Patterns of sediment transport pathways on a headland bay beach-Nanwan Beach, South China: A case study

Embayed beaches bounded by headlands, headland bay beaches, are a common feature along the coast of southern China. The patterns of sediment transport pathways in these beaches are important for understanding changes in beach and nearshore geomorphology that are a response to different wave energy conditions. Nanwan Beach in southern China is characterized by a large seasonal variation of incident waves. In this study, sediment samples and a series of beach profiles from Nanwan Beach are examined to determine spatial changes in sediment transport pathways. Empirical orthogonal function analysis of the profile data indicates that the variation of sediment transport occurs in two distinct modes. The first mode is related to seasonal changes in cross-shore sediment transport with associated alongshore sediment transport. The trend of sediment transport is seaward in winter and landward in summer. The second mode is onshore-offshore sediment exchange, which occurs in the intertidal zone in summer and in the swash zone in winter. Moreover, grain size trend analysis of sediment samples suggests that sediment transport in the nearshore zone is predominantly in the northwesterly direction because of southeast incidence waves in winter, with Nanwan Bay opening to the south. The sediment transport pathways are to the north in summer from the influence of typhoons.