Shoreline Devastation of Hota Coast by Man-made Causes

AbstractThe impact of the removal of a river mouth bar as a measure against river mouth closure to the surrounding coasts was investigated, taking the Hota coast as an example. Also, on this coast, landfilling was extensively carried out to build a coastal road along the coastline, resulting in the narrowing of the natural sandy beach. These anthropogenic factors affected the overall shoreline on a pocket beach, devastating the natural coastal environment. We investigated the effects of these impacts using aerial photographs and field observations

Numerical Simulation on Sand Accumulation behind Artificial Reefs and Enhancement of Windblown Sand to Hinterland

Salients were formed in the lee of two artificial reefs (submerged breakwaters) constructed on Kimigahama Beach in Chiba Prefecture, Japan, owing to the wave-sheltering effect of the reefs, and then, a significant amount of fine sand was transported inland from the salients by wind action. In this study, not only shoreline changes after the installation of the two artificial reefs but also beach changes caused by windblown sand were predicted using a model, in which the BG model (a model for predicting three-dimensional beach changes due to waves based on Bagnold’s concept) is combined with a cellular automaton method. Reproduction calculation was carried out on the basis of field data. Beach changes after the artificial reefs were removed were also predicted and the effect of beach nourishment was investigated. It was concluded that landward sand transport by wind is accelerated when wave-sheltering structures such as an artificial reef are constructed on a coast composed of fine sand, and such an effect can be successfully predicted by using the present model