Influence Of Flow/Sediment Regulation In Xiaolangdi On Incoming Flow/Sediment Condition And Coastline Evolution Of The Yellow River Estuary

Coastal zone is the front region of human survival and socio-economic development, whooccupies an important position in the global ecological environment changes. The coastalspatio-temporal evolution analysis is the most basic subject to study the response of coastalzone to human activities. To a certain extent, the coastline changes often bring serious harm tothe ecological environment of the coastal areas and seriously impede the economicdevelopment. The Yellow River Tail migrates frequently, which is the fastest-growing changeregion in the world, whose ecological environment is very fragile. Therefore, it has a practicaland far-reaching significance for sustainable development of socio-economic in the YellowRiver estuary and provide some practical reference value for the overall planning of thecoastal zone to strengthen the coastline research.The paper takes the coastal zone of Yellow River estuary as the study area, using3S as themain technical means, based on the hydrological data of Lijin station and14Landsat TMsatellite images from1976to2010, adopting the methods of the combination of statistical dataanalysis and Practice, qualitative analysis and quantitative analysis, starting from the variationrules of flow/sediment in the Yellow River Estuary before and after the Xiaolangdi operation,making dynamic process of coastline as the main line, scientifically studying relationshipbetween flow/sediment conditions and coastline evolution of the Yellow River and revealingthe effect mechanism of flow/sediment regulation on coastline, which to set up scientificregulation measures. The results show that:The flow/sediment abundance of the Yellow River shows a decreasing trend year by yearand High and Low flow/sediment alternating change characteristics, mainly concentrated inthe flood season (July to October), the violent inter-annual fluctuations, a single peak formchange during the year, frequent occurrence of flow-break in90s; the stage changes of coastline in the Yellow River Estuary is significant, the siltation stronger than erosion, mainlyadvancing to the sea as a whole, the coastline length increasing1.1km, sand spit extendinginto the sea0.34km, land-forming6.4km2in an average annual, coastline shape tending tosimplistic.The flow/sediment regulation role of Xiaolangdi advance the Yellow River flood seasonstart period to June, the end period extended to11months, the amount of flow/sedimentdistributing more evenly during the year, but27.4%,72.1%less than the condition undernatural conditions; it optimizes the flow/sediment allocation, Making the ratio offlow/sediment and incoming sediment coefficient stabilize at0.01t/m3、0.01kg·s/m6; it keeps acertain flow and flood peak(3000~4000m3/s) all the year-round, which restrain effectivelythe occurrence of flow-break.The coastline change cycle lags behind the flow/sediment condition of the Yellow River forabout a year, and they show a significant positive correlation. Period (1977-1995) inQingshuigou Channel, higher flow/sediment levels make coastline rapid situate and expand,the coastline length increasing1.63km, sand spit extending0.91km, land-forming14km2in anaverage annual, coastline shape tending to complex; the initial Period (1996-2003) in Northbay Channel, a very small amount of flow/sediment and deteriorating flow/sedimentconfiguration make the coastline overall appear retreating situation, a total of3.6km spiterosion,69.68km2of land area reduction,12.57km of coastline length reduction from1999to2003; the early Period(2003-2006) of flow/sediment regulation, the coastline siltationintensity was significantly superior to the natural conditions, the coastline length increasing4.3km, sand spit extending0.9km, land-forming28km2in an average annual, coastline shapetending to simplistic. Wherein, the coastline length increasing rate is twice that of the earlystage of channel diversion of the Yellow River to Qingshuigou route, spit extension length forevery million tons of sediment is2.9times, land-forming rate is1.34times; recent years(2006-2010), although flow/sediment regulation restrain the flow-break, lower the amount offlow/sediment make the coastline suffer erosion, the coastline length decreasing2.9km, sandspit erosion1.1km, land-forming retreating13.75km2in an average annual. Sand spitextending rate is subject to the ratio change of flow/sediment and they show an obviousquadratic equation with one unknown relationship: V=-13539r2+576.85r-5.2906(where V is sand spit change rate, r is ratio change of flow/sediment in the Lijin station); speed ofland-forming and incoming sediment coefficient show a significant negative correlation.Thus, reasonable flow/sediment regulation can allow the coastline develops toward thedeposition direction and unreasonable flow/sediment regulation can make the coastline facethe danger of retreating. It is a critical condition for the coastline develops toward the sounddirection to control the ratio of flow/sediment0.02t/m3and incoming sedimentcoefficient0.01-0.015(kg·s)/m6in Lijin station (which is about20billion of flow,3-4milliontons of sediment and6.34-9.52kg/m3of sediment load sediment concentration) byflow/sediment regulation. According to the forecast analysis, the coastline near North sandspit will further extend into the sea and southern sand spit will continue retreating from2011to2020. The whole coastline tends to be more straight and smooth and gradual translates tothe dynamic equilibrium.