Study On The Delimitation Between The Modern Yellow River Delta And The Sea

The Yellow River is located in north of Shandong province, no south of BoHai sea. It connects Shandong peninsula to Beijing and Tianjin. It is one of the three deltas of China with great potential. However, Yellow River goes slower in development compare with other deltas include Changjiang and Zhujang delta. There are great complex interest conflicts in estuary. The influence is enormous and it needs a uniform and holistic management and should making overall plans and take all factors into consideration. The key to solve this question is to set down an reasonable delimitation between land and sea.This paper studies the delimitation about the estuary and the expand in the modern Yellow River delta with culmination Yuwa from Tiaohe bay to Songchunrong estuary about 2200km2 by use other estuary for reference and bases on productions and questions anciently. This paper analyses four natural factors for delimitation mostly-landform, physiognomy, matter on bottom , biology and coast stability.The study indicates that: (1) The broad area reach to sea is new wetland and it is typical interdital zone landform. The fall of gradient of subsea topographic which is the extend of land topographic is slow. The deepness turns bigger and the isobaths and coastline have parallel direction. There is obvious gradient only under the lowtide-line. So, the factors of landform and deepness are not the primary element in delimitation research which can be used for background gist. (2) There is obvious physiognomy change of turning of new wetland and sea in area reach to sea and interdital zone in the interspace. In the coast beside the area reach to sea, there is obvious change of physiognomy from bank to man-made physiognomy such as shrimp pond. It is very important delimitation that the use of physiognomy change connect with other geology characteristics. (3) Two types of the sediment area were formed: intertidal zone deposit area and shallow sea deposit area. The matter composing of seabedsurface layer turns fine from coast to sea. The type of matter on bottom parallels the coast mostly and turns seasonal. So it can be used only for background gist in delimitation. (4) The investigation area is affluent in biology resource and zoology value. However, most of the economy biology species are lacking in quantity and can not used for business. The seawater breed is in charge of marine department. So it is of little influence in delimitation. (5) The coast along the modern Yellow River Delta can be divided into two parts: eroded coast from Tiaohekou to Sihaozhuang and progradational coast from Sihaozhuang to Songchunrong channel mouth.This paper analyses some criterions of delimitation. The delimitation between land and ocean: average spring tide high tide line, average low tide line, boundary line between the delta plain and undersea delta front, nature reserve boundary; the delimitation between river and ocean: sand bar criterion and mouth bar criterion. It considered nature reserve boundary and mouth bar the best land-sea boundary line.