关键词: 海岸侵蚀, 潮汐水道, 人类活动, 江苏

Abstract:

The coast of Jiangsu is famous for its dynamic singularity of both serious eroded coast reach and rapid progradingone. The erosional coast of Jiangsu is 301.7km long or 31.6% of the province total shoreline. Of them muddy coast is 271.6km and sandy coast, 30.1km, which is the only segment of sandy coast in Jiangsu. This singularity is relevant to the following three features. The first one is the effect by great changes of the two big river mouths. The lower reaches of the Huanghe River began to enter the Yellow Sea by north of Jiangsu in 1128 after capturing the Huaihe River and was back to the Bohai Sea by Shandong Province in 1855. This evolution of the Huanghe River, which famous for carrying plenty of sediments, caused great hydrodynamic change, especially the sedimentation conditions of the Jiangsu coast. The second one is the long muddy coast.During the 700 years that the Huanghe River entered the Yellow Sea by Jiangsu, the coast was transformed from sandy coast to muddy, and 92% of the shoreline of Jiangsu is muddy coast now. The third one is the diversity of the openness of the several coast reaches. With the substantial change of the large-scale submarine sand ridge fields on the inner continental shelf, the screening state of the coast reaches changes accordingly. There are four segments of the erosional coast reaches in Jiangsu. The first one is the abandoned Huanghe River Delta coast. The delta shoreline and the subaquatic delta have been heavily eroded because of the losing of sediments supply. Meantime, the coast reach of the abandoned river mouth retreated rapidly and has not been controled until the 1970s when the seawall and the bank protection were built. But this promotes the vertical erosion on the intertidal flat.The average rate of vertical erosion from 1980 to 1992 is 13.5 cm/a. The isobath of 15 m is only 4.65 km away from the bank, and the isobath of 10 m moved 0.37 km every year toward the bank from 1937 to 1994. The second isLusi coast, the southern part of the coast of Jiangsu. The erosion of this segment is mainly because of large-scale tidal channel movement toward the bank and development of winding. The shoreline retreated more than 1 km from 1916 to 1969. The super tidal flat in front of the seawall was wholly eroded, and the rate of vertical erosion on the intertidal flat is 3.6 cm/a. The third segment is the Jianggang coast. Some tidal creeks on the tidal flat moving toward the bank caused heavy erosion, and some erosional mud cliffs are as high as 5 m. The cliffs can retreat 20-30 m within one spring tide cycle. The fourth is the sandy coast in the northern part of Jiangsu coast. Some dams were built on some rivers flowing into the sea and break off the sediment source supplying the coast. Meanwhile, digging of coastal sands helped the erosion.

Key words: coastal erosion, tidal channel, anthropogenic activity, Jiangsu coast