ABSTRACT
The evolution of the bed surface and bedload transport rates under a sudden increase of the water discharge (pulse) has been relatively unexplored in an experimental setup. Further, no systematic investigation has been performed to analyze the role played by the frequencies at which these pulses occur in the bed adjustments. This contribution presents a novel experimental investigation which aims to shed some light on: (i) how river bed evolves to variable flow conditions under constant sediment feed and (ii) what is the influence of the precedent morphological history in these adjustments. Water pulses of fixed 1.5 h of duration were alternated after periods of low flow of variable duration-from 1 h to 10 h. Runs were performed at a constant sediment feed rate of 7.50 kg/h during both low and high flow periods. Eight consecutive runs were performed in such a way the final configuration of the previous run was the initial condition for the subsequent experiment. Preliminary results show bed structuring (when it is partially destroyed by a sudden increase of the water flow after a long period of time of no feed and when it is reconstructed after a series of pulses) can play an important role in sediment transport regime in gravel bed rivers.
