黄河自花园口至河口常称为下游,自古以来历经多次大改道。每次改道后,由于黄河流域来沙多,随着堤防的建成和泛滥受到限制,大量泥沙在堤间堆积,使河道比降增大,最终形成地上河或悬河。又由于河道尾闾注入的黄海或渤海都是弱潮海域,大量泥沙在口门附近落淤,使河口不断延伸,引起溯 The Yellow River from the garden mouth to the mouth often known as the downstream, since ancient times after many major diversions. After each diversion, due to the sand in the Yellow River basin, with the completion and flooding of the embankment is restricted, a large amount of sediment accumulates between the embankments, increasing the ratio of river courses and eventually forming the above-ground river or hanging river. In addition, the Yellow Sea or the Bohai Sea injected into the tail of the river channel are all weak-tide waters. A large amount of sediment is silted in the vicinity of the doorway so that the estuary extends continuously and leads to the retrogression