3D Numerical Simulation And Analysis Of The Transportation Of Suspended Sediment In The Huanghe Estuary

Yellow River Delta is located in the transitional zone of the river-sea interaction, where land and sea interact intensely. This area is not only the sink of the materials from Yellow River into the sea, but also the source of the Yellow River material dispersal system into the Bohai Sea. In order to systematically study on the transportation, transformation and the fate of the suspended sediment and fresh water from Yellow River into the sea, two synthetic surveys'data at the Huanghe estuary area are analyzed and discussed. Then the ECOMSED numerical model is applied to the Huanghe estuary. A 3D transportation simulation model with the orthogonal curvilinear grid which is based on the coastal line and terrain of Huanghe estuary is built up. With this model, the transportation processes of the fresh water and suspended sediment on the Huanghe estuary under low/high discharge condition are successfully simulated respectively. The following results are obtained throughout the work:1. Suspended sediment is transported towards the NW, the mouth of Yellow River will grow left-handed. This trend of developing is absolutely opposite with that of the abandoned Qingshuigou promontory which grew right-handed when it was in use.2. Two types of shear front resulting from the phase difference between the near shore and offshore tides appear off the river mouth over tidal cycle. As a result, two types of river-laden suspended sediment dispersal patterns form in the shear frontal zone. The fresh and highly turbid river effluents discharge to the sea during ebb tides and are transported northwestwards inside the shear front under the combined impacts of northward ebb currents, down-slope transport of hyperpycnal flow and confining action of shear front; after partially mixing with the ambient seawater the river effluents are then transported southeastwards outside the shear front along the flood currents, causing the intermittent increase in suspended sediment concentration and corresponding decrease in salinity outside the shear front. When the near-shore area turn to flood while off shore area is ebbing, the suspended sediment dispersal pattern is the opposite.3. Whether the river discharge is low or high, the fresh water disperse in the surface layer as the hypopycnal flow. When the river discharge is low, the salt water intrudes into the channel with the maximum distance about 5km, while the salt water mixes with fresh water during this course. When the river discharge turn high, the salt water only influenced the river mouth bar area, the water is laminated.4. The estuarine maximum turbidity zone occurs over tidal cycle but significant at the time when ebb and flow alternates and the tide speed is relatively little. It is located at the front of the saltwater wedge, which is on the river mouth bar area when river discharge is low while on the out side of river mouth bar when river discharge is high.