THE ROUGH BALANCE OF PROGRADATION AND EROSION OF THE YELLOW RIVER DELTA AND ITS GEOLOGICAL MEANING

Coastal line erosion and delta area decrease are becoming a hotspot for governments and scientists in the world.The trend and velocity of formed land restrict the economic development and ecological environment evolvement in delta area.According to coastal line changes during the high tidal periods of 1976,1986,1992,1996,1997 and 1998,the trend of progradation and erosion of the Yellow River delta was studied.The results show that the coastal line progradation and erosion are proceeding simultaneously,and generally the formed land area in the delta is decreasing.The results of water discharge analysis and sediment load from 1950 to 1998 and their relation to the formed land area show that when sediment load is 2 45×10 8 t,the delta of the Yellow River will have rough balance of progradation and erosion.