Research on the Morphological Evolution and Influencing Mechanism of Xiaolongmen Central Island by Cascade Hydropower Exploitation in the Middle Reaches of Jialing River

After the completion and operation of the Jialing River Hydropower Project, the central island evolution in the middle reaches of the Jialing River has been greatly influenced. The Xiaolongmen central island, which was less affected by human activities, was selected as the research object. Based on the Landsat historical remote sensing images and hydrological data of Jialing River for many years, the morphological evolution characteristics and influencing factors of the Xiaolongmen central island before the construction of the hydropower station in 2003 and 2005 and after the completion of the hydropower station in 2009-2017 were comparatively analyzed. The results showed that before the operation of the hydropower station, the Xiaolongmen central island was in a state of natural development and showed an overall increasing trend. After the operation of Fengyi Hydropower Station and Xiaolongmen Hydropower Station in 2008, the Xiaolongmen central island was generally declined, This was mainly due to the interception of a large amount of sediment by the upstream hydropower station, the strong scouring effect of water discharge from the hydropower station on the central island, and the comprehensive influence of the rise and fall of the surrounding water level on the coastline of the central island, which lead to the continuous retreat and shrinkage of the Xiaolongmen central island.