THE UTLLIZATION OF COASTAL MUDFLAT OF CHINA
Zhu Dakuin (Marine Geomorphology and Sedimentology Laboratory,Nanjing University)
Most of 2000 km of intertidal mudflat on the chinese coastline is devel- oped in the mesotidal Bohai sea and Yellow sea,along the great plain of north China and to the north of Hangzhou Bay. The coast slopes are very gentle with gradients of 1:1000 to 1:5000, thus,tidal currents play a major role in shapping the coast.The sediment consists of silt and clay to form extensive intertidal mudflats with the width normally 4 to 6 km,and the mudflats are up to 20km wide at the delta, The mudflats of Jiangsu are divided into four zones.(1)Supratidal zone (grass flats).It is marsh and the location is over the spring high tidal level. The sediment is very thin laimina mud-fine silt and marsh deposit.(2)Mud- flat.which is located between spring high tidal level and mean high tidal level,and consists of lamina and thin alternating laimina of silt and mud. (3)Mud-Sand fiats.They are located between mean high tidal level and middle tidal level,and consist of mudium laimina with cross-bedding.They are many.(4)Silt-Sand flats with the wave ripples surface acted by wave action. The mudflats are potential resources of farm land,especially for east part of China where over heavy population is.However,they are also good for developing salt fields,coastal lashing,other aquatic resources,and even there are many locations to be suitable for building harbor.For most part of inner two zone of mudflat,i.e.above mean HTL,and land-ward to the salt marsh can be reclaimated for developing agriculture,the lower two zones of mudflat are ideal ground for accumulating Shell fish such as Mere- trix,Cyolina Sinensis etc..It has greater economic value than reclamation. The mudflat coast represents a dynamic balance between wave erosion and deposition of unconsolidated sediment supplied principally by larger river,shch as Yellow River and Yangtze River.Thus,any engineering pro- ject related to the coast or river mouth there will cause a series of probl- ems.We do need more regional planning and marine legislation to strengthen the coast management.