Beach profile model taking into account the time-space variations of sediment density has been developed and compared with the movable bed experiments in the laboratory wave flume. Concretely, the conventional sediment transport load using the velocity moments with use the fluid acceleration is revised considering the time-space variations of underwater specific gravity of sand particles in the activation depth based on the X-ray CT scanning. Conducting the numerical experiments, the fluid acceleration (horizontal pressure gradients) is found to have an inverse proportion to the underwater specific gravity of sand particles in the activation depth. Preliminary attempts to parameterize the time-space variations of underwater specific gravity of sands appear promising.
