现代黄河口沉积动力过程与地形演化

发布时间：2018-04-03 05:07

本文选题：黄河口　切入点：沉积动力　出处：《中国海洋大学》2014年博士论文

【摘要】：本文基于黄河三角洲及莱州湾多年历史资料，以水环境动力学模型（MIKE3）为基础，建立起一系列沉积动力模型。通过实测资料对模型的率定与验证，模拟了1976年黄河改道清水沟流路以来，河口的潮流、切变锋及波浪各时期的特征并分析讨论了其演变过程。通过对模拟结果和实测地形冲淤变化分析，综合研究了黄河口潮流切变锋在一个完整黄河流路期内的演变规律和成因，潮流切变锋在大风及地形共同作用下的变化规律及成因，黄河口动力变化下的工程波浪安全隐患等问题，发现了落潮切变锋强度始终强于涨潮的规律，阐述了黄河口沉积动力演变与地形演变的相互作用关系和模式，揭示了以风致切变锋变化为基础的河口冬季泥沙扩散新动力机制，提出了黄河口特有的海洋工程环境动态参数设计理念及预警防护建议。研究表明，黄河口潮流切变锋和潮流场于1976~1996年黄河清水沟流路行河的20年间，在空间、时间和强度上均具有显著的演化规律。其根本原因是水深地形的变化。进一步，切变锋演变反应了潮流场的演变，后者与河口地形的演化存在双重相互作用关系，表现为河口增长会促进潮流增强并限制河口增长，，最终在一定径流输沙范围内稳定；河口蚀退会使潮流减弱，使侵蚀由强变弱，侵蚀速率由快变慢。大风过程对黄河口潮流切变锋具有明显的影响。6级大风即可使切变锋产生变化，风力越大，变化越明显。大风通过在近岸浅水区生成风生流使切变锋发生变化，平行锋面的大风增加其强度，垂直锋面的大风减弱其强度；偏北向大风加剧涨、落潮切变锋强度“落强涨弱”形势，偏南向大风则相反。河口地形是使各风向大风对切变锋产生不同影响的决定条件和必要条件。潮流切变锋在冬季偏北向大风的作用下，存在着切变锋强度减弱、口门锋面消失以及涨潮切变锋基本消失三种有利于河口泥沙扩散的变化，使大量波致再悬浮泥沙在多种情况下突破原有锋面阻挡，向莱州湾中部或湾口扩散。风致切变锋变化是泥沙“冬输”动力机制中不可忽略的重要因素之一。黄河口潮汐过程由于存在不对称性，落潮流流速、历时均大于涨潮流，使得落潮切变锋在长度、历时和剪切强度等方面均强于涨潮切变锋，且在常见偏北向大风影响下，二者差异被放大，甚至在较少情况下涨潮切变锋接近消失。落潮切变锋强度大于涨潮切变锋的这一规律在潮汐不对称性和季风影响下长期存在。黄河口重现期大浪受地形变化影响显著。清水沟流路老河口海域平均水深每增加1m，50年一遇NE向有效波高增加约0.4m，1996~2012年平均增长约1.1m，增长率约为0.07m/a。根据波高变化可将黄河口地区分为三部分：新河口安全区，新老河口间隐患区，老河口危险区。未来10年，隐患区和危险区均面临着由岸线继续蚀退所带来的陆地环境浅海化、浅海波浪增强等安全隐患。根据动力与地形相互作用的理论研究结果，对黄河口河道备选流路，近海工程海洋环境快速变化引发的安全性隐患等实际问题提出了相关建议。着重阐述了推广海洋工程环境动态参数设计理念及预警防护建议的迫切性和必要性，并对该理念的施行提出了多套参数设计、定期调查与预警防护补救措施等建议。最终，通过近3年的研究工作，本文具有如下创新点：（1）揭示了黄河口潮流切变锋在一个完整黄河流路期内的演化规律及其成因，并阐述了河口地形演化与潮流场演化的相互作用关系及过程。（2）发现了黄河口潮流切变锋对大风过程的响应规律及其机制，并从该角度揭示了黄河口冬季泥沙扩散新的动力机制，完善了河口泥沙“冬输”过程的动力机制研究。（3）明确了黄河口涨、落潮切变锋在常规与极端气象条件下的变化过程，发现了落潮切变锋强度始终强于涨潮这一规律及其成因。（4）研究了黄河口重现期大浪对地形演化的响应，提出黄河口海洋工程环境动态参数设计理念及预警防护建议。
[Abstract]:Based on the historical data of the Yellow River Delta and Laizhou Bay , this paper establishes a series of sedimentary power models based on the water environment dynamics model .

The study shows that the tidal current shear front and tidal current field of the Yellow River have remarkable evolution law in space , time and intensity during the 20 years from 1976 to 1996 . The root cause is the change of water depth topography . Further , the evolution of shear front reflects the evolution of tidal current field .
The erosion of the estuary will weaken the tidal current , cause the erosion to change from strong to weak , and the rate of attack will change from fast to slow .

The strong wind can make the shear front change , the bigger the wind is , the more obvious the change is . The strong wind in the shallow water area changes the shear center , the strong wind of the parallel frontal surface increases its strength , and the strong wind of the vertical front face attenuates its strength ;
The change of wind shear front in the middle or the Gulf of Laizhou Bay is one of the important factors that can not be neglected in the dynamic mechanism of sediment " winter transmission " .

The tide process of the Yellow River Estuary is stronger than that of the rising tide due to the asymmetry , the flow velocity and the duration of the ebb current , so that the ebb and shear center is stronger than the tide shear front in terms of length , duration and shear strength .

The average water depth in the Laohekou sea area of clear water channel is increased by 1 m and the average growth rate is about 1.1m from 1996 to 2012 . The growth rate is about 0.07 m / a . According to the wave height variation , the Yellow River Estuary can be divided into three parts : Xinhekou safety area , new Laohekou hidden trouble area and Laohekou dangerous area . In the next ten years , the hidden danger area and dangerous area are faced with the potential safety hazards such as the shallow sea of the land environment caused by the continued erosion and retreat of the coastline , and the wave enhancement in the shallow sea .

Based on the theoretical research results of the interaction between power and terrain , some suggestions are put forward on the practical problems such as the alternative flow path of the Yellow River Estuary , the safety hazard caused by the rapid change of the marine environment in the offshore engineering . The urgency and necessity of promoting the design concept of the dynamic parameter of the marine engineering environment and the suggestion of early warning protection are emphatically expounded , and some suggestions such as multi - parameter design , periodic investigation and early warning protection measures are put forward .

Finally , through nearly three years of research work , this article has the following innovation points :

( 1 ) The evolution law and genesis of tidal current shear center in a complete Yellow River flow path are revealed , and the interaction relation and process of the evolution of the river mouth and the evolution of tidal current field are expounded .

( 2 ) The response law and its mechanism of the tidal current shear center in the Yellow River Estuary to the large wind process are discovered , and the new dynamic mechanism of sediment diffusion in the Yellow River Estuary is revealed from this angle , and the power mechanism of the " winter transportation " process of the river mouth is perfected .

( 3 ) The change process of the Yellow River Estuary and the ebb tide shear center under the conditions of conventional and extreme meteorological conditions is clear , and it is found that the strength of the ebb tide shear front is always stronger than that of the flood tide and its origin .

( 4 ) To study the response of the big wave to the terrain evolution during the return period of the Yellow River Estuary , and put forward the idea of dynamic parameter design and early warning protection proposal for the marine engineering environment of the Yellow River Estuary .

【学位授予单位】：中国海洋大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：P736.21

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