AN EXPERIMENTAL STUDY ON THE EFFECT OF SAND COMPACTION ON THE TOPOGRAPHY CHANGE OF SAND NOURISHMENT

Abstract

 Beach nourishments are implemented in many areas for the countermeasure against coastal erosion. Regarding the investigation of beach nourishment, laboratory experiments focusing on the particle size, mixing ratio, and cross-shore location of beach nourishments have been conducted. However, it cannot say that it is sufficient to examine how much the initial compaction degree of nourishment area contributes to the topography changes of the nourished area. Therefore, we conducted laboratory experiments to investigate the effect of the initial compaction of the beach nourishment on the erosion (topographical change) of the nourished area due to waves. The results revealed that the lower degree of compaction of the beach nourishment, the more significant erosion (topographical change) occurred immediately after wave generation, and the difference in erosion rate between the compacted and loose nourished sand was about twice. Moreover, when the wave overtopped the beach nourishment area, the influence of the compaction degree of the nourished area on the erosion volume is smaller than when it does not overtop the nourished area. On the other hand, when the waves did not overtop the beach nourishment area, it was found that even if the topography shape after the experiment was the same, the degree of compaction of the remaining topography was different.