instrumentation and the methods, finally presenting the results obtained from a prototypal experiment. Potentialities and limitations of the proposed methods are discussed, together with some prospects on future use in systematic experimental campaigns.