349 / 2024-02-29 18:42:02

Numerical experiments on the effects of coastline alteration on circulation patterns in Hakata Bay

three-dimensional numerical simulation,coastline alteration,Hakata B

Coastline alteration due to reclamation works affect current patterns in inner bay of closed waters. It is important to examine the effects of coastline alteration on current patterns, as these patterns are a significant factor in mass transport within inner bays. In Hakata Bay, the effect of shoreline change due to land reclamation on the flow in the bay has been studied in a uniform density flow field, but there are no examples of studies that consider the effect of river water.

The study first examines the transition of the coastline due to land reclamation in Hakata Bay from 1920 to 2016. A three-dimensional numerical simulation is then carried out to investigate the effect of topographic changes in Hakata Bay on the bay current, taking into account the density effect of fresh river water. The Princeton Ocean Model (POM) was used for the numerical simulations.

It was calculated that approximately 18.8 km² of land was reclaimed between 1920 and 2016, indicating significant modification of the coastal topography of the inner bay area during the post-war and high-economic growth periods. A comparison of the horizontal distribution of residual currents in the surface, middle, and bottom layers was conducted through numerical simulation under current and 1920 topography conditions. The results revealed that the flow conditions in the surface, middle, and bottom layers differ due to density depending on the topography. This indicates that topographical changes have affected the transport of materials within Hakata Bay. It is suggested that the alteration in topography has affected the transportation of materials in Hakata Bay.