The morphological evolution of estuarine areas occurs at multiple time scales. The Modaomen Estuary (ME) in Pearl River Delta (PRD), China, is one of the main outlets of freshwater and sediment into the South China Sea. A long-term morphodynamic model based on TELEMAC numerical modeling system was applied to the ME to explore input reduction of the river boundary condition, discuss the effect of wave, and analyze the classification of the ME and its long-term morphodynamic equilibrium. Four input reduction scenarios were tested in the model: annual average runoff discharge, bed formation discharge, hourly water levels in a representative year, and combined seasonal discharge (flood season, intermediate season and dry season). The model results show that the general patterns of erosion and deposition at the mouth bar and channels are represented reasonably well when combined seasonal river discharge is used. Sediment was silted onto the external slope of the central mouth bar due to runoff, and was transported landward and westward under the effect of waves. Based on the modeled long-term morphological evolution results, the general morphological pattern can be reproduced under the control of runoff and tides without considering the effect of waves, showing that classification of the ME is runoff dominant. At the seasonal scale, morphology is adjusted through silting in the flood and intermediate seasons and scouring in the dry season. At the interannual scale, from 1994 to 2017, the net volume changes decreased gradually, indicating that erosion and deposition tend to be balanced in the ME. The results of this study provide a valuable basis for long-term modeling and estuarine regulation. |
