Research On Extraction Of Hydrological Elements And Building Topography Structure Of Stream Networks Based On DEM

The information of the digital watershed could reflect the distribution of river basin information and could simulate the distribution of river morphology, it is applied to hydrological forecasting, urban planning and many other areas. It is one of the core geographical data, and also is basic data of distributed hydrological model. Nowadays, for national division of distributed river basin, currently there only has concrete I level basin and II level basin division, for III level and the more refined subbasin, there is not separate basin water of partition standard published. Among the existing hydrological extraction methods, many mature hydrological analysis softwares could complete hydrological analysis automatically, but these softwares can’t generate ideal results perfectly, so it is necessary to amend and adjust the results of intermediate processes. Besides, it’s necessary to adopt the hydrologic elements that extracted and adjusted into the distributed hydrological model, this paper need to bulid some hydro-structure relationship. Therefore, this paper intends to seek out a method that could balance the efficency and accuracy of hydrology extraction and hydrology structure establishment.According to the theories of hydrology and GIS, this paper select one of I level tributaries of Yellow River--Yanhe basin as research object, and the experiment use25m resolution of DEM data to extract hydrological elements and have necessary optimization among the extraction processes of the intermediate results. For the relationship of flow concentration and establishment of topology relationship of vector hydrological elements, this paper use the extracted hydrology elements to build terrain structure and topological structure of the Yanhe watershed. The division of drainage network level and the coding drainage network can reflect topology relationship, the paper provides the underlying data that could be as reference data for distributed hydrological medel.There are the major conclusions of the paper as follows:(1) In the intermediate extraction results, there exists pseudo rivers and too short rivers. This experiment check pseudo rivers and delete these rivers with hill-shading map, and exclude too short rivers using the statistics method on length of rivers.(2) This paper use the extracted hydrological elements to build two types of watershed structure:the terrain structure and the topological structure of watershed from different aspects on division of watershed structure. The results indicate that the watershed terrain structure outweigh to reflect the external relationship of subwatersheds; the watershed topology structure focus on the confluence relationship of upstreams and downstreams. Two types both provide different reference for the establishment of distributed watershed hydrological network model.(3) With the hydrology elements of the topological relationship, to reflect the confluence among the rivers for the purpose, this paper has come up with the classification rule of drainage network, by programming this rule of drainage network and coding the drainage network and watershed automaticly with MATLAB.