The erosion and sedimentation at the triple-branches of the Jingjiang River will increase after the Three Georges Project. This will affect the flow and sediment relationship between the Jingjiang River and Dongting Lake, impacting flood situations. A river network sedimentation model was used to simulate the changes, showing that maximum erosion will occur around 40 years after the project. This information can help in understanding flood protection and water resource management in the area.