天山北麓流域面积高度积分特征及其构造意义

提取了天山北麓河流水系流域的常规地貌计量指标（盆地大小、面积和高差）以及面积高度积分,通过对流域面积高度积分曲线形态特征、面积高度积分值的分析,结合区域地质构造活动,探讨了面积高度积分对板内再生造山带新构造活动的指示意义以及天山北麓流域的地貌发育过程。研究表明,北天山流域的次集水盆地面积高度积分与次集水盆地的面积和高差都没有相关性,堆积作用和轻微构造抬升作用都会影响冲积扇区次集水盆地,使其面积高度积分值偏高。河流面积高度积分曲线形态和面积高度积分值在空间分布上的差异,反映了天山北麓3排逆断裂褶皱带的不同的构造活动特征。面积高度积分曲线的循环形态特征,揭示了强烈构造运动与河流剥蚀作用影响面积高度曲线形态发育的动态演绎过程。     

空间自相关分析在面积高程积分中的应用

面积高程积分值(HI)作为揭示区域构造相对活动性的指标,在地貌学中得到了广泛的应用。传统的研究多以流域作为载体分析HI值的特性,然而HI值是否受流域大小及形状的影响存在争议。以白龙江流域作为试验区,利用ASTER 30 m及SRTM 90 mDEM数据,基于不同大小的分析窗口分别计算了流域的HI值。研究表明:1.原始HI值没有明显的空间分布格局,受分析窗口空间分布位置、DEM分辨率、岩性差异的影响不大,但是受分析窗口大小的影响较大,存在尺度依赖。2.对原始HI值进行空间自相关分析后HI值表现出强的空间自相关性,且"热点分析"表明HI值高值聚集区分布在白龙江中上游,与地壳隆升强烈及断裂活跃的作用相关,低值聚集区分布在白龙江下游及一些河谷中。研究表明,空间自相关分析的应用,能够使基于分析窗口提取的HI值呈现出更多的构造意义。     

格尔木河流域面积-高程积分值的地貌学分析

在sRTM-DEM数据的基础上,运用GIS空间分析技术,系统提取了格尔木河三级流域及部分二级流域地形参数和面积-高程积分值,探讨了面积-高程积分值的面积及空间依赖性,并对面积-高程积分值(HI)对构造活动性、岩性变化、冰川作用强度的指示意义进行了研究.研究表明:HI值具有面积依赖及空间依赖性;东昆南断裂(F4)-西大滩断裂(F3)以昆仑山口为界可以分为东西两部分,各自的活动性都是中间强往两边依次减小,东昆中断裂(F1)的活动性变化不大;岩性对HI影响表现出,侵入岩的抗侵蚀力最大,片岩的抗侵蚀力最小,碳酸盐岩组合的抗侵蚀力居中;冰川作用对地貌发育和侵蚀程度有改造作用,与只有古冰川发育或无古冰川流域比较,有现代冰川发育,古冰川作用遗迹广泛的流域,HI值较大并会出现U型谷.     

北天山流域地貌特征及其构造活动分析

以流域为单位计算地貌参数有助于分析区域构造活动。该文以北天山山区为研究区,将其划分为805个流域,提取地势起伏度(RA)、分形维数(FD)、河流阶梯指数(SL)、面积-高程积分(HI)、圆度比(Rc)5个参数,并以此为基础构建相对构造活动强度(IRAT),以此分析北天山流域地貌特征及构造活动强度。研究表明北天山不同地貌分区内呈现不同地貌特征,高山区地势起伏度及河流阶梯指数整体较大,河谷区圆度比变化较大。相对构造活动强度空间分布表明,研究区域中间部分构造活动较为活跃,自中部向东西两侧,强度逐渐降低;低山丘陵区中,准噶尔南缘断裂带所在区域构造活动强度更高。以流域地貌指标反映的构造活动强度分布与地壳构造变形位移场所计算结果较为相似。     

贺兰山水系流域数值地貌特征及其构造指示意义

基于Arcgis9.3与ASTER GDEM数据,提取了贺兰山两侧主要水系及其流域边界,根据河流及流域指标提取河流纵剖面、流域的Strahler曲线,并计算其面积高度积分值（Hypsometric Intergral）、河流纵剖面的凹度值（Concavity）。通过HI值、凹度值同河流落差、河流长度、流域面积之间相关性分析发现,后3种地貌参数与HI值、凹度值间的相关性较差。对比分析贺兰山两侧河流HI值及凹度值发现：贺兰山东侧北段活动性大于南段,西侧构造活动性分布规律不明显。结合9条河流所处流域的Strahler曲线、河流纵剖面形态和HI值、凹度值分析发现：汝箕沟及其以北贺兰山地区处于地形演化的老年期,汝箕沟以南贺兰山段处于均衡调整的壮年期。     

渭河水系流域地貌特征及其成因分析

为了研究渭河水系流域地貌特征及其成因,以SRTM-DEM为基础数据,运用ArcGIS软件平台从DEM数据中提取渭河流域内独立的65个小流域,其中43个位于北岸,22个位于南岸;然后划分盆地等级,计算每个流域单元流域的面积、周长、河流总长、形状指数、平均坡度、相对高差以及高程-面积积分值和水系分支比等。通过对流域地貌参数以及高程-面积积分值和分支比等特征参数的分析,发现渭河南北两侧水系和亚流域的发育具有明显的不对称性。成因分析显示,渭河水系的这种特点虽与气候和岩性有关,但新生代以来自北向南的构造掀斜隆升作用是造成渭河流域南北差异特征地貌的主要原因。这些特征指示了渭河水系南北两侧晚新生代构造活动的差异性,反映了秦岭造山带晚新生代以来发生自北向南的掀斜隆升作用。     

基于面积−高程积分的他念他翁山玉曲流域地貌学分析

以他念他翁山玉曲流域为研究区,利用ArcGIS中的水文分析工具,将玉曲流域划分为1 030个亚流域盆地,采用高程起伏比法,对亚流域盆地进行面积?高程积分值（HI）计算。结合研究区的构造运动、岩性、地形起伏度、冰川作用等,探讨HI值的分布特征及主要影响因素,并确定研究区的地貌演化阶段。研究结果显示：① 玉曲流域所有亚流域盆地的HI值介于0.18~0.70,HI平均值为0.44,整体处于侵蚀循环的壮年和老年阶段。② 长毛岭大断层和瓦合大断裂经过玉曲流域,2条断裂的HI平均值分别为0.47和0.42,长毛岭大断层的活动性要高于瓦合大断裂,说明构造因素对HI值存在一定影响。③ 由于不同亚流域盆地内岩性抗侵蚀能力不同,导致HI值存在着较大差异,花岗岩、闪长岩等侵入岩（平均值0.55）>砾岩、灰岩等沉积岩（平均值0.49）>海相碳酸盐岩（平均值0.47）>夹杂着粉砂岩、页岩和泥岩的长石石英砂岩（平均值0.42）>第四系冲积物和冰碛物（平均值0.35）。④ 对于玉曲流域而言降水量对HI值的影响较小。     

基于DEM的黄土高原面积高程积分研究

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。     

基于DEM数据的北天山地貌形态分析

基于SRTM3-DEM数据,运用GIS空间分析技术,通过面积-高度积分、地形高程(平均高程、最大高程、最小高程)、地势起伏度及地形剖面线方法,对北天山的地貌特征进行了初步分析。结果表明,北天山山势险峻并且呈NW-SE走向,显示天山受南北向水平挤压隆升作用。近S形的面积-高度曲线、偏高的面积高度积分值表明北天山地区处于构造活跃时期,地貌发育属壮年期的早期阶段。地形高程剖面线揭示了北天山存在3级夷平面地貌特征,地势起伏度变化幅度最大地区则是受陆内挤压构造应力影响地形抬升最强的地区。     

西藏玛旁雍错流域冰川与湖泊变化及其对气候变化的响应

利用遥感和地理信息系统技术,基于1974,1990,1999和2003年4个不同时期的遥感影像,包括Landsat系列影像,ASTER影像和地形图,研究了玛旁雍错流域(面积7786 km²)内冰川与湖泊的变化及其对气候变化的响应。研究结果表明,由于气候变暖,在过去30年里该流域冰川和湖泊都以退为主,有进有退。自1974年到2003年,冰川面积从107.92 km²减少到100.39 km²,冰川退缩明显加速。由于年降水量减少、蒸发量增大,30年中湖泊总面积从782.24 km²减少到748.08 km²。湖面的缩小与扩涨都在加速,尤其是小湖泊变化更明显,湖泊的加速变化可能是青藏高原高海拔内陆流域水循环过程加速的表征之一。     

六棱山北麓中段冲沟地貌发育的定量研究及其新构造意义

利用地貌形态指标对六棱山北麓断层中段的5条冲沟进行定量化研究,流域的冲沟比降指标(SL)、面积--高度积分值(HI)和流域盆地形态因子(Bs)的异常值表明5条冲沟的发育对六棱山北麓断层活动性有明显的响应,流域发育处于壮年期.秋林沟口野外实测数据验证并揭示了六棱山北麓断裂晚第四纪以来的活跃性.     

River and basin morphometric indexes to detect tectonic activity: a case study of selected river basins in the South Indian Granulite Terrain (SIGT)

Abstract

The effects and influence of tectonic processes on the Anjarakandy, Thalassery, Mahe, and Kuttiyadi watersheds and rivers of the South Indian Granulite Terrain in Kerala were examined to determine their spatial heterogeneity. Drainage basin asymmetry (Af), transverse topographic symmetry factor (T), hypsometric integral and curve (HI), longitudinal profile, stream length gradient index (SL), and stream concavity index (SCI) suggest heterogeneity in tectonic influence. Clusters of geomorphic anomalies in similar lithology rule out lithologic control on drainage development. However, the orientations of the drainage networks and predominant fractures/lineaments compare closely and reveal strong tectonic influence. Though the watersheds are considered to be in an advanced stage of erosion by the low HI (<30) and high values of SCI, variations in the shape of the hypsometric curves and differences in the SCI values indicate the different influence of tectonic process from watersheds in the north to the south. Among the watersheds, the Mahe and Kuttiyadi are more sensitive to tectonic processes than the Anjarakandy and Thalassery and indicate spatial heterogeneity in the influence of tectonic activity, confirming the grouping of watersheds based on structural and drainage patterns.     

The sensitivity of East African rift lakes to climate fluctuations

Sequences of paleo-shorelines and the deposits of rift lakes are used to reconstruct past climate changes in East Africa. These recorders of hydrological changes in the Rift Valley indicate extreme lake-level variations on the order of tens to hundreds of meters during the last 20,000 years. Lake-balance and climate modeling results, on the other hand, suggest relatively moderate changes in the precipitation-evaporation balance during that time interval. What could cause such a disparity? We investigated the physical characteristics and hydrology of lake basins to resolve this difference. Nine closed-basin lakes, Ziway-Shalla, Awassa, Turkana, Suguta, Baringo-Bogoria, Nakuru-Elmenteita, Naivasha, Magadi-Natron, Manyara, and open-basin Lake Victoria in the eastern branch of the East African Rift System (EARS) were used for this study. We created a classification scheme of lake response to climate based on empirical measures of topography (hypsometric integral) and climate (aridity index). With reference to early Holocene lake levels, we found that lakes in the crest of the Ethiopian and Kenyan domes were most sensitive to recording regional climatic shifts. Their hypsometric values fall between 0.23–0.29, in a graben-shaped basin, and their aridity index is above unity (humid). Of the ten lakes, three lakes in the EARS are sensitive lakes: Naivasha (HI = 0.23, AI = 1.20) in the Kenya Rift, Awassa (HI = 0.23, AI = 1.03) and Ziway-Shalla (HI = 0.23, AI = 1.33) in the Main Ethiopian Rift (Main Ethiopian Rift). Two lakes have the graben shape, but lower aridity indices, and thus Lakes Suguta (HI = 0.29, AI = 0.43) and Nakuru-Elmenteita (HI = 0.30, AI = 0.85) are most sensitive to local climate changes. Though relatively shallow and slightly alkaline today, they fluctuated by four to ten times the modern water depth during the last 20,000 years. Five of the study lakes are pan-shaped and experienced lower magnitudes of lake level change during the same time period. Understanding the sensitivity of these lakes is critical in establishing the timing or synchronicity of regional-scale events or trends and predicting future hydrological variations in the wake of global climate changes.     

Hypsometric Analysis of Headwater Rock Basins in the Dolomites (Eastern Alps) Using High‐Resolution Topography

Hypsometric curves and integrals are effective tools for rapid quantitative assessments of topography. High‐resolution digital terrain models derived from airborne LiDAR data have been analysed to study the hypsometry of small headwater rock basins (drainage areas up to 0.13 km²) in three study areas in the Dolomites (Eastern Alps) that have similar lithologies and climatic conditions. Hypsometric curves in the studied rocky headwaters display a variety of shapes and present remarkable differences between neighbouring basins. Hypsometric integrals show generally high values in the three study areas (>0.42, mean values between 0.51 and 0.65). The extent of the scree slopes located at the foot of rock basins in the three study areas is larger in the area with lower hypsometric integrals and indicates consistency between the development of basin erosion, which is shown by the hypsometric integral, and debris yield, represented by the extent of scree slope. No clear relations were observed between the hypsometric integrals and basin area and shape. When extending the analysis to larger basins, which encompass rocky headwaters and downslope soil‐mantled slopes, a negative correlation is found between the hypsometric integral and catchment area, suggesting that the scale independency of the hypsometric integral occurs essentially in headwater rock basins. Geomorphometric indices (residual relief and surface roughness) have contributed to interpreting the variability of surface morphology, which is related to the geo‐structural complexity of the catchments.     

Changes in the hypsometric curve through mountain building resulting from concurrent tectonics and denudation

The stages of geomorphic development of mountains have sometimes been explained based on Strahler's diagram of hypsometric curves. Although the Japanese mountains are young, they do not follow his diagram. Hypsometric curves, simulated using empirical laws deduced from the Japanese mountains, indicate that mountain building resulting from concurrent tectonics and denudation does not produce convex curves but concave and/or s-shaped curves. The hypsometric curve of a mountain changes from a concave curve to an s-shaped curve in accordance with the increase in mountain altitude. The succession of the hypsometric curve during concurrent tectonics and denudation is the reverse of Strahler's diagram. The hypsometric integral increases with the advance in stage which is evaluated based on the change in mountain altitude. It has a relatively good correlation with the stage. However, the sequence of change in the hypsometric integral is different according to the extent of the terrain examined, whether the terrain is restricted to the interior of a mountain or pertains to the whole mountain, and whether it includes newly emerged land. The stage should be evaluated based on the course of change in the integral characteristics for the extent of the mountain examined.     

陕北洛河流域地貌演化阶段的定量分析

根据洛河流域地貌南北纵向区域分布规律,并参考张宗祜先生(1986)编制的"中国黄土高原地貌类型图",将洛河流域由南至北依次划分为洛川黄土塬区、甘泉一志丹黄土梁状(为主)丘陵沟壑区及吴起黄土峁状(为主)丘陵沟壑区3个地貌区。借助于GIS的空间分析功能,对洛河流域3种不同地貌绘制了Strahler曲线,采用高程积分法、信息熵法、侵蚀积分值法进行计算。结果表明:3种地貌区均属于壮年期地貌发育数量特征值范围,说明洛河流域总体的发育状态已经开始进入壮年期,但不同地貌分区的发育阶段不尽相同;洛河流域不同地貌的面积-高程积分曲线的S值大小排列顺序为:吴起黄土峁状(为主)丘陵沟壑区< 洛川黄土塬区< 甘泉一志丹黄土梁状(为主)丘陵沟壑区,与理论情况不相符。分析认为,这可能是由于近年来洛川黄土塬区侵蚀强度增加对洛川黄土塬区的地貌发育产生了一定的影响。     

中条山北麓河流地貌参数及其新构造意义

基于数字高程模型（DEM）及地理信息系统（GIS）技术,系统提取和分析了中条山北麓河流坡降指标、河道陡峭指数及面积高程积分等河流地貌参数。研究表明：河流坡降指标、河道陡峭指数及面积高程积分在永济至解州一带表现出较高的值;综合分析岩性、降水及构造等因素可知,新构造运动是控制中条山北麓河流地貌发育的主要因素,自北向南总体表现出增强的趋势,在永济南活动最强。前人研究表明,中条山北麓断裂晚第四纪以来构造活跃,全新世以来仍有多次活动,但不同部位活动强度各异,解州段晚更新世晚期以来滑动速率相比韩阳段及夏县段高,极高值在出现在永济南一带。可见,基于河流地貌参数获得的中条山北麓新构造运动强弱与断裂晚第四纪以来的活动强弱一致。