Abstract
While recreational waterfront in urban area has been developed, chronical water quality degradation such as red tide and sewage water inflow has been occurred. Monitoring flow field around estuaries is required for appropriate water management. However, it is technically challenging to measure or calculate river discharge in estuaries due to complexity of its flow structure. This study discusses a method of measuring discharge of two-layered flow field by a stationary H-ADCP at Odaibakaihin park. Firstly, in a preliminary survey by an ADCP, a phase shift was observed in tidal velocity components of upper layer and lower layer in the vertical direction, which can be utilized to detect boundary of two layers and to determine thickness of the upper layer. The H-ADCP was settled upward in an angle of 1.5 degrees. Current profiles across the boundary were monitored, and river discharge of two-layered flow field was simultaneously calculated. In addition, a water quality meter combined with two pumping devices was vertically arrayed to observe water properties of multiple layers. Freshwater discharge could be quantified by relating flow rate and salinity of upper layer. This proposed monitoring method enables to monitor discharge of respective water layers and will expand more observatories effectively along analogous estuaries.
