Relationship between the morphological evolution of the river mouth bar and fluvial input in the Modaomen Estuary

River mouth bars commonly exist in estuaries and are important for flood control, estuarine ecology, and the navigation of estuarine areas. The Modaomen Estuary is a river-dominated estuary in the Pearl River Delta and has a typical river mouth bar. Here, hydrologic and bathymetric datasets that span 2000–2011 are used to analyze the relationship between the fluvial input of river discharge and sediment load and the evolution of the river mouth bar. The results show that the eastern and western channels have notably extended seaward since 2000. The evolution rates exhibit distinct asymmetry, with the seaward extension rate of the eastern channel being approximately 1.6 times greater than that of the western channel. The upstream bar face and bar back of the center mouth bar have been eroded, and intensive human activities have significantly affected the evolution of the center mouth bar. The center mouth bar's apex has consistently moved seaward from 2000 to 2011. River discharge (especially during extreme river floods), rather than sediment load, has played a more vital role in the development of the bifurcation channels and the center mouth bar. An empirical relationship between the bar-apex displacement rates and dominant discharge is obtained based on the observations, indicating that greater river discharge and longer duration will move the bar apex further seaward. The bar apex's displacement during the extreme river floods of "2005.6" and "2008.6" was 133.6 m and 99.4 m, respectively.