We examined characteristics of material transport and a tidal front formation in a semi-enclosed bay, Korea, based on numerical experiment results. Pollutant diffusion resulted in a relatively high concentration in the northwest part of the bay compared to the other area, because of inactive flow and topographic factor. The diffusion area of pollutant appeared 3.25km2 in the spring, 4.62km2 in the summer, 3.25km2 in the autumn and 2.35km2 in the winter, respectively. Tidal fronts, which is defined by log(H/U3) turned out to be large at the east and south channels, comparing to the results of a particle tracking method. Thus, we realized that the flow is almost stagnant at the northwest part of the bay, and as a result, oxygen-deficient water mass appeared. The particles, which are defined as pollutant or material, moved more toward the east mouth in the summer whereas they moved more toward the south mouth in the winter, compared to those cases of no wind forcing.