Field Observations and Numerical Studies on Nearshore Currents in Shallow Water of Northern Taiwan Strait

Nearshore currents are important for material dispersion and sediment transport, yet, not well understood in shallow waters of Taiwan Strait where complicate nature forcing mechanisms such as tide, wind, and wave coexist. For enhancing the scientific impacts on Taiwan society, our study site includes a conservation area, the Guanxin algal reef, where is affected by coastal development (coastal jetty). The aim of the project is to study the effects from nature forcing of tide, monsoon wind (summer and winter), and wave and artificial effects due to construction of coastal jetty on the nearshore currents. Nearshore currents in the shallow water depth of 1 to 4 m in northern Taiwan Strait will be observed using ADCPs at sites close to and far from the coastal jetty. A numerical model-Delft 3D will be used to reconstruct the nearshore circulations. Preliminary results have shown that our modelled results agree well with the observational results. The verified model will be used to perform several idealized scenarios, i.e. with and without the nature forcing from wind, tide, and wave, and with and without artificial effects due to coastal structure. Specific scientific issues for studying include: 1. mechanisms driving nearshore currents in shallow waters of northern Taiwan Strait in summer and winter monsoon seasons. 2. Variation of currents in spring, neap, flood, and ebb tidal phases; 3. Understanding the tidal and residual currents in shallow waters; 4. Effects of coastal jetty on the nearshore currents; 5. Interaction between tidal-induced phases eddies and wave-induced eddies near the coastal jetty. Understanding of forcing mechanisms at the reef region is important to conserve the reef. Our study serves as a pioneer to investigate the nature forcing mechanisms that driving the shallow-water nearshore current at GuanXin algal-reef region.