磨刀门河口是珠江八大口门中输水输沙量最大的河口,口外拦门沙发育,其泄洪安全一直是磨刀门口门治理的头等大事。本文基于2003年洪季磨刀门河口拦门沙水域水文观测资料及近年典型洪枯季河床地形资料,分析了河口拦门沙排洪动力特征及拦门沙典型地貌单元对洪水的响应规律。研究结果表明:磨刀门拦门沙水域洪水季节水体分层明显,表现为浮力射流;外海高盐水被拦门沙阻挡,无法越过拦门沙向里侵入;拦门沙对洪水的壅水作用主要表现为低水位的壅高,灯笼山站与大横琴高潮位及低潮位水位差均和马口流量有较好的线性正相关关系。由于洪水季节磨刀门河口径流占显著优势,洪水成为拦门沙演变的主要动力,通过拦门沙典型地貌单元年际、年内演变特征分析发现,在洪水的冲决下拦门沙东、西汊得到较快发展,其中东汊的冲决效果更强烈,当洪水来临时东汊成为排洪的重要通道;洪水对交杯四沙冲刷作用较明显,特别是交杯四沙内侧南北向并岸沙堤易被洪水冲开;受洪水冲刷影响,拦门沙西汊前缘次一级分汊体系的雏形已经形成。 Modaomen estuary is the largest port in the Pearl River estuary eight gates of water and sediment transport, estuary sand barrier development, the flood safety has always been the first priority of the knife gate. In this paper, based on the hydrological data from the Sando Gate at the estuary of the flood season in 2003 and the riverbed topography data during the flood season in recent years, this paper analyzes the dynamic characteristics of the discharge of sand at the estuary and the response law of the sandform topography to the flood. The results show that the glacial sand of Debao Gate is obviously delaminated during the flood season, showing as a buoyant jet. The high saltwater in the outer sea is blocked by the sand bar and can not penetrate into the sand in the barricade. Mainly for the low water level 壅 high, Lantern Hill Station and Grand Hengqin high and low tide level water level and the horse mouth flow has a good linear positive correlation. Due to the significant advantage of the runoff at the Modaomen River mouth during the flood season, floods have become the main driving force for the evolution of barren sandstorms. Based on the analysis of the interannual and evolutionary features of typical sandstone topographic units in the barren sand area, The rapid development of the East Lake, the rushing effect is more intense, when the flood comes Dongjian become an important channel for flood discharge; floods on the Cup four Shes scouring effect is more obvious, especially the cross cup sand south-north and shore shore sand Embankment easily washed away by floods; the rudiment of the first sub-system of Shahejie Bay front bar has been formed.