摘要
长江是我国最大的河流，流域宽广、经济发达，地质地理条件复杂，加上蕴藏着丰富的水力、电力、岸线资源，一直是地质、地理、水文和工程界等研究的热点、重点和难点地区。长江皖江段为长江的下游段，为分汊型河段，矶头众多、河道复杂。五十年代以来，河岸坍塌、航道变迁、引水口及出水口淤积、沿线地区洪涝灾害层出不穷。随着三峡等大型工程的上马、运行，长江河道演变将更具复杂性。因而研究长江河道特性及其演变特征，进而在深层次上了解河道演变的影响因素，进一步从宏观上弄清河道演变的机理，是一项具有重要学术价值和巨大实际意义的研究课题。
影响河道演变的主要因素有气候、水文、地质、地貌、地质构造、科氏力及人为因素等。但这些因素对河道所起的作用是不一样的。近五十年来，地质构造、水文特别是含沙水流及人为因素对河道改造起了越来越重要的作用。而以往的河道研究大多数是通过地面调查和地形图室内对比分析来研究的(少数运用航片)，由于受人的视域范围及调查工作路线的布置的复杂度影响，对区域宏观尺度下的地质构造、长江沙洲、漫滩、阶地及河流微观领域的悬浮物等作综合性的研究便成为了瓶颈。因而对长江河型及其演变过程或多或少的产生偏差，或者不能给出一个半定量或定量的评价。
遥感技术具有大范围、多时相、多片种、多层次、含有丰富的光谱信息及具有较高的地面分辨率的特点。本文利用该技术，运用灰阶统计特征分析和主成分分析、TM741多波段融合、线性卷积增强、模型提取等一系列遥感解译分析方法，分析了断裂构造、河流地貌(阶地、漫滩、沙洲)及悬浮物等在TM遥感图象上的影像特征，解译出了安徽南部断裂构造格架、河流地貌和悬浮物的分布，并新解译出了9条近东西向的断裂。在此基础上，分析了各影响因素对河道的影响作用。
结果表明，皖江河道演变是各种因素综合影响的结果：河流地貌岩性提供了河道演变的基础和条件，气候影响着来水来沙。自北向南的构造掀斜运动造成了河道自北向南移的特点。北东向断裂构造控制了皖江河型的展布；东西向断裂构造影响河道的拓宽，形成矶头，矶头挑流进一步使河道形成稳定的鹅头型；北西、南北向断裂影响局部河道的发育演变，如北西向庐江-钟鸣断裂影响铜陵沙洲的发育演变，南北向断裂影响枞阳、铜陵、获港河道使其延伸方向由北东转向南北向。地质构造还在根本上控制着地形水系，因而控制着皖江流域格局，最终通过改变汇水汇沙条件、边界条件而得到反映。这就说明了皖江河道演变是适应于地质构造的。河道的微观水流，特别是悬浮物(主要是悬浮泥沙)反映输沙水流淤积特性，总是在流速缓慢、易回流的地方淤积、形成新生沙洲，为正在发生及将来发生的河道淤积和演变打下基础。
同时，在结合河道资料及多数据源资料对比分析的基础上，对长江安徽段河道历史时期的演变及近五十年来的演变进行了分析研究。认为历史时期皖江河道演变具有如下特点：①长期以来河道主汊向右岸摆动；②局部河道往复摆动；③河流曲折度增大；④在局
部地段河道向左摆动;⑤古分流河道逐渐消亡。而近五十年以来河道呈现出以下新的特点:
①重点河段的岸线的平面变形向左，如芜湖大拐，1954·1975年，左岸后退率38.6 In/a，
而在1975一2000年间，后退率仅为15.4 In/a;②鹅头形分汉河段继续保持周期性演变;③
局部河流段有的曲折度增大，有的减小，但总的安徽段主流线长度基本保持不变;④人为
作用影响越来越大，人为堤防的修建限制了河道的摆动，但也造成河道束窄而使岸线冲刷
加快，导致崩岸频繁。
总之，运用遥感技术来解译河道演变的影响因素的相关信息，结果可使河道演变的分
析从定性走到半定量、定量评价，从指示要素分析到综合分析，从单一解译到结合地形图
等综合方法互补。从而更加深刻的揭示了河道演变的影响因素。也在深层次上把握了河道
演变的机理。为岸带开发、合理决策提供了科学依据。
With large valley, developed economy, complex geological and geographical condition, abundant waterpower and power resources, and longest shores, Yangtze River is the biggest river in China and is regarded as a important and difficult hot region in the geology, geography, hydrology and engineering realm. The part of river in Anhui stands in the lower of the river and is diverged river. There are a lot of nodes and complex river course. Since 1950s, riverbank collapsed, river course changed, inlets and outlets of the river were silted up and the flood pile up one after another. With the operation of Three Gorge Project, riverway will be more complex. So researching the characteristic and the evolution of Yangtze River riverway, understanding the influences on the evolution of Yangtze River course, further to studying the evolution mechanism of the river, are important in science research and actual application.
The influence factors of the river course evolution include climate, hydrology, geology, geological tectonic, Colioli Force, and human activity, and their functions are different, and they are more and more important in the last 50 years, especially water current containing sand, and human activity. However, people studied the riverway mainly by field survey and landform map contrast before. Because of the limits of man's field view and complexity of field survey route, it is a difficult bottle neck for people to make synthetical analysis on geological structure, Yangtze river shoal, floodplain, terrace, and microcosmic suspended load on macroscopical scale. So the results of the evolvement of the riverway concluded by above mentioned methods are more or less different from its actual evolvement, and the estimate is not quantitative.
On the basis of Remote Sensing technique's good characteristic with large-area, multi-time, multi-photograph variety, manifold abundant spectral information and high ground resolution, the fault tectonics frame,river geomorphy (such as terrace, floodplain, shoal, etc) and suspended load, etc. were explained after analyzed the fault tectonics, river geomorphy, characteristic in the TM image by gray bar statistics, primary component analyses,TM741 image integration, line convolve enhancement and model recognition etc. especially 9 piece of fault tectonics were explained in this thesis, in succession, the impacts of the factors severally were analyzed.
That is, the evolvement of Anhui reach of Yangtze River was influenced by many kinds of factors: geomorphy is the elementary factor, and climate influence water and sand offered by river basin. Structural movement of earth crust from north to south cause the riverway move from north to south. Northeast faults control the spread of the Anhui riverway, and eastwest faults resulted in the widening of the river and the occurrence of nodes, then the stream raised and the riverway turn into goose pattern braided river. Northwest faults and Northsouth faults influence the evolvement of partial riverway, for example, the northwest Lujiang-zhongming fault influence the evolvement of Tongning shoals, and the northsouth faults passing through
Zongyang-Digang make the riverway's direction from North-east to North-south. In a word, the geological structure controls the terrain and water system radically, then control the river basin pattern, which is reflected on condition of the changed coming water, sands and its boundary. That's to say, the evolvement of Anhui riverway is adapted to the geological structure. In addition, the microcosmic stream, especially suspended load (mainly suspended soils and sands) reflected on the characteristic of transported sands' streams, and always silt up and form shoal in the place where the stream velocity is lower and river steam return easy. And prepare for the being and coming riverway evolvement.
Simultaneously, based on the contrastive analysis of data on the river, we studied the evolvement of the Anhui riverway, in historical epoch and especially in the past 50 years. Characteristic of the evo
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