长江分汊河口水力几何形态
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摘要
为了揭示潮汐河口中居显著地位分汊河口的演变机理,减轻长江口深水航道淤积.基于积分形式二维连续方程、二维阻力公式、无因次宽深比关系与时变水流挟沙能力公式,建立分汊河口水力几何形态理论关系,且表明汊道与单一河道平均水深之比为分流比的2/7次方.据此计算获得了长江口拦门沙顶部最大平衡水深为6.91m,与长期实测的自然水深相一致,显示了水力几何形态关系的合理性.引入主槽流量比例概念,进一步修正水力几何形态关系,使之适合于丁坝作用河段.据此计算得到在一、二和三期治理工程后北槽的最大平衡水深分别为8.40、8.91和9.92m,为制定长江口治理方略提供了理论依据.
For the purpose of revealing the mechanism of morphological evolution in the branching estuary which is a prominent type of tidal estuaries and reducing siltation in the Yangtze Estuary deepwater channel,a new relation for the hydraulic geometry of branching estuary was developed by solving the 2D continuity equation in integral form,2Dresistance equation,dimensionless width-depth ratio relation and time-dependent sediment transport capacity formula.The ratio of mean depths of a distributary channel and the main stream is a power function of its bifurcation ratio with an exponent of 2/7.The maximum equilibrium depth at the top of mouth bar in the Yangtze Estuary was calculated as 6.91 mby the proposed hydraulic geometry relation.The result agrees well with the depth acquired from long-term measurement data,which proves the reasonability of the new relation.Furthermore,the hydraulic geometry relation was modified to consider the effect of the groins built in the North Passage by introducing the concept of main channel discharge proportion.The maximum equilibrium depth of the North Passage after the three stages of deepwater channel regulation project was hereby calculated as 8.40,8.91 and 9.92 m.This lays a theoretical foundation for developing strategies to regulate the Yangtze estuary.
For the purpose of revealing the mechanism of morphological evolution in the branching estuary which is a prominent type of tidal estuaries and reducing siltation in the Yangtze Estuary deepwater channel,a new relation for the hydraulic geometry of branching estuary was developed by solving the 2D continuity equation in integral form,2Dresistance equation,dimensionless width-depth ratio relation and time-dependent sediment transport capacity formula.The ratio of mean depths of a distributary channel and the main stream is a power function of its bifurcation ratio with an exponent of 2/7.The maximum equilibrium depth at the top of mouth bar in the Yangtze Estuary was calculated as 6.91 mby the proposed hydraulic geometry relation.The result agrees well with the depth acquired from long-term measurement data,which proves the reasonability of the new relation.Furthermore,the hydraulic geometry relation was modified to consider the effect of the groins built in the North Passage by introducing the concept of main channel discharge proportion.The maximum equilibrium depth of the North Passage after the three stages of deepwater channel regulation project was hereby calculated as 8.40,8.91 and 9.92 m.This lays a theoretical foundation for developing strategies to regulate the Yangtze estuary.
引文
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[3]刘杰.长江口深水航道河床演变与航道回淤研究[D].上海:华东师范大学,2010.LIU Jie.Study on morphological evolution and si1tation in deep waterway due to channel re-construction in the North Passage,Yangtze estuary[D].Shanghai:East China Normal University,2010.
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[8]孙志林,夏珊珊,朱晓,等.河口时变水流挟沙能力公式[J].清华大学学报:自然科学版,2010,50(3):383-386.SUN Zhi-lin,XIA Shan-shan,ZHU Xiao,et al.Formula of time-dependent sediment transport capacity in estuaries[J].Journal of Tsinghua University:Science and Technology,2010,50(03):383-386.
[9]谢鉴衡.河床演变及整治[M].2版.北京:中国水利水电出版社,1996:26-27.
[2]金镠,虞志英,何青.深水航道的河势控制和航道回淤问题[J].中国港湾建设,2012(01):1-8.JIN Liu,YU Zhi-ying,HE Qing.Study on river regime control and siltiation in deepwater channel.[J].China Harbor Engineering,2012(01):1-8.
[3]刘杰.长江口深水航道河床演变与航道回淤研究[D].上海:华东师范大学,2010.LIU Jie.Study on morphological evolution and si1tation in deep waterway due to channel re-construction in the North Passage,Yangtze estuary[D].Shanghai:East China Normal University,2010.
[4]严以新,高进,宋志尧,等.长江口九段沙分流计算模式及工程应用[J].水利学报,2001,04:79-84.YAN Yi-xin,GAO Jin,SONG Zhi-yao,et al.Calculation method for stream passing around the Jiuduan sandbank in the river mouth of Yangtze River.[J].Journal of Hydraulic Engineering,2001(04):79-84.
[5]窦国仁.平原冲积河流及潮汐河口的河床形态[J].水利学报,1964(02):1-13.DOU Guo-ren.Riverbed form of plain alluvial river and tidal estuary[J].Journal of Hydraulic Engineering,1964(02):1-13.
[6]SASSI M G,HOITINK A J F,de BRYE B,et al.Downstream hydraulic geometry of a tidally influenced river delta[J].Journal of Geophysical Research:Earth Surface,2012,117(F4).
[7]NIELD J M,WALKER D J,LAMBERT M F.Two-dimensional equilibrium morphological modelling of a tidal inlet:an entropy based approach[J].Ocean Dynamics,2005,55:549-558.
[8]孙志林,夏珊珊,朱晓,等.河口时变水流挟沙能力公式[J].清华大学学报:自然科学版,2010,50(3):383-386.SUN Zhi-lin,XIA Shan-shan,ZHU Xiao,et al.Formula of time-dependent sediment transport capacity in estuaries[J].Journal of Tsinghua University:Science and Technology,2010,50(03):383-386.
[9]谢鉴衡.河床演变及整治[M].2版.北京:中国水利水电出版社,1996:26-27.