小水电梯级开发河段地貌单元识别与异质性分析

Identification of geomorphic unit and analysis of heterogeneity in small hydropower terrace development river sections

河流地貌单元的科学分类与识别有利于准确定位水生生物栖息地,为科学评估小水电生态影响、开展受损河流生境修复提供依据。本文根据长江一级支流大宁河1972—2016年水文数据,利用累积距平、滑动T检验、IHA-RVA等方法确定了2个水文突变点,并分析对比了变异前、变异阶段Ⅰ和变异阶段Ⅱ3个不同阶段的水文改变程度;在归纳前人分类体系的基础上,依据水文改变程度较低时段下的实地调研观测数据,结合地貌单元过程-形式关系,确定了研究区域自上游至下游R1—R8河段地貌单元的类型及其空间分布,并引入地貌单元丰富度指数(R)、密度指数(D)和多样性指数(H_(d))3个指标对研究河段地貌异质性进行了定量评价。结果表明,与变异前相比,变异阶段Ⅰ、变异阶段Ⅱ各月份水文改变度的平均值为15.53%、24.42%;R1—R4(小水电梯级开发河段)的R、D、H_(d)的平均值均小于R5—R8(较为自然段),分别相差9%、32.1%、17.2%,小水电梯级开发河段的地貌异质性有待提高。该研究定量评价了河段的地貌异质性,可从河流地貌角度为小水电分类整改工作提供决策支持。

The scientific classification and identification of river geomorphic units is conducive to the accurate positioning of aquatic habitats and provides a basis for the scientific assessment of the ecological impact of small hydropower and the restoration of damaged river habitats.Based on the hydrological data of Daning River,the first tributary of the Yangtze River from 1972 to 2016,two hydrological catastrophe points are determined by using the methods of cumulative anomaly,sliding t-test and IHA-RVA,and the hydrological change degrees of three different stages before variation,variation stageⅠand variation stageⅡare analyzed and compared;On the basis of summarizing the previous classification system,according to the field investigation and observation data in the period of low hydrological change,combined with the process form relationship of geomorphic units,the types and spatial distribution of geomorphic units in R1~R8 reach from upstream to downstream in the study area are determined,and the geomorphic unit richness index(R)is introduced Density index(D)and diversity index(H_(d))are used to quantitatively evaluate the geomorphic heterogeneity of the studied river reach.The results show that the average value of hydrological change degree in each month of variation stageⅠand variation stageⅡis 15.53%and 24.42%compared with that before variation;The average values of R,D and H_(d)of R1~R4(small hydropower cascade development reach)are less than R5~R8(relatively natural section),with a difference of 9%,32.1%and 17.2%respectively.The geomorphic heterogeneity of small hydropower cascade development reach needs to be improved.The study quantitatively evaluates the geomorphic heterogeneity of the river section and can provide decision support for the classified rectification of small hydropower from the perspective of river geomorphology.