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

弱潮环境现代河口三角洲淤积发展之前的原始海岸架构是全新世海侵结束后形成的沙坝（堡）岛—潟湖体系。弱潮环境现代河口三角洲淤积发展的过程，就是近5～6千年来现代河流输沙淤积充填、改造沙坝（堡）岛—潟湖体系的过程。这个过程分两个阶段进行：首先缓慢地淤积充填坝（堡）后潟湖；然后“冲决”沙坝（堡）岛，向坝（堡）前海域发展。河流动力对沙坝（堡）岛的“冲决”行为，是实现两者间发展转变的标志。正是这种“冲决”作用，使河口的动力环境，从原来的主要受波浪和潮汐影响，转变为由河流动力作用控制。

The distlnctive characterlstlcs of the modem Pearl River delta formalion and develop-meat are divided phases, diversity and imbalance in spatial and temporal The delta was moving seaward gradually in a long period after the last Holocene glacial stage and the ancient drowned Pearl River estuary was predominated by tide The delta was expanding quickly since fluvial force was turned to be leading status about 2500 years ago. The sediment grain size was changing Ion-gitudinally from coarser to finer. As well as the finer sediment may be reworked and redistributed shoreward by tidal current nearby the river mouth And the fluvial-dominated delta is developed bv the mutual deposition reflected in the vertical direction According to the spatial difference of land-ocean interaction, the main body of the Pearl River delta which is the fluvial-dominated and protruding seaward is coupled with or concomitant with the estuaries and tide-dominated deltas which are adjoined to both sides of the main part like two wings.

珠江河口大系统主要由一正两负的亚系统构成。正亚系统指呈扇形向海凸伸的西、北江联合三角洲及其6个“河优型”分流河口；两负亚系统指分布于上述正亚系统两侧的、向陆凹入的虎门和崖门2个“潮优型”分流河口及其口内的潮汐水道。它们相向发展而具相依并存和耦合共生的特点，并且通过诸多的横向支汊进行沟通和联系。而每一单个河优型分流河口也同样存在河控和潮控耦合共生动力—沉积地貌体系，珠江三角洲沙田区的“潮灌潮排”农田水利体系与模式，是此种陆海耦合效应的生动表现。珠江河口治理应尊重、保护珠江河口系统大、小尺度的陆海架构关系及其有机联系，努力做到人与自然和谐共处。