Swan Island, located in Jingjiang reach of the Yangtze River, is a relatively independent semi-closed natural wetland landscape group with a length of 2 1km and an area of 70.807 square kilometers, including a water area of 20 square kilometers, where finless porpoises and other national protected species live. Due to the twists and turns of the river, the upstream sediment is easy to deposit. Up to now, the plains on both sides of rivers in this area are generally lower than the water level of the Yangtze River, showing the trend of "hanging the river on the ground".
The old course of Swan Island Yangtze River belongs to Hubei Yangtze River Swan Island Baiji Dolphin National Nature Reserve, which is located in the southern edge of Jianghan Plain. Due to the low-lying terrain and the swinging and scouring of water, the Yangtze River has formed a unique "nine-bend ileum" landscape in Jingjiang, leaving many old rivers after natural or artificial cutting and straightening.
The old road of Swan Island was formed by natural bending of 1972. It encircles Swan Island in a crescent shape, and it is oval. It is connected with xiaohe town in the southeast in dry season, and it is in a peninsula shape, but it is completely surrounded by the old road in flood season. Tianezhou wetland has the lowest water surface of the old road, and the shoal of the old road gradually increases to the river bank. The annual river flood, coupled with the top support of Dongting Lake, reduces the velocity and silts up, forming a large reed swamp wetland.