The Administration and Geomorphological Evolution in Modaomen River Mouth of Zhujiang Estuary

About one- third of runoff and stream load from Zhujiang Delta is transported into sea area through river mouth. Therefore administration of is of a decisive position to ensure flood discharge safety in Zhujiang Delta. A program of dredging river mouth has been carried out essentially from 1984 to 1995 and acquired obvious effects for discharging flood,shipping,drainage and reclamation. During recent 20 years, shallow estuary becameModaomen deltain which area of plain accounts for 77%. The river mouth is extending to sea area outside estuary,and thus a Modaomen submerged deltais forming. The runoff dynamics is still dominant but influence of hydrodynamics such as coastal current,storm tide and wave becomes stronger. Due to changes of depositional basis, hydrodynamics condition,silt movement and sedimentation, the submerged deltamay transform from runoff-dominated type to runoff- tidal dominated type,and extending tendency of delta may be westward. The arrangement direction of dredging lines in future should be inclined to south -west and to preserve situation like a large bell.