Abstract
Topographic change of an artificial shallow is investigated experimentally in terms of bottom flow velocity on the surface of the shallow and pore-water pressure on the surface layer of the shallow. Experimental results show that the erosion occurs from the upper part of the slope to the offshore part of the crown, which corresponds to a breaking point judged from the spatial distributions of the wave height and the mean water level. It is also found that the area of the topographic change increases with an incident wave height and an incident wave period. For the shallow composed of fine sediments, a relative vertical effective stress ratio (RVESR) reduces during onshore bottom flow velocity while the RVESR rises during offshore bottom flow velocity, and suggest that offshore sediment transport can be accelerated because it is inferred that restricting force between sediment particles decreases with the increase in the RVESR. Furthermore, it is demonstrated that sediment transport of the shallow can be evaluated reasonably well using a Shields parameter modified to take into account pore-water pressure on the surface layer of the shallow, and consequently it is essential to consider the pore-water pressure when assessing sediment transport and resulting topographic change of the shallow.
