The Study Of The Erosion Of Diaokou Course Coast In Yellow River Delta

To study the erosion of the north of the modern Yellow River delta after Diaokou course was abandoned, we've gathered water measure data and study its law of erosion and fill. Then we discuss the mechanism of its erosion in two sides. One side we discuss it from the hydrodynamics based on wave observation data during a storm, mainly including wave, tide and storm rip current, etc. Another side we discuss it from the relative rise of sea level and forecast the erosion rate by Bruun's rule. Finally we discuss fence measure, simply describing constructed fence architecture, analyze existent problems and put forward some advices.Through studying the change of coastline and water delta, we see that deposition occurs around new river mouth and erosion occurs near Diaokou course after Diaokou course was abandoned. Then we traverse the landform change of 8 northern sections. The change of 1-3 section is very small, while the top of 5-8 section was eroded soon before 1990, then came into slow change stage. We also see that there is a position of which the upside is eroded and the underside is filled, whose change is small, and whose grade is max when Diaokou course was abandoned in 1976. The position' water depth in every section is different probably for every section lying in different part of Diaokou course. The position' water depth of the sections around main branch is 11 -13m, and The position' water depth of the sections by secondary branch is 7-9m. Studying the change of isobaths in the level and vertical direction and the change of grade of 5 and 8 section, we see that the isobaths change around some isobath whose change is small. Before 1990 the above isobaths backed off and eroded soon, and the down isobaths went ahead and silted, so the grade of the landform gradually become small; after 1990, the change of the isobaths is small, and the grade of all sections is about l%o but 8 section' grade is relatively bigger for the bigger wave energy. By the former study, we think that there is relatively steady section in the northern part of the Yellow River delta.Dealing with wave observation data, we see that the waves of observation spot are mainly Airy waves and Stokes waves. During storm, the waves are mainly Stokes waves which distort asymmetrically, while the waves distort badly in the center of storm whose level rises, and there are waves beyond limited wave steepness which may affect the transport of sediment especially badly. We compute the sediment transport intensity between wave distortion and crash by the formula of Einsteinian's sediment-transport rate, and the sediment transport intensity is positive and largen shoreward implying transporting sediment shoreward. Spreading shoreward, the waves will break up to form surf zone where for the action of turbulence the sediment is suspended and transported by tidal current and remaining current, so the upside of underwater delta is eroded after Diaokou was abandoned. During storm, wave set up will flood a great deal of land, and large wave height and wave length largen the sediment transport intensity, then the storm may lead togread erosion of coast and underwater landform.We discuss sea level rise's effect on erosion. The factors which lead to sea level rise mainly include construction and equilibrium sinking, concrection and compact sinking and absolute sea level rise. We compute erosion rate of coast for sea level rise by Bruun rule. When Yellow River is abandoned, coast erosion rate reach to 156m/a.We list familiar fence measure, mainly including sea wall, spur and off-shore bank etc. There are 3 sea walls in modern Yellow River delta: Chengdao sea-wall and Gudong sea wall in the north of the Yellow River mouth, newly constructed sea wall in the south of the Yellow River mouth. Through studying, we see that the recovery of northern sea wall is stronger than southern sea wall whose structures are different. Jetties are constructed by docks, of which lower reaches are sea-route and fleet where boats anchor. Although these project measures are cons...