| Popis: |
The large salinity variation in estuaries may create a challenging environment for the ecological system. Changes in the balance between freshwater and saltwater can lead to the loss of species. Therefore, investigation of salinity intrusion in estuaries is important, both in terms of understanding the complex balance between the fluvial and tidal processes that affect the salinity intrusion within the estuary, and also in terms of formulating effective policies for sustainable development in coastal regions. Understanding the mechanisms that affect the salinity intrusion has implications for management of estuaries. A clear understanding of the factors affecting the salinity intrusion in estuaries is thus required for the long-time period of hydrological conditions. The Ota Estuary encompasses the branched section of the Old Ota River and the Ota Diversion Channel about 9 km upstream from the estuary mouth. The present study attempts to identify the salinity intrusion through the Ota Diversion Channel that is a shallow tidally-dominated channel with gates. The existence of the Gion Gates at the upstream border which restricts the freshwater runoff is an important feature of Ota Diversion Channel. This study consists of the field observations and numerical simulations. This thesis addresses the variability of salinity flux, flushing time, salinity intrusion length, stratification and estuarine circulation in the Ota Diversion Channel under the different estuarine forces (freshwater, tides, etc.).…… |
