An approach to the problem of the evaluation of horizontal flux of sediments in high energy environments by the use of a new passive sediment trap

Summary form only, substantially as follows:- The problem under investigation is the evaluation of the horizontal particles fluxes in high energy environments like all the sites where strong current flows do not allow the particles to sediment but cause mainly a consistent horizontal flux of material. In this type of environment traditional sediment traps do not work properly or at all because of the eddies generated by the interaction of the edges of the trap mouth with the stream of the currents. The authors propose the use of a new design trap, in which the horizontal water flow is driven through a variable geometry but constant section channel and forced to assume a laminar structure before to get into a "trapping area"; the trap effect is obtained by entering a death space (referring to Gardner's definition) in which the sudden decrease of velocity causes a particle precipitation. Different prototypes have been realised, based on the same principle but with different design of the adduction channel and with different geometry of the interface between the channel and the trapping area. The prototypes have been built not at the real dimensions, but with a scale factor of five, to be able to test the equipment's in a laboratory facility. The authors tested their apparatus first in free moving water, to evaluate its hydrodynamic behaviour in different external velocity fields. A second test phase has been conducted, and is still in progress, in a forced flow of water, artificially enriched of a known amount of known particles.