LAND-FORMING HISTORY OF THE HUANGHE RIVER DELTA AND COASTAL PLAIN OF NORTH JIANGSU
Zhang Ren-shun (Nanjing University, Nanjing)
In historical period, the Huang He River flowed through North Jiangsu into the Huanghai sea for nearly 700 years. The abundant load that it carried formed a large delta, a coastal plain and offshore banks. It is due to the shifting of the river estuary that the coastal zone in Jiangsu underwent two great changes in hydrodynamical and sedimentological condi-tions, but the results they brought about are contrary to each other! Through careful analysis of historical literatures and field investigations, this paper at-tempts to discuss the land-forming process of the Huang He Delta, the coastal plain of North Jiangsu and analyse the great effect of the shifting of the river estuary brought on the coas-tal development. The chief conclusions obtained are as follows: 1. Before 1128, the coast of North Jiangsu was a barrier island coast. Since the Huang He River captured the lower reach of the Huai He River and flowed into the Huanghai Sea, the coast has gradually taken the form of a mud plain coast. 2. Hereafter, the land-forming history of the coastal zone is divided into two stages. Before the middle Ming Dynasty, the extension of the estuary was 54 m/a and the rate of the growth of the delta was 3.2 km2/a on the average. After the middle Ming Dynasty, the rate of progradation of the coast was increased to 223 m/a and 15.5 km2/a. 3. The main land-forming process of the coastal plain consists of the unification with the offshore banks. The rates of increase of coastal land are irregular. They are 2.7 km2/a before the middle Ming Dynasty and 10 knr/a after the middle Ming Dynasty. 4. Because of the shifting of the outlet of the Huang He River into the Bohai Sea in 1855, the coastal zone of North Jiangsu lost the source of abundant sediment but it had to adjust to this great change. The coastal zone of Jiangsu subjected to (1) serious erosion and most of the eroded material transported southward; (2) The pattern of the offshore banks has been gradually transformed into radiated shape; (3) The length of receding coastline is gradually increased and the rate of progradation of the coast in central jiangsu decreased.