GEO GRAPHICAL RESEARCH

Transcription

1 GEO GRAPHICAL RESEARCH Vol. 22, No. 4 J uly, 2003,,,, (, ) : ADCP ENDECO OBS 150km,, :, 2, ;,, ; : ; ; ; ; : P ; P33215 : (2003) ,,, [1 8 ],,, [1 13 ] ( ),,,,, () ( GPS ) 150km, (), (A ) (B ) ( ), ADCP OBS, ENDECO ( 2 ) (1),, : ; : : ( ) ; : ( ),,,

2 514 22, () 1 Fig11 The Changjiang estuary and sampling sites , L S230Q, A ( 2),,,, [14 ],, 10 %, mm,, [7,15 ],,, 0. 08mm (3. 64 ),, ( 2),, 12 %, ( 2),, 15 %,13 18 %, % [7 ] :

3 4 : Fig12 Grain distribution curves of bed sediments and suspended sediments (1),A 1. 92, B 2. 32, , (2), ( 1 3),,,, (k = ) (3) 4 A B, :,,, 2. 3 (A ) (B ),68, 90 %(A ) 84 %(B ) m/ s ( 2), m/ s,a 0. 7 m/ s, 7,B 0. 6m/ s, 6,,,, (A ) (B ),9,,,,A %,B 6. 0 %,, ( 2) 5 %,37, 1 Tab11 Particle size features of bed sediments D(mm) D(mm) A B ( ) (S 0 = 0. 8) (S 0 = 0. 8) ( ) ( ) (Sk = 0. 42) (Sk = 0. 54) ( K = 4. 24) ( K = 3. 32)

4 Tab12 Tidal current features at stations A and B ( ) ( ) A B Fig13 Grain size frequency curves of bed sediments 4 Fig14 Curves of probability accumulation of bed sediments grain size 2. 2, ( 3),, 5, 3,,1. 0m, m, 120m,15 75m, 70,,,, ( 5 - E), ( 5 - D) (m) 3 Tab13 Sandwaves features of Changjiang estuary ( ) ( ) (m) (m) (m) (m)

5 4 : 517,,,, [14 ],,,,,,, ( 5 - E) 5 (D,E ) Fig15 Profiles of the sandwave shape in Zhangjiagang Channel (D) and South Channel ( E),, 6 A B, 12, 4 5, 8 7,( ), 1. 5m/ s, A,, 6, Fig16 Current velocity curves at stations A and B,, B, A,,,,,,,,

6 518 22,( ),,,,,,(),,, 3 (),, 2,,,,,,,,,,(), : [ 1 ]..,1981, (1) : [ 2 ] Zhou Chengxi, et al. On sandwave in Yawosha channel of the Yangtze estuary. Proceedings of the Second International Symposium on River Sedimentation, Water Resources and Electric Power Press, [ 3 ] Hemminge M A,Cattrijsse A,Wielemaker A. Bedload and nearbed detritus transport in a tidal saltmarsh creek. Estuar2 ine, Coastal and Shelf Science, 1996, 42 (1) : [ 4 ]..,1992,19 (4) : [ 5 ],,..,1999,18 (4) : [ 6 ] Kenndy J F,Macro F. Waves generated sediment ripples. Lab. Rep., 1965,88 :55. [ 7 ] Li Jiufa, et al. The bedload movement in the Changjiang estuary. China Ocean Engineering,1993,7 (4) : [ 8 ],.., 1993,12 (2) :9 18. [ 9 ],.. : 1 :, [ 10 ] 1 ().,1984,3 (1) : [ 11 ],,..,1994,13 (1) : [ 12 ]..,1992, (4) : [ 13 ] ,40 (1) : [ 14 ],.. :, [ 15 ],.. : 1 :, [ 16 ] ,.

7 4 : 519 Field observations on bed sediments and sandwaves in dry season in Changjiang Estuary L I Jiu2fa, CHEN Xiao2hua, WAN Xin2ning, XU E Yuan2zhong, GU Jing2hua ( State Key Laboratory of Estuarine and Coastal Engineering, East China Normal University, Shanghai , China ) Abstract :A series of advanced instruments were applied to get the field data of bed sediments, riverbed shapes and relevant dynamic factors of t he 1502km2long reach f rom J iangyin to t he Hengsha Island in March The fine sand predominates t he bed sediment s in terms of granularity of bed sediment on the surface from Jiangyin to the Hengsha Island, the granularity becomes finer and finer from land to ocean. From the cumulated distribution of the bed sedi2 ments in the Changjiang estuary, we found that the rolling grains were absent in dry season and the saltation grains jumped twice. The first group was in majority and well2sorted because of the ebb tide, and the second group was in minority and bad2sorted because of the flood tide. The suspended sediment was also in minority and bad2sorted. There was st ronger flow and t he longer duration during the ebb tide in dry season and the grains could saltate fully and continu2 ously. The form of sandwave was related to the interaction of tidal current and sediment, the sandwaves grew well in the reach from Jiangyin to north of Zhangjiagang port, the lower reach of Nantong and south channel of the Changjiang estuary and so on in dry season, and which be2 came the major type of bed sediment transporting in estuary. In the Hengsha Island, the bed sediments were composed of fine sands and the sandwaves mostly dispersed to the upper reach, but the bed sediments were composed of clayey silt and sandwaves couldn t form in the follow2 ing north and south passages, which was accordant with the theory of dune formation on the bed. The direction of sandwave was normally vertical to t he flow direction, t he longit udinal form of sandwave might be symmetry or asymmetry, and the latter had the sharp slope in the lower reach and the slow slope in the upper reach. Near the tidal interface, the tidal current was greater during the ebb tide than that during the flood tide and the forms of sandwaves of the estuary were similar to those of rivers. But in the lower reach of the estuary, the quantities of transportation to the upper and lower reaches were both large, the sandwaves had symmetry forms and round crest s. In conclusion, t he sandwaves had more complicated influencing factors in the Changjiang estuary than those in the river, and which became the major form of bedload transportion in the Changjiang estuary. Key words : Changjiang est uary ;sediment ;bedload t ransport ;granularit y ;sandwave