陇东合水县塬梁峁地貌分类及演化

Geomorphological classification and evolution of plateaubeam-loess hills in Heshui county of the east Gansu province

黄土地貌是按独特的演化模式形成当今复杂多样且有序分异的地貌形态组合。基于数学形态法将合水县地区黄土地貌分类并计算得出塬梁峁地貌单元的分类指标,再通过黄土地貌单元的形态特征及分类指标,对黄土塬梁峁地貌演化模式作出定量化和可视化表达,并预测塬即将消失的区域。研究发现:①似圆度是界定黄土地貌单元演化进程的重要指标,黄土地貌单元在演化过程中,其形状规律程度逐渐增加;可用周长面积比和平均坡度界定塬梁的分界,可用边界临接指数界定梁峁的分界。②塬向梁演化实质就是残塬向树杈梁演化。残塬是人类赖以生存的地貌单元,是固沟保塬工程的重点实施对象。

Loess landforms refer to the complex,diverse and orderly differentiated landform morphological combinations that are formed with unique evolution patterns.Based on analysis of mathematical morphology,this study classifies the loess landforms in Heshui county into loess plateaus,beams and loess hills,and develops corresponding classification indexes for them.Furthermore,according to morphological characteristics and classification indexes of loess morphological units,this study establishes quantitative and visual expression landform evolution models for loess plateaus,beams and loess hills,and predicts the parts of loess plateaus that are going to disappear.Roundness is found to be an important indicator to define the evolution process of the loess landform unit,and it increases as the loess landform evolution proceeds.The boundary between loess plateaus and beams can be identified by the perimeter area ratio and the average slope,while that between loess beams and loess hills can be determined by the boundary adjacency index.The transition from a loess plateau to a loess ridge actually corresponds to the evolution from a residual plateau to a branched loess ridge.It is critical to strengthen grooves and protect loess plateaus,since human beings have to rely and live on these residual loess plateaus.