Automated extraction of drainages in China based on DEM in GIS environment

Automated extraction the flow network and drainages is a premise of matching the observation datum and developing water cycle information system. This paper put forward a method that automatically extract drainages in China from DEM data. This method used DEM data of 1:250,000 scale. Firstly divided the whole country into 9 parts based on the drainages that extracted from 1KM DEM data; secondly filled sinks and removed peaks in each part and identified the flow direction of each cell using flow direction function, then calculated the flow accumulation of each cell according to flow direction and identified the flow network by setting the threshold value; finally used the watershed0 function to find out all the sub-drainages based on the flow networks and the watershed outlet. On the other hand, this article listed the AML code for automated extraction drainages from DEM data. Additionally the author checked the result of automated extraction using some surveyed data in Haihe drainage area. Through analysis on the comparison between the flow networks and drainage area that extracted using this method and surveyed data, a conclusion can be draw that this method is effective and efficient.