黄河三角洲海岸岸线和潮水沟体系发育及其分维研究──黄河三角洲潮滩海岸时空谱系研究Ⅲ

Researgh on the Development of the Huanghe River Delta Coastline and the Tidal Creek System as well as Fractional Dimension ──Research on the Space-Time Lineage of the Tidal Bank Coast of the Huanghe River Delta Ⅲ

千年来,黄河三角洲地区尾闾入海河道在大口河～淄脉沟之间频繁摆动,各时期行水河口形成的河口滩均有宽大的潮间地带,但从地貌-沉积发生学上并不具备潮滩的性质;当行水河道摆走后,原河口滩摆脱了河口径流水沙的直接作用而被"废弃"?在海洋动力的作用下向潮成海滩的方向发育,"废弃"的时间越长,潮滩发育得越成熟?黄河三角洲洲边大多数海岸,属于处在不同发育阶段的潮滩型海岸;三角洲的东北角海岸地处区域 M2分潮无潮点附近,被"废弃"的河口滩逐渐被盛行强风浪作用剥平形成浪蚀型海滩?因此,黄河三角洲洲边并存三元谱系海滩,即河口滩?潮成海滩(潮滩)和浪蚀海滩,它们各具有自身的特点?本文将三角洲岸线和潮水沟体系分维 D 作为指标,对三角洲海岸发育时空谱系作进一步探讨?计算分析表明,区域内岸线分维与潮滩发育的时间成正相关,特大高潮岸线尤为明显,如古代黄河三角洲岸段岸线的分维值 D 为 1.1356～1.1625,而近代黄河三角洲平均变化在 1.091～1.118 范围内?平均高潮岸线分维值 D 也有相应的一定程度的变化;对三角洲洲边不同发育年代( 100～103 a )的 23 个潮水沟体系进行 m 级分辩率分维值 D 测计结果显示,在行水河口滩区岸和发育时间短?潮差小的区段( 如浪蚀海滩 )沟系( 含潮水沟和径流水道 )的分维值 D 较小,?

Over a millennium, the terminal river course emptying into the sea in the Huanghe River delta area was frequently oscillating between Dakouhe and Zimaigou. The estuarine banks resulted from the flowing-water estuaries in various periods all have broad tidal zones, but, in the genetic geomorphology and sedimentology, they do not possess the character of a tidal bank. When the flowing-water water course swings away, the original estuarine bank having shaken off the direct action of the estuarine runoff water and sand is 'abandoned', and, under the action of ocean dynamics, develops towards the tidal bank, and the longer the time of'abandonment' is ,the more matured the tidal bank develops. Most of the coasts at the edge of the Huanghe River delta belong to the coasts of tidal bank type in different stages of development; The coast around the northeastern corner of the Delta is situated near the amphidromic point of the M2 constituent and the 'abandoned'estuarine bank is gradually denuded under the action of the prevailing strong wind and wave to evolve into the wave-cut beach. Therefore, at the edge of the Huanghe River delta there coexist the ternary lineage beaches, i.e., estuarine beach, tidal beach and wave-cut beach, each of which has its own characteristics. This paper makes a further discussion on the space-time lineage of the delta coast development with the fractional dimension D of the delta coastline and tidal creek system as an index. Results of calculation and analysis indicate that within the region the coastline fractional dimension is positively correlated with the time of tidal bank development, which is especially obvious in the case of the exceptionally high tide coastline. For example, in the ancient Huanghe River delta coastal section, the fractional dimension value D of the coastline is 1.135 6～1.162 5 while in the modern Huanghe River delta it varies between 1.091 and 1.118 on the average. The fractional dimension value D of the mean high tide shoreline also varies to a certain extent correspondingly; Results of the calculation of the m-level resolution ratio fractional dimension value D of the 23 tidal creeks around the Delta in drfferent years of development ( 100～103a) show that the fractional dimension values D at the coasts of the flowing-water estuarine banks and the creek systems ( including tidal creeks and runoff waterways ) of the sections ( such as wave-cut beach ) with shorter time of development and small tidal range are smaller, varying between 1.385 4 and 1.491 1 on the average; The fractional dimension value D at the sections where the evolution time from the abandoned estuarine bank to the tidal bank is longer and the tidal creek system at the section between the inter-mouth bay and the mud bay is greater, varying between 1.624 6 and 1.843 5. This is the tidal-bank type coast, on which are developed densed, multi-level and branching tidal creeks of different sizes. The fractional dimension values of the groove system on the various sections of the coastline of the Huanghe River delta and the beach bodies may be taken as a major locating index for the space-time lineage resulted in the course of time dimensions when the shore beach is subjected to the combined effect of the river-tide-wave and the bottom topographical boundary conditions.