Proceedings of the 22nd IAHR-APD Congress 2020, Sapporo, Japan

Numerical analysis on impacts of the project of north branch narrowing on sediment distribution
GUO CHUANSHENG (China Institute of Water Resources and Hydropower Research, P. R. China), TANG LIQUN (IWHR, P. R. China), WANG YUHAI (IWHR, P. R. China), ZHAO HUIMING (IWHR, P. R. China)
121°00′RESULT AND DISCUSSION

Model Verification

The north branch of Yangtze estuary starts in the west

The model validation was performed using the measured

121°00′121°30′32°00′

Jiangsu
122°00′Island, to the estuary Lianxinggang(LXG) in the east.

water level, flow velocity, and sediment concentration ofdata in the corresponding period were collected fromchannel of Yangtze estuary. Since 18th century, thenational or local basic tide stations. These data were usedmainstream of Yangtze River has diverted to the south

to validate the model, and some results are illustrated in

gradually decreased, causing an overall appearance ofsedimentation and shrinkage in the north branch.
ShanghaiandJiangsu

Province

implementedamiddling narrowing project in the north branch ofJiangsu

large and small tides in December 2012. The tide level

With a total length of 83 km, it is a first-class branchbranch, hence the runoff into the north branch has

Latitude(°)

32°00′

from Chongtou(CT), the western end of Chongming

122°00′

Ch
on

gm
ing

SSC(kg/m³)

Isla
nd

32°30′

Ch
on

gm
ing

Isla
nd
Shanghai

32°30′
121°00′Figure 2. Some simulation results are illustrated in

121°30′122°00′Longitude(°) project(a) before narrowing

Shanghai
121°00′121°30′122°00′32°00′

Figure 3 and Figure 4. The results indicated that the121°00′121°30′122°00′

Jiangsu(a) before narrowing project

simulated tide level, flow velocity and direction, and121°00′

121°30′122°00′32°00′

sediment concentration had good consistency with theLatitude(°)

Introduction

121°30′

Chon

gm
ing

Jiangsumeasured data, which could truly represent the flood-ebb

SSC(kg/m³)

Isla
nd32°30′

fluctuations of the north branch and indicate theYangtze estuary.
Based on the two-dimensional mathematical model of

Chocharacteristics of tide movement in Yangtze estuary.

ng

ming

Is landShanghai
32°30′
121°00′tidal current and sediment, a simulation model of

121°30′122°00′Longitude(°)

sediment transport in Yangtze estuary region has been
established in this paper, and the changes in sediment

121°00′Figure 2. Tide level validation.

transport in the north branch after the implementationofthemiddlingnarrowingproject

havebeen

Flood tide peak flow (104 m3/s)
BeforeAfternarrowing
narrowing
Changeproject
project

122°00′32°00′

Jiangsu
Qinglonggang A1ng

uth32°30′

North Branch Narrowing Areabranch

Is landA7
A8A9

SpringChongtoutide
section
Neaptide
SpringSantiaogang
tide
section
Neaptide

Ebb tide peak flow (104 m3/s)
BeforeAfternarrowing
narrowing
Changeproject
project

1.437

1.605

11.72%

0.73

0.566

-15.05%

0.768

0.790

2.94%

0.42

0.336

-3.87%

6.241

5.812

-6.87%

1.05

3.170

3.43%

3.176

3.058

-3.70%

0.59

1.727

0.85%

Chongtou
sectionSantiaogang
sectionSpring
tide
Neap
tide
Springtide
Neaptide

Ebb tide peak sediment concentration(104 kg/s)
BeforeAfternarrowingnarrowing
Changeproject
project

0.872

0.742

-14.84%

1.126

0.958

-14.86%

0.848

0.720

-15.01%

0.434

0.357

-17.54%

1.795

1.894

5.52%

3.081

2.747

-10.83%

1.746

1.585

-9.17%

1.166

1.002

-14.01%

 (1) The middling narrowing project did not change the flow pattern of flood/ebb tide, and the flow characteristics offlood/ebb tide in the south and north branches were basically unchanged.

32°30′

Ch Nort
h Ch
ang
ann
xin
elSoguthChannelShanghaichannel of north branch was narrowed and the dynamic force of tide intrusion was diminished, leading to them³
m³

m³m³

decline in the high tide level of spring tide in the north branch, which benefited the coastal protection against thetide. Meanwhile, the increase in flow velocity and the decrease in the sediment concentration were also beneficial to
the sediment prevention and elimination of the river channel.

Observation station

121°30′122°00′ (3) The implementation of middling narrowing project in the north branch of Yangtze estuary had basically nom³
m³

m³m³

Figure 4. Sediment concentration validation.
m³

Figure 1. Location of the project of North Branch Narrowing

m³121°00′

Flood tide peak sediment concentration(104 kg/s)
BeforeAfternarrowingnarrowing
Changeprojectproject (2) After the implementation of middling narrowing project in the north branch of Yangtze estuary, the river

m³

So

ming

A6

m³

A4

m³
m³

m³

Chom³
m³

Lianyungang

m³Santiaogang

B8
B7
B6

Tidal station

Figure 3. Flow velocity and direction validation.

B2

m³

Chongtou

Table 2. Section peak flow changes before and after the project.

Table 1. Section peak flow changes before and after the project.

more rationally and comprehensively.
32°00′

Figure 6. Sediment concentration distribution.

122°00′(b) after narrowing project

scientific basis for progressing the regulation project

121°30′121°30′Figure 5. Tidal current field in the spring tide flooding period.

numerically simulated and analyzed, aiming to provide

121°00′(b) after narrowing project

Shanghai

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Wu H, Zhu JR. Analysis of intruding saltwater transport mechanism in the north branch of Yangtze estuary[J]. Acta Oceanologia Sinica, 2007, 29(1):17-25.
Song ZK, Cheng HQ, Wu H et al. Numerical simulation analysis of the effects of reclamation in the north branch of Yangtze estuary on its hydrodynamics [J]. Yangtze River, 2012, 43(15):59-63.

effect on the tide level and sediment concentration distribution in the south branch and the entrance area.