【作者】 邓金运；

【导师】 李义天；

【作者基本信息】 武汉大学 ， 水力学及河流动力学， 2003， 博士

【摘要】 洪水灾害一直是中华民族的心腹大患,随着人类活动的加剧,泥沙成为制约洪灾的重要因子,水灾和沙灾共同作用,组成了水沙灾害。进入90年代以来,洪灾出现了小流量高水位、大面积大范围等新特征,水沙灾害更加频繁,而且随着经济的发展和人类活动的加剧,水沙灾害带来的风险也越来越大。因此,研究水沙灾害的形成过程和机理,对于水沙灾害的防治具有重要的意义。目前流域水沙灾害的研究不足有:局部区域(河段)泥沙运动机理和流域地貌系统的研究较多,而将泥沙运动纳入流域系统考虑的较少;关于流域泥沙运动形成机理或将流域系统中各区域泥沙运动关联起来考虑的研究较少;关于泥沙自身运动规律的研究较多,关于泥沙运动引起江河洪水灾害过程的研究较少;定性的规律研究较多,定量的研究较少。研究水沙灾害要涉及到水沙输移的各个方面,不论是水土流失还是洪水灾害均是通过水沙产输变化表现出来的,而其他众多的直接的或次生的水沙灾害,同样和水沙输移有着千丝万缕的联系。由于泥沙运动具有累积性、群发性、链发性等特点,水沙的输移易形成全流域的灾害链和各种复合灾害。从上游的山地灾害(滑坡、泥石流)、水土流失、水库的淤积;中下游的湖泊萎缩、洪涝灾害;河口的港口淤积、海水入侵;以及沿江两岸环境的恶化,流域泥沙产、输、积已成为一系列自然灾害触发的关键驱动因子。因此,流域水沙输移是水沙灾害的形成前提和基础,水沙输移过程的研究是水沙灾害研究的关键问题。如前所述,流域的水沙输移变化造成了目前水沙灾害的新形势,模拟和预测流域的水沙输移变化过程意义重大,但目前流域水沙输移存在的主要问题是:由于流域涉及面积较大,模拟的时间和空间尺度也相应要求较大,以及由于研究方法的局限和全流域水沙模拟框架或体系的欠缺,进行全流域综合模拟存在困难。目前水沙灾害的主要研究方法有:资料分析的方法、地学的方法、水文学的方法、水动力学的方法等。上述各种方法都有其自身的优势,同时也存在着缺陷。直接应用其进行大范围的水沙灾害问题研究存在一定的局限性。因此,前人的大量工作多是基于水文的方法,集中在小流域或区域的洪水模拟,全流域的洪水模拟尚不多见,而全流域的水沙输移模拟或泥沙模拟则是空白,急需进行深入的研究。为了进一步深入研究流域水沙灾害,针对上述水沙灾害研究的不足和流域水沙输移模拟的需要,迫切要求创建流域水沙模拟框架,在此基础上建立流域水沙输移模型来综合上下游水沙变化,研究水沙灾害形成机理。本文正是从这种需求出发,立足流域的观点,提出了流域水沙模拟的新思路和研究框架,通过划分流域不同计算单元、多方法联合运用以及多模型集成的途径建立了全流域水沙输移模型。在水沙灾害研究方法上取得了进展。同时,利用本文建立的流域水沙输移模型,对长江上中游流域水沙输移机理进行了系统的研究。通过联合流域上游和中游分析水沙输移变化,得到了一些有意义的结论。论文共分为两部分:第一部分主要是流域水沙输移模型的建立,第二部分主要是将模型应用到长江上中游流域研究水沙灾害的形成机理。论文共分为五章,各章内容如下:第一章阐述了本文所研究问题的起源、背景和研究意义,总结分析了目前水沙灾害形成机理研究的现状和研究方法的进展,认为随着水沙灾害研究的深入,单纯的洪水模拟难以反映天然的、真实的情况,局部的小区域的水沙模拟不能反映流域上下的连接和响应机理,全流域的水沙输移模拟势在必行。但目前这方面的国内外研究较少,没有成熟的经验和模式可以借鉴,迫切需要研究。针对这一主要问题,拟订了本文的主要研究内容。第二章从流域水沙输移的特点出发,针对目前研究的不足和存在的主要问题,提出了流域水沙模拟的新思路和框架,通过划分流域不同计算单元、多方法联合运用以及多模型集成的途径建立了全流域水沙输移模型。在水沙灾害研究思路和方法上取得了进展。流域水沙输移模型的建立,从宏观流域出发,突出了上下游的联系,避免了单一模型割裂流域水沙输移互连关系、不能反映整体变化的矛盾,提供了全流域水沙灾害研究的有利工具。在模型的建立过程中,考虑了各方法存在的缺陷,并相应的进行了改进:传统BP算法的核心是利用链导数法则将误差函数对连接权的一阶导数从输出层向输入层反向传播,然后由这些导数按梯度下降法修改权重。由于在极小值附近误差对权的一阶梯度趋近于0,因此该算法在极小值附近收敛速度较慢。本文采用联合梯度算法来解决局部极值问题,并通过试算法解决隐含层不易确定的问题;以往对水库调度模型的研究,多是防洪、发电、水库淤积等方面单独计算,本文综合考虑防洪、发电情况,建立了综合考虑防洪、发电调度的水库模型,结合水库泥沙淤积计算,形成了水库水沙调度模型;一维水沙数学模型需要解决的问题是求解非恒定流圣维南方程组的计算工作量太大、求解悬移质泥沙运动方程计算精度要求较高,本文通过Preissman四点偏心隐格式的线性化的方法对圣维南方程组进行离散,通过相临时层之间用差分法求解,在同一时间层上求解析解的办法对悬移质泥沙运动方程进行离散,提高了计算速度。第三章在总结目前对长江上中游水土流失、水沙产输研究的基础上,从定义、类型、状况、影响因素、对水沙灾害的影响等方面对长江上游水土流失进行了全面的研究;在此基础上,对水土流失后泥沙的侵蚀、输移、堆积过程进行了探讨,从上游各子流域产沙方式、产沙区分布、泥沙输移比变化、工程拦沙效应等方面对各子流域产流产沙进行了系统研究,估算了宜昌无水库拦沙情况下沙量变化,指出长江上游大量泥沙的淤积是整个流域的潜在威胁,对中游具有重要的影响。对长江中游水沙输移规律的研究,从江湖历史演变、近期进出口和区域内部水沙输移变化进行了宏观分析,得到中游水沙灾害加剧的原因是近期中游各区域泥沙淤积部位的改变造成的,城陵矶~汉口河段的大量淤积是造成小流量高水位现象的重要原因等认识,对泥沙淤积造成螺山洪水位变化以及引起的洞庭湖调蓄量变化等进行了定量的研究,研究表明:在1977年典型水沙条件下,螺山处河床每抬高1m,相应的水位抬升约0.56m;提出了调蓄量的定义、计算方法,得到了洞庭湖调蓄量自50年代到90年代逐渐增大等认识。第四章将流域水沙输移模型应用到长江上中游流域,将上游和中游有机的联系起来综合研究。首先结合长江上中游的实际情况,通过简化,针对不同计算单元分别建立了基于人工神经网络的上游产流产沙模型、综合考虑防洪、发电的三峡水库水沙调度模型、中游河道一维水沙模型、洞庭湖水沙经验模型,并按结构集成为长江上中游水沙输移模型。利用建立的模型,分析了目前长江上游不同来源水沙对宜昌沙量的影响以及三峡建库前后中游各区域对上游水沙变化的响应,认为上游大量来沙将引起中游宜昌～城陵矶、城陵矶~汉口、洞庭湖区三大区域的泥沙交换和转移,三峡建库后拦截了本该进入长江中游的大量泥沙,减轻了中游的泥沙负担,为水沙灾害的防治赢得了至少50年的时间。并最后给出了长江流域的水沙灾害的防治策略。第五章是全文的总结和展望。总结了全文的研究成果,并对今后的工作进行了展望。本文流域水沙输移模型的建立,提供了全流域水沙输移研究的思路和工具,通过应用到长江上中游流域的研究表明:该模型能很好的反映流域各区域、不同计算单元之间水沙输移变化过程,通过多种方法的综合运用,解决了流域模拟时空尺度大、模拟方法存在局限的问题,满足宏观水沙灾害机理研究的需要。5科研成果: (1) Deng Jin-yun, Li Yi-tian. Numerical modeling of channel equilibrium profile and its effect on flood control. Journal of Hydrodynamics, Ser.B, 1(2002), p93-99. (2)李义天、邓金运、孙昭华、李荣,泥沙淤积与洞庭湖调蓄量变化,水利学报,2000年12月第12期,p48-52 (3)李义天,邓金运,孙昭华,长江流域自然生态环境破坏与水沙灾害的关系,水土保持学报,2002年第16卷第6期,p31-35 (4)李义天,邓金运,孙昭华,黄颖,输沙量法和地形法计算螺山汉口河段淤积量比较,泥沙研究,2002年第4期,p20-24 (5)李义天,邓金运,孙昭华,何用.洞庭湖调蓄量变化及其影响因素分析,泥沙研究,2001年12月第6期,p1-7 (6)邓金运,李义天,平衡纵剖面数值试验研究及其对防洪的影响研究,水动力学研究与进展,2002年A辑第17卷第3期,p304-310(7)黄颖,邓金运,孙昭华,围垦和淤积对洞庭湖调蓄量的影响,武汉大学学报(工学版),2002年第35卷第2期(8)李义天,何用,邓金运,孙昭华,多因素作用下的洞庭湖洪水调蓄量变化,安全与环境学报,2001年第1卷第6期,p26-30.更多还原

【Abstract】 Chinese people have being suffered by the flood disaster. With the development of human activity, sediment has been an important factor that affects the flood disaster. The sediment disaster and water disaster combine the water and sediment disaster. Since 1990s’, the new features of the flood disaster happened such as small discharge and high water level, big area and large range and so on. With the development of economy and human activity, the risk caused by the water and sediment hazard will increase. It is of important value for the prevention and control of water and sediment disaster to study the forming process and mechanism.The study of water and sediment disaster includes different aspects of water and sediment transport, all the disasters such as soil and water loss and flood disaster and so on are reflected by them. Because of the sediment motion features of accumulation, group generation, chain generation, the disaster chain and the integrative disasters in the whole basin can be formed through the water and sediment transport, which includes water and sediment loss, reservoir deposition in the upper basin and channel deposition, lake shrinkage in the middle and downstream basins and so on. The sediment yield, transport and accumulation in the basin have become the critical factor. So the basin water and sediment transport is the premise of forming water and sediment disaster. The study on water and sediment transport process is the key problem of studying water and sediment disaster. Based on the previous conditions, according to the insufficiencies of existed studies, this paper presents a new idea and a frame of basin water and sediment simulation. The basin transport model of water and sediment is established by the approach of dividing the basin into different calculated units, applying several associated methods and combining many models. The transport mechanism of basin water and sediment in the middle and upper reaches of the Yangtze River is studied systematically by using this model. Some conclusions are obtained through analyzing the transport changes of water and sediment in the middle and upper reaches.In the first chapter the origination, background and significance of the topics are described. The recent research status and the current advances of the research methods of the forming mechanism of water and sediment disaster are summarized. With the development of water and sediment disaster, the single flood simulation is difficult to reflect the natural and true situation. The partial water and sediment model can’t reflect the conjunction and response mechanism between the upper and downstream basin. The transport simulation of water and sediment in the whole basin is necessary which is studied rarely at home and abroad without the good examples using for reference. The main research contents are summarized in the end of this chapter.In the second chapter, according to the feature of the transport of water and sediment, the disadvantages of the present researches and existing problems, the transport model of basin water and sediment is established. The model shows the relation between the upper and downstream reaches based on the macro basin and provides an advantageous tool to study the water and sediment disaster in the whole basin.In the third chapter, on the basis of reviewing the present studies on the soil and water loss and water sediment yield in the middle and upper reaches of the Yangtze River, the soil and water loss in the upper reaches of the Yangtze River is researched comprehensively on the definition, types, status, influence factors and impact to the water and sediment hazard. Then, the process of sediment erosion, transport and deposition are studied preliminarily after soil and water loss. The transport law of water and sediment in the middle reaches of the Yangtze River is studied on the historical evolution process of river and lake, the transport change of water and sediment in different regions. The increasing water and sediment disaster in the middle reaches are caused by the recent change of sediment deposition in those different regions. The large sediment deposition in Chenglingji to Hankou reach is an important factor that caused the phenomenon of small discharge and high water level. The quantitative study on water level change at Luosan and the flood storage capacity in Dongting Lake caused by sediment deposition are given in this chapter.In the fourth chapter, the basin transport model of water and sediment is applied to study the mechanism of water and sediment in the middle and upper basins of the Yangtze River. According to the factual situation and varied units, the different simplified models are established such as water and sediment yield model using ANN method, the water and sediment regulation model benefiting to flood control and electricity generation in the three Gorges Reservoir, 1-d model of water and sediment in the middle reach of the Yangtze River, the empirical model of water and sediment in Dongting Lake and so on. Those models are integrated to the basin model of water and sediment. The impact of the different water and sediment sources in the upper Yangtze River to the sediment amount in Yichang station, the response of the different regions in the middle reach to the changes of water and sediment in the upper reach of Yangtze River before and after the construction of TGP are analyzed by the established model. In the end of the chapter, the prevention and control strategy of water and sediment disaster in the Yangtze River basin is presented.The conclusion and prospect is given in the fifth chapter.更多还原