A Study on Impacts of the Isahaya Bay Reclamation Project on Tide and Tidal Current in Ariake Bay

Flowage Analysis with Three-dimensional Numerical Model and Observational Data

Abstract

To clarify the impacts on tide and tidal current in Ariake Bay by the dyke of the Isahaya Reclamation Project, it have been carried for investigating with using two approaches:(1) by analysis of observational data at tide stations and (2) by three-dimensional numerical model. Model output indicate that the 0.8-1.5% decrease of the spring tidal range in outside area of Isahaya Bay is caused by the Isahaya dyke. On the other hand, it is found that there areno changes on tidal conditions in Ariake Bay due to the Isahaya Reclamation Project from consideration on observational data. Although the about 5% decrease of tidal currents off shore of Shimabara peninsula is assumed to be influenced by the Isahaya dyke according to the results from three-dimensional numerical analysis, it is confirmed that tidal currents in outside area of Isahaya Bay illustrates no difference due to the Isahaya Reclamation Project from comparison of observational data before and after construction of Isahaya reclamation dyke; that is, tidal currents in Ariake Bay depend on observation points or water depth. Therefore, it is concluded that tide and tidal current in Ariake Bay is not primarily affected by the dyke of the Isahaya Reclamation Project.