Abstract: The Dongdongting Lake Ouchi River East Branch Delta is the fastest developed beach in Dongting Lake in past 100 years. In order to analyze the erosion and deposition process of the Ouchi River East Branch Delta, predict its future development trend, and provide data support for the utilization of the East Dongting Lake beach and water and sediment management, this article uses remote sensing technology and combines years of water and sediment data to conduct a spatiotemporal analysis of the erosion and deposition of the Ouchi River East Branch Delta from 1967 to 2023 in past 55 years from three aspects: beach area, river channel changes, and vegetation changes. Research has shown that the 1960s to 1980s were a period of rapid expansion in the area of the eastern branch of the Ouchi River delta, with an average annual growth rate of 6.48 km². In the 1990s, the growth rate slowed down, with an average annual increase of 0.94 km². After the operation of the Three Gorges Reservoir in 2003, the average annual increase in area decreased to 0.13 km². Due to the influence of the hydrological environment inside the lake, the river channels in the delta first extend northeast and then turn southwest to form an “inverted U”-shaped reverse erosion and deposition. Sediments accumulate along both sides of the river channel, forming a slope shaped sandbar with high near the river channel and low far from it. Since 2003, the area of reeds on the sandbar has increased while the area of lake grass has decreased, indicating that the expansion of the sandbar area is tending to stop, but siltation is still continuing.

Key words: Dongting Lake, beach expansion, remote sensing technology, Ouchi River Delta