Author(s): T. T. Tran; Hong Son Truong; H. T. Le

Linked Author(s):

Keywords: Headland; Tidal inlet; Field data collection; Numerical model; Satellite imagery

Abstract: Tien Chau tidal inlets providing only access from the Xuan Dai Bay to the Tien Chau Harbor is a major waterway of Tuy An district, Phu Yen province, Vietnam. The Tien Chau tidal inlets are located in a tropical monsoon region, with a low-meso tidal range, a medium wave height, and an insubstantial river inputs. Moreover, the Tien Chau tidal inlet is anchored directly next to a pronounced bedrock headland and is bordered on its opposite side by a sandy spit. The downdrift barrier island is absent. These features make the Tien Chau Tidal inlet differ markedly from those which are not attached to headlands or occur along straight barrier shorelines, such as those observed on the United States' East Coast and Gulf Coast, the coasts of Australia, Canada, or West Germany, and similar to those on the northeast coast of the New Zealand, but without monsoon climate. Despite its important role, the Tien Chau tidal inlet is filling with sediment and the sandy spit is fluctuating landward and seaward. The unpredictable currents, waves, and shifting of the updrift barrier make it difficult for ships to travel through the inlet and have negative influences on the local environment and fishery resources. In this study, a comprehensive data set of waves, tide, river flow, and topography were collected and measured at different sites across this environment. The geomorphology of the Tien Chau tidal inlet was assessed using measured data in combination with satellite imagery, aerial photographs, and topographic maps. From this, the main morphological characteristics of the system were studied. It is suggested that the headland offers a natural protective barrier and block incoming waves from Southwest monsoon. As a result, the sandy spit fluctuates significantly during the flood season coincide with the Northeast monsoon. Moreover, although average river discharge is low, a strong relationship between the width of the inlet throat and river inputs is indicated, suggesting the important role of the river input on the stability of the tidal inlet, especially during flooding from the upstream river. Furthermore, it is also suggested that the hydrodynamics of the flood tidal delta is similar to that of a compound channel. Additionally, the measured data sets were used to validate and calibrate the performance of a schematized coupled hydrodynamic and wave model for the Tien Chau Tidal inlet, built in the Delft3D model system. The good agreement between observed and modeled waves and flow, with nearly default parameter settings confirms this model a tool to study hydrodynamics and associated sediment transport, and to propose better solutions to manage the Tien Chau coastal and estuarine systems.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022226

Year: 2022