Evolution Of Modern Yellow River Delta Coastal Environment

Get land use information from the remote sensing images of 1987, 1996, 2001 and 2006.In research period the area landward of high title line increase by 365km2.Land use changed in a fast speed(0.96%) and development degree is low. The area of land use types which is reformed by human increase and area under nature conditions decrease.Get tidal flat information from nine years remote images between 1976 and 2006. In the past 30 years, rapid erosion occurred in the area north to Gudong, and the coastline retreat 5.7km near Diaokou estuary and the largest retreat distance of this area is 12km.In the south part of Yellow River delta coastline retreat slowly. Near the Qingshuigou estuary coastline silting-up quickly and in the past 30 years coastline silting-up 15.1km.In the north-east part of the delta sea wall has been built to protect the coastline, and in the area high and low tidal line coincide, and tidal flat disappear.The changes of tidal flat is controlled by low and high tidal line, and the high tidal line is mainly controlled by human activities. In the north part of Yellow River delta high tidal line moved seaward because of reclamation, and the area of tidal flat decreased. In the area where coastline is protected by sea wall the tidal flat disappeared. The tidal flat near the new estuary area changed little and in the south part of the delta decreased because high tidal line moved seaward.Study the evolution trend of the under water slope with the water depth data between 1968 and 1999, in the north-west and south part of Yellow River delta under water slope deposit slowly. And near Diaokou estuary erosion occurred in the shallow water and sedimentation in deep water, and the transition zone is near the water depth of 12m. Near the Qingshuigou estuary deposit quickly in shallow water (less than 12~14m).Synthesizing evolvement character of offshore subaqueous terrain of different stages, we deduce the simulating formula of Yellow River Delta subaqueous slope evolution trend. Validate result shows that simulated results are accordant with evolvement trend of Yellow River Delta. The deduced result from the formula indicates that after 150 year since the estuary was abandoned, the shape of the under water delta disappear, and coast type changed from mealy sand to silty mud coast. The utmost scour depth scope in front of the sea wall calculated according to formula is 7-9m in Chengdao area, which is agreement with the prediction of maximum scour depth in front of sea wall.Study the effect of water and sediment regulation test on the coast evolvement during 2002.7-2004.7. The results indicated that siltation center whose maximum thickness excesses 10m, formed at the 2m water depth in the estuary. The deposition body mainly distributed in the mouth bar area, and water and sediment regulation test has little effect on the whole coast of Yellow River delta. And study the effect of large flow on the distributary channel. Results shows that flood is able enlarge the area of main channel and depth of the river. And then after the flood the main channel reinstate. And the study result also shows that we can shunt 150 m3/s flow to wetland area, it has no adverse effect on river channel degradation.