Using the roughness height and manning number in hydrodynamic model to estimate the impact of intensive oyster aquaculture by floating & fixed rafts on water exchange with an application in Qinzhou Bay, China

Abstract

This study mainly addressed the methodology issue of how to model the hydrodynamic drag effects of aquaculture facilities and activities. Here, firstly, surface shear stress was determined by roughness height for characterizing the drag from floating aquaculture activities, while bottom shear stress was determined by the Manning number for characterizing the drag caused by bottom fixed aquaculture activities. Then, by taking Qinzhou Bay as a typical case, the two-dimensional model was established by integrating the multiple drag coefficients to quantify the impacts of the oyster cultivation activities on the water exchange capability (tidal prism and half-life time). The results showed that: (1) Cultivation activities would reduce the average tidal prism by 6.4% in Qinzhou Bay; (2) 10 averages longer day of half-life time was estimated to be resulting from the cultivation drag.