基于DEM的黄土高原面积高程积分研究

Spatial variation of hypsometric integral in the Loess Plateau based on DEM

面积高程积分(Hypsometric Integral,HI)是通过统计流域地表的高程组合信息,从而揭示流域地貌形态与发育特征的重要指标。本文以1:10000比例尺5 m分辨率DEM数据分析流域面积高程积分计算时的影响因素,以SRTM数字高程模型数据为基本信息源,研究黄土高原重点水土流失区的面积高程积分空间分异特征。研究工作首先讨论并总结了面积高程积分的地学含义,明确了DEM分辨率以及分析面积对于面积高程积分计算的影响,并分析各地貌对象面积高程积分的相关性;然后,面向黄土高原重点水土流失区,采用面向多尺度分割的方法,基于小流域面积高程积分,实现了黄土高原重点水土流失区地貌分区。研究结果表明,DEM分辨率对于小流域面积高程积分计算影响较小,当小流域面积阈值达到10 km2时,面积高程积分趋于稳定;各地貌对象中,流域面—正地形—沟沿线、山顶点—山脊线—流域边界这两组组内面积高程积分值相关性非常强;基于面积高程积分的地貌分区,与黄土高原地区水土流失分区图和输沙模数分区图具有相当程度的耦合关系,并细化了原有分区结果。

Hypsometric integral is a terrain analysis factor with apparent physical and geomorphologic meanings which could reflect the landform erosion stage and evolution process. As a macroscopic parameter and method in terrain analysis, the applications of hypsometric integral could reveal the quantitative characteristic of landform evolution in catchment scale. In this paper, 5 m resolution DEMs and 3 arc-second resolution SRTM DEMs are used respectively to identify the impact factors of HI and its spatial variation in the Loess Plateau. Firstly, the geomorphologic meaning is discussed and summarized. The effect of DEM resolution and the analysis area in HI calculating is probed. With different DEM resolutions, the HI values derived could keep almost the same. When the area of catchment reaches l0 km：, the HI tends to be stable, which is regarded as a critical area for extracting HI in this study. Then, the geomorphic feature HI is proposed and the correlation of each kind of HI is calculated. There exist two feature groups in which the correlation coefficient is rather large. They are respectively catchment HI, positive terrain HI, shoulder line HI and peak HI, ridge line HI, and catchment boundary HI. Finally, the landform division based on HI is created through multiresolution segmentation in loess area. The coupling relationships exist in this division and water ＆ soil loss map, sediment transport value map. The division in this paper refines the original map to a certain extent.