南渡江三角洲海岸可分为东部废弃侵蚀岸。北部混沙转运岸和西部淤涨堆积岸等三个岸段。北部岸段为了连接东、西部岸段，存在大规模的、有节奏的沿岸泥沙向西和向岸转运及其相应的岸滩运动现象，泥沙主要来自南渡江干流河口及其以东的废弃侵蚀岸。文中还结合对北部岸段河口和沿岸泥沙转运规律的分析，讨论了波浪优势型河口三角洲特征及其堡岛海岸的形态、动态和泥沙来源以及人类活动对该岸段的影响等问题。

This paper analysed the main factors of the coastal formation in South China, i.e. the geological structures, the geographical conditions of the mainland coast, the raise of the sea-level during Holocene, the tide, the wave, the longshore drift and so on. The coast in South China is characterized by the pattern of barrier-lagoon (or bay), because the tide range is small and the sediment transported by wave is rather strong. The mud-sand of most part of the barriers was derived from inner shelf, and moved landward with sea-level rise in Holocene. The author described in full details of the morphology about the two patterns of harbour-coasts (i. e. sub-merged valley and barrier-lagoon) The characteristics of the harbour of barrier-dagoon are as follows: 1. A harbour with the ha rrier-lagoon is commonly independent from the adjacent coastai systems; 2. Either the pluvial-alluvial terraces and the erosion platforms or the hills always lie at the back of the harrier-lagoon (or bay) systems; 3. During the Holocene, the barriers had evolved continuously by retreat, progradation and return. That correspondingly caused the changes of the other morphology, such as the area of lagoon. the mud flat, the tidal inlet and its sand bodies; 4. The foreshorelines of most barriers have tended to the logarithmic spiral plan shape; 5. The morphodynamics of beach may be divided into three sections; 6. The throat-position of the tidal inlet is always situated in the apexof Z-shaped headl-and-bay and is generally stable.

Based oDthe observed data in l982-1985 at Shuidong Bay area, west Guangdong Province, the morphodynamic processes of tidal inlet and ebb-tidal deltainthe barrier-lagoon system are presented, including the dynamic features of tides and in the tidal inlet. the regional dyanmics and longshore sedimeot transport in the ebb-tidal delta, the genesis of the entrance bar, the recent erosion and deposition in the ebb-tidal delta and so on. The paper attempts to answer two questions, i. e., the stability of the tidal in let and the feasibility of dredging on the entrance bar for the course of Shuidong Harbour The reslts show that the stability of the tidal inlet is ideal and that dredging action on the entrance bar may be suc-cessful if dredging is deep enough and the course position reasonable