LABORATORY EXPERIMENTS ABOUT BED PATTERNS IN THE SHOALING REGION UNDER REGULAR WAVES AND REFLECTING CONDITIONS

This research is an experimental study of ripple dynamic for regular waves propagating on horizontal and sloping beds in mid- and high-reflecting conditions. Small-scale laboratory experiments were carried out on shoaling region (waves did not break) and sediment transport in bedload regime. Spectra of the bed profile were obtained. Our experiments showed the key role that plays the reflection in ripple development. The spatial modulation of the free surface elevation due to reflection created sandbars. Ripples grew up in the region where sandbars were appearing. These patterns were gradually reproduced from breakwater to offshore. The incidence of sandbar created a bi-modal structure of ripple geometry. Our results showed larger ripples in the crest of sandbars and smaller ripples in the troughs. Furthermore, the ripple evolution of these two locations followed different growth mechanisms. Finally, at equilibrium stages, ripple height converges reaching the same height along the sandbar while ripple length and steepness remains almost constant.