基于遥感影像的黄河下游游荡段河势演变分析

Analysis of the River Regime Evolution in the Braided Reach in Lower Yellow River Based on Remote Sensing Images

为了研究小浪底水库运行后黄河下游游荡段河势演变情况,选取黄河下游游荡段2001-2020年近20年的Landsat卫星遥感影像图片,基于ARCGIS和ENVI软件采用边缘提取算法提取河道水边线及修正归一化差异水体指数(MNDWI)法提取水体,分析汛期河道水面宽度、汛后主流位置、汛后心滩数量等特征指标。结果表明:①小浪底水库运行后,经过20年的冲淤调整,黄河下游游荡段河势在汛期得到明显改善,主流基本归顺;②该河段河型没有明显变化,汛期水面宽度随流量同增同减,总体上逐年变宽,但夹河滩-高村河段水面宽度由于河道整治工程的控制较为稳定;③采用MNDWI法对水体的智能化提取,发现主流摆幅呈现3种规律:①主流位置基本不变②主流位置向同一个方向移动③主流位置迁徙不定;④心滩数量与流量呈负相关,总体上在2001-2007年逐年减少,2007年达到最小值13个,2007-2015年逐年增多,2015年达到最大值58个,2015-2020年又逐年减少,同时在河道河型突变位置也会发生变化。河势调整会改变河道整治工程的有效性,同时也会对滩区群众的生产生活造成影响,因此需要加强黄河下游游荡段河势的监测并对心滩的变化予以足够的重视,提升对黄河下游河势调整规律及心滩演变的认识。

In order to study the river regime evolution of the braided reach in Lower Yellow River after the operation of the Xiaolangdi Reser⁃voir,the Landsat satellite remote sensing images of the braided reach in Lower Yellow River during the past 20 years from 2001 to 2020 are selected,and the edge extraction algorithm is used based on ARCGIS and ENVI software to extract water edge and correct the normalized dif⁃ferences.The water body index method(MNDWI)is used to extract the water body and analyze the characteristic indicators such as the water surface width of the river channel during the flood season,the position of the mainstream after the flood season,and the number of central banks after the flood season.The results show that:①After the operation of Xiaolangdi Reservoir,after 20 years of dredging adjustment,the river conditions in the braided reach in Lower Yellow River have been significantly improved during the flood season,and the mainstream has basically returned.②There is no obvious change in the river shape of this reach,and the width of the water surface increases and decreas⁃es with the amount of water during the flood season,and generally widens year by year.However,the width of the water surface of the Jiahet⁃an-Gaocun section is relatively stable due to the control of the river channel improvement project.③Using the MNDWI method to intelligent⁃ly extract the water body,it is found that the swing of the mainstream presents three rules:①The position of the mainstream is basically un⁃changed.②Mainstream position moves in the same direction.③Mainstream locations are migratory.④The number of the mid-channel beaches is negatively correlated with the water volume,generally decreasing year by year from 2001 to 2007,reaching a minimum of 13 in 2007,increasing year by year from 2007 to 2015,reaching a maximum of 58 in 2015,and decreasing year by year from 2015 to 2020,and at the same time,the location of the river-shaped abrupt change in the channel will also change.The adjustment of river regime will change the effectiveness of the river improvement project,and will also affect the production and life of the people in the beach area.Therefore,it is necessary to strengthen the monitoring of the river regime in the wandering section of the Lower Yellow River and pay enough attention to the changes of the heart beach to enhance the understanding of the law of river situation adjustment and the evolution of the heart beach in the Lower Yellow River.