Dem-based Investigation on Stream Network Nodes and Their Features

Surface runoff is one of dominant factors in hydrological environment, whose spatial pattern and hydrological feature represent the composite factors of its corresponding drainage. And the stream network nodes present spatial structure and attributes of geography and hydrology in a watershed. A quantified method to analyze stream network nodes is proposed in this paper. The typical area of the Loess plateau is taken as study site and Digital Elevation Model(DEM)is chosen as basic dataset. The stream network nodes are extracted based on DEM and the classification of stream network is put out by different rules. Additionally, the basic features are analyzed from the angles of hydrology and GIS, including attribution, spatial-temporal distribution. This attempt reveals relationship between law of stream runoff and other spatial features, which has potentials to enable quantitative comparisons of different landform domestically. 1. INREODUCTION Surface runoff is one of dominant factors in hydrological environment, whose spatial distribution pattern and hydrological feature represent the composite factors of its corresponding drainage. So research on runoff and stream network is important to hydrology. And the stream network nodes present spatial structure and attributes of geography and hydrology in a watershed. Digital Elevation Model(DEM) digitally demonstrates the earth’s surface, in addition, it is the basic data source for terrain analysis and it is an effective analysis method. Now DEM is playing an important role in hydrologic and topographic character analysis. Up to the present, great progress is achieved in river network based on DEM (Horton, 1945; Tang, 2005; Liu, 2003; Jin, 2000) and it is an efficient way to extract river network (Lu, 1998; Ren, 2000; Li, 2001). Some efforts are made to derive terrain features, including peak, pit, ridge, channel, plane, and pass, based on terrain analysis (Moore, 1988; Jenson, 1988; Martz, 1988, 1992, 1995; Tribe, 1992).Moreover, the hydrographical characteristics are extracted, including stream-channel networks, delineation of catchments boundaries, catchments area, catchments length and stream order, based on the flow accumulation method (O’Callaghan and Mark, 1984).As the confluence of streams, the stream network nodes imply both geographical features and a lot of spatial-temporal messages. So, this paper proposes the concept of stream network node, probes into its features and analyzes relationship between law of stream runoff and other spatial features. 2. EXPERIMENTAL BASIS As we all know, the Loess Plateau of China has drawn worldwide attention in geographical research for its unique morphological features, abundant natural sources, most serious soil erosion, as well as its potential contribution to economic development and ecological reconstruction. Hence, from north * Corresponding [email protected] to south of the Loess Plateau, Sui De, Chun Hua and Yijunin are taken as study site, they are the typical areas which supply different types of landform and gully characteristics. Test data are the corresponding 5 m-grid resolution DEM produced according the national standard of China. 3. OBJECTIVE OF STUDY The structure of stream network is devious, complicated, so it is essential to reveal its feature. The stream network node is proposed to explore the features of stream network. The main objectives of this study are: (1) to analyze characteristics of stream network node ; (2) to reveals relationship between law of stream runoff and other spatial features With the two points being borne in mind, quantitative characterization of stream network node and analysis of their properties is carried out in this study. 4. CHARACTERISTICS AND CATEGORY OF STREAM NETWORK NODES The stream network nodes (See Figure 1) are considered as the collection of confluence of one stream and its corresponding tributaries in the drainage. For each stream network node, it contains both spatial location and hydrological attribute. But for one specific region (one drainage), stream network node can reflect the distribution of gully or stream network in different orders. The corresponding 5 m DEM resolution is taken as data source. With the support of ArcGIS the stream network nodes are extracted.