Transport of tsunami-driven debris over a slope

• Transport of spherical debris induced by breaking solitary waves over a slope covered with sediments is study experimentally. • Shown, that fine sediments on a slope support debris deposition offshore and turn into marine litter, while coarse sediments support debris deposition onshore. • Heavy debris are more likely to move offshore while light floating debris are more likely to move onshore. • Debris initially located in wave pre-breaking zone are likely to be transported offshore, while debris initially located in wave post-breaking zone are deposited onshore over a maximal distance. • The succeeding waves have cumulative effect on debris transport. The second wave almost anchors the debris to their final location and the third wave barely moves it. The range of debris displacements for single and multiple debris grouped in a row overlap, which means that debris grouped in a row do not interact between each other. We study tsunami-induced transport of heavy and floating debris over a slope. The work is performed experimentally in a small wave flume, which is 3 m long and 0.1 m wide with the water depth of 0.05 m. Tsunami is modeled by breaking solitary waves with amplitude ( a ), normalized by the water depth ( h w ) equal to a / h w = 0.5. Three succeeding waves propagate towards a sedimentary beach breaking on the slope, and impact debris which are initially placed at different locations along the slope with respect to the wave breaking point. We use spherical debris with two different densities. The heavy ones are lying on the slope, while the light ones are floating at the surface. The sea bed slope is covered with 0.02 m layer of sand. We use sediments of two different sizes to study the interaction of debris with sedimentary environment. The main measured parameter is displacement of the debris along the slope, which is analyzed with respect to the characteristics (densities) of the debris, their initial positions, number of consecutive waves and the size of the sediments