Wataru Nishida

FORECASTING OF TIDAL CURRENT FOR THE ENVIRONMENTAL MANAGEMENT AT COASTAL AREA

The environmental management after human action is significant to eliminate and minimize the negative impacts on environment at developing area. In this study, the information distribution system of tidal current is proposed in order to support the environmental management in real time. Firstly, the numerical simulation model was developed to predict the temporal changes of tidal current and water stage at Isahaya Bay and Shimabara Bay, and the accuracy of predicted results was discussed in compared with the observed results. Following, the information system was built usingfree software. The predicted results of current by numerical simulation were distributed from thissystem by means of the internet in real time. This kind of system is likely to become very useful toolnot only for the water environmental management but also for the prevention of natural disastersaround the coastal area.

REVISION OF WATER QUALITY CLASSIFICATION BY BIOLOGICAL INDICES AND UTILIZATION OF ITS RESULT

River restoration work, or nature-friendly river work, is now under construction everywhere. In order to make it available for conservation and rehabilitation of desirable water environment, appropriate criteria of water environmental assessment should be established. In this paper, water quality has been investigated on a whole aspect, especially by the biological and ecological viewpoints.Attaining the final goal, extensive field survey has been carried out to estimate the impacts on water environment by river restoration work. Diagnosis of water environment using biological indices has been examined. Finally, dissemination about a necessity of water environmental management will be discussed, for example, installing an effective database system.

PREDICTION OF INFLUENCES ON THE TIDAL FLAT BY AN ENCLOSURE OF BAY

As the construction of sea dyke has come to finish on April 14, 1997, the 35.5 km2 area of original Isahaya Bay has been separated from sea, and will be changed to land in near future. It is considered that the spatial distribution of tidal flat around the Isahaya Bay is severely affected by the progress of reclamation project. Thus, numerical simulations were carried out in order to examine and evaluate the influences by an enclosure of bay. Calculated results show that the shoreline in the Isahaya Bay varies as the decrease of water exchange between inside and outside of the sea dyke. Moreover, because of the decreased velocity of current, deposition is occurred in front of the dyke. These results imply that the possibility of an appearance of tidal flat, and its area is influenced by the control of gates. It consequently indicates that adequate attention should be paid to preserve and create the tidal flat.