A study of landform morphologic relationships between hill slopes and gullies: taking small catchment of Wangjiagou in west Shanxi as a case

Abstract

以往坡、沟侵蚀关系研究主要限于水沙关系的探讨 ,有关原型尺度小流域坡、沟地貌侵蚀演化关系的定量研究甚少 ,尤其是坡、沟地貌特征对流域切割程度的综合影响与交互作用的定量研究尚属空白。本文在 3S技术支持下 ,根据晋西王家沟小流域 196 7年 1∶5 0 0 0正摄影像图 (DOM )、高程数字化模型 (DEM )和同期、同比例尺地形图 ,利用正交多项式回归分析方法 ,定量分析了坡、沟地貌特征对流域切割程度的影响与交互作用。研究表明 ,沟谷地在流域地貌演化及地表切割程度中起主导作用 ,在沟间地面积相同时 ,沟谷地面积约为0 1km2 是影响流域切割裂度侵蚀演化强度最大的区域 ,流域面积愈小影响流域地表破碎的程度最大。其沟道流域坡、沟地貌演化机制可用坡、沟水流动能的地貌指标的综合影响与交互作用来解释

Previous studies on relationships between hillslope and gully erosion are mainly concentrated on exploration of water and silt relations, few on quantitative studies of evolution relationships between hillslope and gully landform erosion in small catchments of original scales Quantitative studies on synthetic impact and interactions of hillslope and gully geomorphologic characteristics on catchment dissected extent are still a blank in particular This paper, supported by 3S techniques, based on 1∶5000 digital orthophotomap (DOM), digital elevation model (DEM) and topographic map of the same period and of the same scale, quantitatively analysed the impact and interactions of hillslope and gully geomorphologic characteristics on catchment dissected extent by using orthogonal polynomial regression analysis Research results indicated that gullies play a leading role in the catchment morphologic evolution and ground surface dissected extent When inter gully areas are the same, the 0 1 km 2 gully area is the maximum area affecting erosive evolution intensity of the catchment dissected extent The smaller the catchment area is, the greater the affecting extent of catchment surface fragmentation would be The geomorphologic evolution mechanism of channel slopes and gullies can be explained with synthetic impact of geomorphologic indicator of slope and gully fluvial energy Gullied land plays the leading role in affecting catchment dissected extent indicators of D r and L e , when inter gullied land area ( A p ) is constant, there exists maximum value of the dissected extent indicator L e and critical gully catchment area, the catchment dissected extent is the greatest when gully catchment area is about 0 1 km 2. The smaller the gully catchment area is, the greater the gully density would be. When inter gullied land area increases, the dissected extent indicators D r and L e decrease. When gullied land area ( A g ) keeps constant, the catchment dissected extent indicators D r and L e decrease with the increase of inter gullied land area.Catchment dissected extent is synthetically affected by fluvial erodibility under conditions of varying gradients of inter gullies and gullies and their interactions. The evolution mechanism of slope and gully landforms of gully catchment can be explained via synthetic effect of slope and gully fluvial energy landform indicators and their interactions.According to erosional characteristics of slope and gully landforms, to elevate erosional basement level is the key link for controlling modern gully head advancement and hillslope expansion rate of the catchment basins. Priorities should be given to soil and water conservation management of gully catchment area of 0 1 km 2.