Numerical Simulation Of Flow And Sediment Transport In Shenzhen River And Bay And Flood Control Scheme

Shenzhen River is the boundary river between Shenzhen and Hong Kong. Withthe completion of the1st and2nd part of Shenzhen and Hong Kong’s joint ShenzhenRiver Regulation Project, the rive bed suffered serious sediment deposition, whichhas greatly reduced the flood control capacity of the Shenzhen River. It has importantguiding significance for the flood control and the pollution control of water andsediment in Shenzhen River, with the study on the hydraulics, sediment transportationand morphological change of the area, based on the hydrodynamic and sedimenttransport numerical model.Analysis with all previous data of Shenzhen River bed topography shows that, inrecent years, the whole reach tends to the deposition. Deposition is dominated inabout47%sections of the whole river area;41%area belongs to the dynamicequilibrium; and12%left is unstable areas. The total amount of sludge in the sectionbetween Luohu and Shenzhen River mouth was3million cubic meters just after theflood season of2009. Analysis with the combination of hydrological data shows that,runoff plays an important role in the river bed’s erosion and deposition. In the dryseason, with small runoff, the increase of the runoff leads to more deposition of theriver bed. Otherwise, in the wet season, with large runoff, the increase of the runoffleads to the erosion of the river bed. The rive bed is depositing overall.A two-dimensional hydrodynamic and sediment transport numerical model forShenzhen River and Shenzhen Bay was set up using the domain decompositiontechnique in Delft3D model, which decomposed the study area into two computingareas with different grid size for coupling calculation. The verifications in wet seasonand dry season shows that, the averaged errors of the high/low tidal level, flood/ebbtide current velocity, peak flow and sediment concentration are less than0.10m,0.14m/s,75.02m~3/s and0.021kg/m~3, respectively; and both the flow field andmorphological change are basically reasonable, the absolute and relative errors ofmorphological change are2.30cm and23.7%. So the model can be applied for simulating the hydraulics and sediment transportation of the Shenzhen River and Bay.Based on the verification of flow and sediment transport, a measured floodingprocess from Jun.11to Jun.16in2008is verified. The errors of peak flood level anddischarge are less than0.15m and5.5%, respectively. Based on the flood verification,the present flood control capacity of Shenzhen River and the effect of two groups ofdredging schemes are studied by model. The computation results show that, the peakflood levels of Wutong and Buji River Mouth are0.659m,0.738m higher than thedesign water levels under20-year flood, respectively; and0.836m,0.928m higherunder50-year flood, respectively. It shows that, the flood control capacity ofShenzhen River is much lower than50-year flood control standard and even lowerthan20-year standard in upper section. When averagely dredging2.0m from the bed,the flood control capacity of Wutong River Mouth can reach50-year flood controlstandard, and the peak flood level of Buji River Mouth is0.026m higher than thedesign water level, which is close to50-year flood control standard.