基于DEM与数字化河道提取流域河网的不同方案比较研究

A Comparative Study on Different Schemes of Automatic River System Extraction Based on DEM and Vector Channels

基于数字高程模型(DEM)中提取流域水系是分布式水文模拟的基础与关键。然而由于DEM存在分辨率的限制和误差,而且一个流域水系河网的形成是该流域范围内的多种自然和人为因素的共同结果,并非仅取决于空间高程分布,因而由此提取出来的河网往往和真实河流分布有一定的差距。本文选择山东沂沭河流域的临沂子流域为试验区,基于该地区100米分辨率的DEM提取该流域的河网。在提取河网的过程中,引入了该地区的河道矢量图层,对主要河流进行河道强迫,通过基于高程的修正和基于流向的修正两类方法理念,利用若干不同的强迫方案,在试验流域DEM数据的基础上进行强迫作用下的河网提取。通过比较并分析不同方案的强迫效果,证明了强迫作用能使得提取的流域水系更加接近于真实河道。在本文的试验中,TauDEM模型的强迫方案2取得了最好的强迫效果。文章的最后提出了对湖泊水库强迫的一些思考和想法。

Distributed hydrologic stimulations usually integrate hydrologic models with Geographic Information System （GIS）. The foundation of the simulations lies on how to obtain hydrologic and topographic parameters from Digital Elevation Model （DEM）. Automatic extraction of river channel systems from DEM is a fundamental procedure for distributed hydrological simulations. Numerous algorithms for watershed automatic delineation based on DEM have been developed. However, Due to the errors involved in DEM, associated complex procedures in watershed delineation, and other natural and human factors determining realistic river channel systems, discrepancies usually occur between extracted river channel systems merely based on DEM and realistic channels. Additional information should be considered in traditional extraction processes in order to ensure highly reliable delineations. In this study, we explored performances of different automatic river network extraction schemes based on DEM and the information imposed in the processes. We introduced a real river channel vector map to automatic extraction based on DEM for difference schemes. Two different methods to impose the real channel vector map on DEM, namely modifying an elevation matrix or a flow direction matrix, were utilized in automatic extraction procedures. A large, complicated catchment with an area of over 10000 km2 gauged by the Linyi hydrologic station in Shandong province was selected to perform the comparisons. Results showed that imposing real channel digitized vectors on DEM greatly improved the precision of extracted river networks. In addition, we evaluated the effects of different imposition schemes on delineation results and discussed their advantages and shortcomings, respectively. These schemes included： directly decreasing the elevation of pits and combined with ESRI-ArcGIS＇ s hydrologic toolbox, the ＂AGREE＂ algorithm provided by the HEC-GeoHMS model, the AV-SWAT model＇ s ＂Burn-In＂ scheme and two different schemes provided by the TauDEM model. The ESRI-ArcGIS＇ s hydrologic toolbox and the HEC-GeoHMS use a single flow direction algorithm （SFD） while the AV-SWAT model and the TauDEM model use a multiple flow direction algorithm （MFD）, showing the latter offering better results because man-made downstream channels diverge again ：and the SFD cannot identify it. It was suggested that in general, the algorithms provided by the TauDEM model performed best. Some discussions on automatic delineations of lakes and reservoirs in large watersheds were also given.