Numerical Simulation of Volume Change of the Backshore Induced by Cross-Shore Aeolian Sediment Transport

Abstract

Predicting the morphological changes of the backshore is vital for appropriate beach management because the backshore plays a significant role in the ecosystem and disaster prevention. In this study, a one-dimensional model was developed and applied to the Hasaki Coast in Japan to predict changes in backshore volume. The volume change was estimated from the difference between the aeolian sediment transport rates at the seaward and landward boundaries of the investigation area, considering the wind velocity and direction, sediment size, precipitation, and vegetation in the process. The model was calibrated and validated using the first and second halves of beach profile data obtained weekly at the Hasaki Coast over a 28-year period from 1987 to 2014. The validation suggests that the model can reasonably reproduce the cumulative volume change, which is the amount of volume change from the initial value, but it underestimates the time-varying fluctuations of the weekly averaged volume-change rate. This can be attributed to the presence of small-scale features, such as dense vegetation and wrack, which are not taken into account in the model. Although the model performance for the cumulative volume change was good, it overpredicted the values in the second half of the validation process. This can be attributed to the fact that the model is not able to predict reductions in the aeolian sediment transport rate caused by an increase in beach steepness.

Keywords

• beach profile
• dune
• vegetation
• Kawamura’s formula