| Since 2002,The Yellow River conservancy commission start the water-sediment modulation,has been conducted 14 times until 2012. The water-sediment modulation of the Yellow River is to regulate and control the flow and sediment transport relation of the lower reaches through reservoirs on thestreams and tributaries to create bailee between water and sediment so that sediment transport capacity of the dowristremi channels can be maximized, shrinking of channels be contained, and medium flood channel be restored and maintained-During the water-sediment modulation period the runoff and sediment into the sea accounted for third of the annual,the runoff and sediment gather into the sea will surely carry the significant impact on the Yellow River estuary and its adjacent sea. Therefore, recent research during the water-sediment regulation of estuary evolution and the development trend has great significance.Paper focuses on riverbed evolution of river estuary, foundation on the observed data of long series hydrological and sediment and riverbed evolution, adopts the method of power spectrum analysis and statistical analysis, analysis of the characteristics and influencing factors of riverbed evolution. Get the following main conclusions:(1) Lijin-Wang Jiazhuang cross-sectional variation mainly show section incised year by year, at the same time with a certain degree of stent, cross section shape to the benign development as a whole. At the same time, the differences in flood season and non-flood season changes in cross section is notable, the regularly flushing during flood season caused the cross-sectional last incised year by year, bigger influence on the depth. The flood of various natural and man-made force is relatively complex, cross-sectional shape is complex and changeable.Dongzhang-Yvwa depression period of cross-sectional evolution mainly show the section depth increases, the section width hasn’t significant change.So the cross-section mainly incised, broadening is not obvious. The flood river showed the characteristics of the swinging around, some years appear double channel section, but this characteristic in flood season scour then back to the original level, is not consistent.Q2-Q7 river cross-section overall perform incised and broadening, and more dramatic change. Q2,Q3,Q4 section 2,3, qing qing qing 4 is incised significant, cross sectional depth was bigger.Q6 and Q7 section width is mainly increase, this two sections is closer to the mouth, channel become more broad.(2) since the water-sediment regulation of each section of river estuary area as a whole are the change trend of fluctuations in growth. The biggest change occurred in the flood season in 2003, mainly due to the rare large autumn flood, flood happened with the autumn flood the water-sediment regulation of the Yellow River flood, achieved good effect of scour channel, far more than simply the effect of the water-sediment regulation engineering. Therefore, natural factors (precipitation, climate, etc.) in the impact of the channel at estuary section through a still occupy the important position, the water-sediment regulation engineering closely combined with the implementation of the natural factors work together to achieve a better effect. The change of sectional area can be divided into three sections,2002-2004, as the rapid growth stage; during 2004-2009 for small amplitude change growth stage; during 2009-2012 for the further growth of the growth of larger stage. Clear below Q2 river upstream area of growth is weak, mainly is the main source the influence of sedimentation.On the seasonal change of it, start from Lijin profile, the farther downstream area of the less seasonal change, to the Q7 section has been completely couldn’t distinguish the differences in flood season and flood season, the water-sediment regulation of water and sediment regulation of flood and flood season difference decreases, and by a certain degree of the influence of the deposition of the downstream river channel, but the scope is limited, the change of the estuary of river or human factor plays a decisive role.(3)During the initial of water-sediment regulation (2002-2004), Lijin-Wangjiazhuang section of river facies coefficient decrease quickly, after basic maintain fluctuations between 4-5, and volatility are getting smaller, river more and more stable form.Flood river and the flood season in coefficient of phase difference with the passage of time also is gradually decreases, and prove that the boundary between the flood and flood season difference gradually blurred.Dongzhang-Yvwa hollow cross section of the river and coefficient of overall decrease gradually, since 2002, the coefficient of a river cross section of the river and maintain within 6-9.5 level fluctuations, increase range than the front, reduced stability of cross section. Especially with the passage of time, after 2009, the stabilization of the channel, river facies coefficient of amplitude decreases, and the Dongzhang-Yvwa hollow cross section of the river and coefficient of variation also more and more small, coefficient of river facies in 8 floating up and down. Seasonal variation, the Dongzhang-Yvwa hollow section coefficient of river facies basic it is October than in May, the main channel in the flood season changing depth slice width narrow, it is significantly different with the front river. Further confirmed the narrowing of the difference between flood and flood season, and even the flood season of the river channel evolution degree of river channel changes has completely beyond the flood season.Q2-Q7 section of river facies complex coefficient change, fluctuation is bigger than upper reaches. Even after 2003 years, the river facies coefficient is between 6 and 20 fluctuations over a large area, and the annual variations is bigger also, overall, no significant increase or decrease trend.Seasonal variation, the river has obvious seasonal difference, a year two season river facies coefficient difference is bigger, and the differences between flood and flood season has almost no reflect.(4) the change of the profile, Lijin-Wangjiazhuang bottom elevation to reduce gradually, to the east of cross section and increased, after the Dongzhang-Yvwa hollow section presents the change of the ladder fell, qing 2 section after riverbed height increased again,Q3-Q7 section height is greater than Q2 section, completely in 2002-2012, Lijin to clear profile shape of the Q7 basic remains the same, roughly parallel to fluctuations "S".(5)Xiaolangdi reservoir as the most close to the downstream of Yellow River, to enter the downstream water sediment, is crucial. Since the implementation of the water-sediment regulation engineering 2002, regulation of the xiaolangdi reservoir is one of downstream river water and sediment process. Since the water-sediment regulation, the evolution of the estuary channel mainly presents the scour year by year, the characteristics of flood and flood season difference shrinking, these are the result of the water-sediment regulation water sand control. But according to the change of the section, you can see that the water-sediment regulation on the implementation of seven years before the effect is not very significant, but 2009 years later, the water-sediment regulation of long-term effects emerge gradually, the benign influence to the river more and more obvious and significant washout, estuarine river gradually tend to be dynamic balance, water and sediment regulation of the Yellow River is a long-term project, need for a long time for the water-sediment regulation can fundamentally change the water of the Yellow River sand not coordination problems.Natural process is also a very important factors of river estuary evolution. Lijin to Q7 section of 2003 autumn flood flood made significant positive response, cross section area and the coefficient of river facies in flood season have change dramatically in 2003, far more than simply the degree of change, the impact of the water-sediment regulation, visible natural role in the process of river channel evolution of river estuary still plays an important role, even more significant than the impact of the water-sediment regulation. So the process of the Yellow River is still to be combined with the natural role of governance, combined with the water-sediment regulation, maximum full play its regulatory governance role.Marine force also has certain influence on the river channel, mainly displays in the clear section below the roots of alluvial role in Lijin to Q2 river, Q3 basic is not affected by the influence of sea power. Population change of Yellow River basin, water diversion project, water conservation measures such as process is also affect the changes in water and sediment and river channel evolution of the very important factors. And other factors that can cause water loss, such as evaporation, seepage quantity river, Yellow River water, etc., these factors under the Lijin river comprehensive loss caused by the smaller. |
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