黄土地貌区径流节点提取及其特征信息指数的DEM实验分析

径流节点是一种真实存在于流域单元中的地学实体对象,携带了大量的水文与地貌特征信息。针对当前研究中缺乏定量地度量径流节点所承载的地学特征信息量的相关探讨,本文结合径流节点的已有理论,总结了其地学特征信息,借鉴数学粗集理论提出了径流节点的特征信息指数（FIIRN）,并分析了相关的定义与计算方法。本文以黄土高原的7个典型黄土地貌样区5 m分辨率DEM数据为实验材料,提取了各个实验样区的径流节点,并计算了每个样区的FIIRN指数值。实验结果表明：（1）FIIRN指数可有效地映射流域单元的径流分级、发育状况等地学特征信息;（2）FIIRN指数可定量地表达流域单元的地学特征信息量;（3）FIIRN指数可作为挖掘流域地学特征信息的一个重要参数。

A Novel Index Designed for Feature Information of Runoff Nodes Based on DEM

Runoff nodes, which could be captured from every watershed on earth, are one type of the real geographical entities within the river-network. Generally, runoff nodes often locate at sites where lower grade of runoffs merging themselves into a more advanced trunk stream. It is clear that runoff nodes carry a lot of hydraulic and landform information. Although many reports have documents related to runoff nodes, the quantitative measuring researches, that concerning the geographical information of runoff nodes and taking advantages of valid theories or methods, are still rare. This may prevent people from further understanding the existence of runoff nodes in nature. Aimed to solve the aforementioned issue, this paper employs the Theory of Rough Sets (TRS) to develop a new landscape metric for perfectly characterizing the geographical features of runoff nodes. Firstly, according to current knowledge about runoff nodes, this paper extracts the potential information carried by runoff nodes. Secondly, this paper reviews some typical valid methods on how to extract runoff nodes from Digital Elevation Models (DEM). Thirdly, this paper presents the feature information index of runoff nodes (FIIRN) and illustrates the relevant computing procedures. Based on these researches and preparations, this paper carries out a case study of FIIRN for seven special regions from the Loess Plateau of China (which well represents the typical loess landscapes existed in the world). The experimental materials of DEM data are predominantly characterized with 5 meters of resolution. With the help of ArcGIS 10.1 software, this paper extracts all runoff nodes from the experimental sample regions according to their geometric features in the runoff network. Then, this paper computes the values of FIIRN using Excel 2003 and MATLAB 7.7. Surprisingly, the results show that FIIRN can effectively map the complete geographical information of a given watershed unit. Therefore, as we concluded in this paper, that FIIRN can play a valuable role for mining the information from watershed units in future. In fact, FIIRN should be considered as an optimal parameter for analyzing the morphological patterns of watershed units.