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Poster Session Q
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Remote Sensing study for environmental and engineering geology in Lianyungang
Cai Zejian, Yan Gang
Remote Sensing Station, Geology of Jiangsu, Nanjing, China
Abstract
Lianyungang lies on the bank of the Yellow Sea. It is one of the most important harbor cities, which are open to outsides in the East China. With the development of economic construction in the region. the environmental and engineering problems become more urgent and serious ones. Based on the MSS and TM image data provided by Landsat 2.5 of USA and its combined analysis with aerial photos and geophysical and drilling data, it is stated that not one coastal current flowing from North to South commonly known before but two coastal currents flowing North to South alternatively exit. It is possible that the harbor is silted up after it is sealed off in one side. It is advocated that the dam across the sea must be built in ' open ' state to allow the currents to flow through. The disadvantage engineering geological factors such as active faults, distribution of soft mud layers, landslides
Image feature of coastal currents and its movement in Lianyungang.
Lianyungang lies in the middle of the bank of the Yellow Sea. It has coastal line of about 120 km. Many rivers enter into the Yellow Sea at the plot, where coastal geomorphology develop well. There are three types of coasts, ie: depositive, erosive and steady cost (Fig.1). Based on analysis of the shifting of main channels of sea-entering rivers and the dynamic features of coastal geomorphology, it is stated that two coastal currents exist, flowing from N to S alternatively, By comparative analysis of photos of three periods ( 1954, 1964, 1983), it is discovered that the 'claw' sand mouth in Longwanhe river mouth in Haizhou Bay stretched out about 600 m from N to S in 30 years, at the average rate of abut 20 m per year. The stretching as more clear at 'claw-head' (Fig.2). With no exception, the claw sand mouth in sea-entering river mounts is Haizhou Bay stretch out from North to South at different rate. It depicts that materials brought by inner rivers, effected by a coastal current from N To S at river mounts, is forced to deposits in the sought of rivers in Hai hou Bay.
Opposed to the drifting tendency of sand mounthes in Haizhou Bay, main channel of Liezhihe river mouth, originally flowing towards SN< deviated 30!c westward in 30 years from 1954 to 1983. Deviation rate was about 10 per year. Generally main channels in Liezhihe-Guanhe deviate from E to W. Shell sand dams develop will in wide region in the east of Lianyungang. All of waving axes of the well developed sand dams arrange in oblique from NW to ES (Fig 3). All of these show that the formation of the shell sand dams are restrained strictly by the coastal current flowing form S to N.
The satellite images show in a larger range that there exist two coastal currents flowing form N To S alternatively (Photo 1 Landsat2 MSS4). The coastal current form the South, carrying the large amount of mud and sand from abandoned Huanghe river mouth, flows northward. Combined with the coastal current from North haizhou Bay at the east of the harbor, it stretches out and diverse towards sea.
The amount of mud and sand brought by the coastal current from the South and its moving rate seems to be the one brought by the current from the North and its moving rate.
From the intepretation results of remote sensing data stated above, it can be drawn definitely that not only the coasttal current flowing from S to N, but also the one from N to S exist and act on in the near bank.
The discovery will bring about great effect on back-forth, deposition-erosion of the coastal line and series of engineering construction along sea bank. It is significant that researches of directions, patterns and effects of coastal currents are carried out.
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