STUDY ON INFLUENCE OF BAIMAO SANDBANK CONTROL PROJECT IN SOUTHERN BRANCH OF THE YANGTZE RIVER ESTUARY, CHINA

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1 STUDY ON INFLUENCE OF BAIMAO SANDBANK CONTROL PROJECT IN SOUTHERN BRANCH OF THE YANGTZE RIVER ESTUARY, CHINA Xinzhou Zhan 1, Xipin Dou and Jinshan Zhan 3 The author estalishes the Yantze estuary D tidal and sediment mathematical model ased on the orthoonal curvilinear coordinate system. The erosion and siltation of enineerin section under the hydroloical conditions of flood season, dry season and the reat flood after the Sand control enineerin is calculated. Preliminarily expounds the correlation of Sand and Sand and the impact of Sand after the Sand control enineerin is implemented. Keywords: the Sand; the Sand; mathematical model; impact analysis INTRODUCTIONS The Sand waterway is located on the upper ride of the southern ranch of the Yantze River. The upper riverway is divided into southern and northern waterway of Sand ecause of the existence of the sand. The Sand waterway is located under the tidal current limit and influenced y the upstream runoff and downstream tidal. Bein one of three main naviation waterways from the Nanjin to Liuhe mouth, the channel s maintenance and development is influenced y the complex flow conditions, shoal erosion and siltation, inlet rise and decline. As a result, control enineerin is considered in the head Sand to stailize the current ood reime of Sand riverway. The Sand is a hue each located on the southern shore of lower sement of southern ranch. Bounded y the south ate port in Chonmin, the west part is called upper Sand, the east part is called the lower Sand(Fiure. 1). The upper Sand is the north oundary of lower sement of North Sand waterway, the lower Sand is the north shore wall of Sorth ranch lower sement of Yantze River s mainstream channel. The pattern and trend of Sand directly influences the trend of lower sement of Sorth ranch of Yantze River s mainstream channel. Hence, the research of the correlation of Sand and Sand and the impact of Sand after the Sand control enineerin is implemented is needed. Fiure. 1 the pattern of multilevel ifurcated channel TIDAL AND SEDIMENT MOVEMENT FUNDAMENTAL EQUATION Tidal Movement Fundamental Equation Under the Cartesian coordinate system -, the D tidal movement fundamental equation is as follow: 1 Nanjin Hydraulics Research Institute, Key La of Port, Waterway and Sedimentation Enineerin of the Ministry of Transport, 3 Guanzhou Road, Nanjin, Jiansu, 19, China Nanjin Hydraulics Research Institute, Key La of Port, Waterway and Sedimentation Enineerin of the Ministry of Transport, 3 Guanzhou Road, Nanjin, Jiansu, 19, China 3 Nanjin Hydraulics Research Institute, Key La of Port, Waterway and Sedimentation Enineerin of the Ministry of Transport, 3 Guanzhou Road, Nanjin, Jiansu, 19, China 1

2 COASTAL ENGINEERING 1 ς ( Hu ) + ( Hv ) = (1) u u u v u uv + v u u v ς 1 A fv + = E C H B () v u v v v uv + u v u v ς 1 B fu + = E + C H Where, A = ( u ) + ( v ) / B v u ; = ( ) ( ) / ; A (3) = x + y ; = x + y. u and v are the flow velocity components on the direction of -; is water lever, H is total water depth; C is Chezy coefficient,, are Lami coefficient; E is viscosity coefficient of flow turulence. Sediment Movement Fundamental Equation Under the Cartesian coordinate system, Dou Guoren d suspended sediment transport equation is as follow: ( HS ) 1 ( HuS) ( HvS) αω ( S S ) = Where S is vertical averae sediment concentration; α is an undetermined coefficient and is defined y validation calculation; ω is sediment settlin velocity, and equals to flocculation settlin velocity under the flocculation condition; S is sediment carryin capaility of the flow, with the Dou Guoren formula, can e expressed under the comined action of tidal and wave as follow: S ( + ) 3/ u v H (5) γ γ ω ω γγ s W = α + β s C H HT Where γ and γ S are volume-weiht of water and sediment particle, H w and T are heiht and period. Accordin to the data otained in many sea areas,.3 f is wave dra coefficient. Chezy coefficient is defined y Mannin formula, w the surface rouhness coefficient. (4) averae wave α =, β =.4 f w, Bed Load Sediment Transport Fundamental Equation Dou Guoren ed load unalance sediment transport fundamental equation is as follow: x y ( HN) ( HNu) ( HNv) = ( + + αω N N ) C 1/6 = (1 / nh ), n is Where N is ed load sediment concentration in unit volume; α is ed load sedimentation coefficient, ω is ed load particle settlin velocity; N is defined as follow: N q Hv / (6) = (7) Where q is ed load sediment transport aility in the condition of unit time and unit width, defined y Dou Guoren formula.

3 COASTAL ENGINEERING 1 3 Rivered Deformation Fundamental Equation Rivered deformation equation caused y suspended load is as follow: S γ = αω( S S ) Where is siltin and scourin thickness caused y suspended load. S Rivered deformation equation caused y ed load is as follow: γ = αω ( N N ) Where is siltin and scourin thickness caused y ed load. Siltin and scourin thickness caused y suspended load and ed load is as follow: (8) (9) S = S + (1) THE CALIBRATION AND VALIDATION OF TIDAL AND SEDIMENT MATHEMATICAL MODEL The Calculation Area and Calculation Grid Accordin to the research contents and mission requirements, and in order to satisfy the water flow movement similarity, this mathematical model calculation scope is west to Jianyin, east to 13 east lonitude, south to 9 7 ' north latitude, north to 3 15' north latitude, includin the waters of the Yantze estuary and the Hanzhou ay model. Fiure is the calculation scope of the mathematical model. Because of the shape of Yantze estuary oundary is very complex, the model uses orthoonal curvilinear rid which fits the oundary of the river as the computin rid, and refines the rid in enineerin section, the rid numer is =168156, the scale is etween 1~m. Fiure 3 is the calculation rid of the mathematical model. Fiure. the calculation scope of the mathematical model. Fiure 3. the calculation rid of the mathematical model.

4 4 COASTAL ENGINEERING 1 Caliration and Validation of Tidal Mathematical Model The control tide level of the open oundary is provided y Hohai University calculatin the east China sea mock- up model, the upstream open oundary is provided y the Yantze river scientific research institute of the Chanjian Water Resources Committee calculatin the Jianyin flow process. The upstream sediment concentration hyroraph of the open oundary is calculated y the 1d tidal and sediment mathematical model, the sediment concentration of the off-sea oundary is.1k/m³.usin the excess water depth method, continuously fixin water oundaries waterfront and automatically reconizes the oundary accordin to the chane of water level. When the upstream and off-sea oundary is iven, parameters deued throuh caliration, accordin to the linear interpolation, the rouhness from coast to upstream is defined as n = / H ~. +.1 / H, turulence viscous coefficient υ t is 3m /s, the computation time step of tide mathematical model is 4 seconds. The time step of total load mathematical model is seconds, the rouhness is the same as the tide 3 mathematical model. The sediment particle volume-weiht γ = 65 k / m, suspended load dry s 3 3 volume-weiht is γ = 75 k / m, the ed load dry volume-weiht is γ = 1 k / m. The sediment s o particle of the upper Gaoqiao water area is not flocculated, considered as d 5 =.1mm, water temperature is hih in the flood season, settlin velocity ω =.1 m/ s; water temperature is low in the dry season, settlin velocity ω =.8 m/ s. The sediment particle settlin velocity of the lower Gaoqiao water area differs with the chaned salinity and temperature in the flood and dry season, hence the settlin velocity of suspended particle is eneralized to.8m/s~.7m/s. The ed load sediment particles d =.1mm on the each face, d =.14mm at the ottom of slot. 5 5 ENGINEERING PLAN AND TIDAL CALCULATION AND THE ANALYSIS OF THE RESULTS Accordin to the arranement of enineerin plan, with the calculatin conditions of sprin tide of flood and dry season and 98 reat flood, the enineerin reion terrain is latest measured in March 1, usin the validated and calirated Yantze estuary tidal mathematical model, researches the flow field chanes efore and after sand enineerin plan is implemented, analyses the enineerin plan's impact on the sand. Project Scheme Accordin to the main prolems of sand waterway, comined with the future developin trend, the reulation project layout plans of Sand waterway are defined, includin the recommended plan (Scheme Ⅰ), the elected plan(scheme Ⅱ) and the added plan(scheme Ⅲ). Three layout plans are as follow: Scheme Ⅰ Scheme Ⅱ Scheme Ⅲ Fiure 4. The schemes of Control Project. Sediment Calculation and Analysis Sediment calculation conditions. Accordin to the enineerin project arranement, uses hydroloic condition of flood season, dry season and the 98 reat flood as calculation condition, researches the siltin and scourin variation of this stream sement. The calculatin roups are shown in tale 1.

5 COASTAL ENGINEERING 1 5 Tale 1 The calculatin roups Project Research section Calculation hydroloical conditions Scheme Ⅰ Sand- Sand One month of flood season, dry season, reat flood Scheme Ⅱ Sand- Sand One month of flood season, dry season, reat flood Scheme Ⅲ Sand- Sand One month of flood season, dry season, reat flood Analysis of the results. After the project is implemented, the chanes of hydrodynamic conditions lead to the correspondin chanes of river ed s siltin and scourin. In order to analysis the impact on the chanes of the river ed s siltin and scourin after each enineerin plan is implemented, the impact of project on the siltin and scourin of the stream sement is ot after usin the calculation results of each plan s siltin and scourin minus the ones efore the project is implemented. - - Fiure5. Toporaphy chane after the implementation of Control Project (flood season) Fiure6. Toporaphy chane after the implementation of Control Project (dry season) Fiure7. Toporaphy chane after the implementation of Control Project (reat flood).

6 6 COASTAL ENGINEERING 1 The calculation results show that the project has limited influence on the siltin and scourin rane of the river ed and almost no influence on the river ed near the Sand after the enineerin plan is implemented. The siltin and scourin caused y the project is almost within.7m. CONCLUSION The preliminary conclusion is ot throuh the research of Yantze estuary D tidal sediment mathematical model as follow: 1. For the last years, influenced y continuous floods from the Yantze River, sandank has tended to move down year y year and the area of sandank ody has ecome less and less. Therefore, control works shall e undertaken immediately to protect and maintain sandank. To maintain the staility of sandank ody is important to keep the staility of the ood river pattern on the lower side of the southern ranch.. Accordin to the calculations in one month flood season, dry season and flood, after the implementation of the control project, the scour and sedimentation in local parts of the project has relatively i chanes which is asically within 1.; it is slihtly silted on sandank sand ody and the sheltered zone in the Yuuchi dam of sandank control project is silted to.1~.9m thick, which is helpful for the staility of the pattern of sandank sand ody; for the southern channel and northern channel of sandank, the upper side is scoured, the middle part is silted and the southern side of sandank s end is scoured; sandank is slihtly scoured in its southern side and end of upper side with a scourin rane within.55m and.35m respectively. 3. Analysis on the scour-and-fill of landform caused y one month flood season, dry season and flood and other conditions indicates that the implementation of all plannin has limited influence on the rivered in the matter of scour-and-fill which is mainly concentrated in the project areas with a rane within.7m, asically havin no impact on the scour-and-fill of the rivereds near sandank. The enineerin plan will not have an ovious impact on sand after the project is implemented throuh comprehensive analysis of flow field and sediment erosion and deposition chanes ACKNOWLEDGMENTS The research work is supported y the Pulic Welfare Scientific Research Project of Ministry of Water Resources No and National Natural Science Foundation No REFERENCES Xia Yimin,Yuan Wenzhi(1998): Study on reulation works of the - sandank sement of the Yantze estuary, Ocean Enineerin,Vol.16 No4, pp