基于DEM的西江磨刀门水道近40年来河床演变特征研究

Evolution of the Modaomen Channel of the Xijiang River Based on DEM during the Last 40 Years

建立了西江干流磨刀门水道1962年、1977年、1999年的DEM,研究珠江三角洲磨刀门水道近40年的河床演变。结果表明:1962—1999年磨刀门水道总体表现为冲刷状态,净冲刷量约576万m3,年均冲刷率16万m3/a,单位河长冲刷率约13万m3/km,断面面积减小,河床深槽范围扩大,平均水深、河宽均增大,宽深比减小,断面向窄深发展;但不同时段冲淤特性表现不同,1962—1977年表现为淤积,淤积量2 033万m3;1977—1999年处于冲刷状态,冲刷量2 617万m3。磨刀门水道不同阶段河床冲淤演变与流域人类活动引起的来水来沙变化、三角洲网河联围筑闸、河床采砂以及由此引起的三角洲网河水沙分配变化等因素密切相关。整体看,磨刀门水道近期演变趋势仍将表现为以冲刷为主的自适应调整。

The Modaomen channel Digital Elevation Model（DEM） was founded based on the water deep information of the history maps in 1962,1977 and 1999.With the help of the DEM,the evolution of the Modaomen channel in last forty years was simulated.The results indicated：1） Modaomen channel was general charactered by siltation from 1962 to 1977,and its total disposition quantity was 20.33×10^6 m^3;2） From 1977 to 1999,the general results was erosion,the total erosion volume was 26.17×10^6 m^3;3） From 1962 to 1999,this channel was general charactered by erosion,and the total erosion volume was 5.76×10^6 m^3,the average rate of erosion was 0.16×10^6 m^3/a,and average erosion volume per kilometer was 0.13×10^6 m^3/km.The average cross sections width and area of Modaomen channel were reduced,and the average trough area and depth were enlarged,the reach became narrower and deeper.The channel evolution was due to the result of the river discharge,the suspended sediment load and human activities in the Pearl River basin and delta networks,such as sand dredging,beach reclamation and floodgate construction.Because of these factors,the global evolution of the Modaomen channel will being erosion in the next few years.