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1.
天山北麓河流纵剖面与基岩侵蚀模型特征分析 总被引：2，自引：0，他引：2
本文提取分析天山北麓10条河流的纵剖面,通过函数拟合纵剖面形态特征,同时运用基岩侵蚀力模型来研究河流纵剖面形态的发育演化过程,来揭示河流纵剖面的发育与构造活动之间的内在关系.研究表明:天山北麓河流地貌地形发育阶段处于河流侵蚀作用强烈的前均衡状态时期.塔西河的纵剖面凹曲度最大,向东西两侧河流凹曲度依次降低,乌鲁木齐河与四棵树河凹曲度最小,河流的凹曲度(θ)和河道坡度(Ks)的数值分布规律与所对应构造部位晚更新世以来的抬升速率和地壳缩短速度相一致,排除时间、气候因素和基岩性质影响因素后.发现晚更新世以来天山北麓河流纵剖面形态变化主要受构造抬升作用的影响. 相似文献
2.
庐山是位于江南造山带北缘的断块山,其抬升过程对于认识本区的构造演化至关重要。利用河流纵剖面的形态参数可以定量估算相对的构造抬升速率。基于5 m分辨率的DEM提取了庐山9条主要河流的纵剖面,依据坡度—面积图确定了裂点类型,结合地质图判别出裂点成因,并利用河流水力侵蚀模型计算了稳定态河段的陡峭指数以及凹曲度。结果显示,庐山的河流基本呈过渡态,以发育数量不等的裂点为标志;垂阶型裂点的形成主要与岩石强度不均一有关,而坡断型裂点是侵蚀基准面下降产生的。坡断型裂点以下的基岩河段具有较大的陡峭指数,表明庐山经历了从早期低抬升速率到晚期高抬升速率的转变。庐山受快速抬升影响的河段,陡峭指数具有南高北低的特点,主要是由于庐山整体抬升过程中南部、北部的抬升速率存在一定差异,亦可能是岩性不同造成的。 相似文献
3.
构造地形指标的发展对于构造运动的量化研究具有重要意义。白龙江流域位于青藏高原与西秦岭造山带之间的过渡地带,对该流域地貌是否处于构造隆升与河流侵蚀的均衡状态,以及内部构造活动性的差异如何等问题尚缺乏细致研究。基于Arcgis9.3与ASTERGDEM数据,提取了白龙江流域32条支流的纵剖面,拟合其最佳函数形态,并利用基岩侵蚀模型提取了各个支流的标准化陡峭指数、凹曲度及拟合系数值,来揭示白龙江流域河流对构造运动的响应特征。结果表明:白龙江流域河流拟合函数以指数函数为主,河流大多发育处于侵蚀作用强烈阶段;中上游地区标准化河流陡峭指数值较下游地区偏大,凹曲度值和拟合系数中上游较下游值偏小,反映了白龙江流域中上游与下游构造活动强度的差异性;32条支流的凹曲度大部分小于均衡状态经验平均凹曲度值(0.49),表明白龙江流域地貌形态发育大部分还没有达到均衡阶段。 相似文献
4.
河流裂点形态特征蕴含了区域河流演化的历史信息，是认识区域地貌演化、构造运动、气候变化及人类活动潜在相互作用机制的切入点。以往裂点成因研究多选择在河流演化控制因素比较典型的地区，成因分析方法也相对单一。本文以河流演化环境复杂的大别山东南缘为研究区，基于标准陡峭指数、面积高程积分、坡度-面积双对数法和降水侵蚀力等探讨区域河流裂点形成原因。研究表明：(1)研究区5条河流干流纵剖面均处于不均衡状态，发育68个裂点。(2)研究区裂点发育受到构造活动、岩性、降水等多种因素影响。构造运动特别是郯庐断裂带等的断层活动是区域裂点发育的主导因素，共形成45个裂点，超过裂点总数量的65%。(3)研究区地貌演化受到构造运动影响，区域断层活动显著，并且构造运动活跃性存在差异，山地区域构造运动活跃性高于山前盆地，西南区域构造运动活跃性高于东北区域。本研究可为复杂区域河流演化研究提供借鉴，并从新的视角进一步了解大别山地区地貌演化过程。 相似文献
5.
《地理与地理信息科学》2017,(4)
黄河中游流经黄土高原的核心区域,对黄河中游流域地貌形态特征的定量分析可以反映黄河中游流域地貌演化进程以及黄土高原侵蚀地貌形态特征。该文以黄土高原区域30m分辨率的DEM为信息源,首先提取了黄河中游7条典型一级支流及其纵剖面,然后计算了6种量化指标分析其流域地貌形态以及流域地貌演化进程,在此基础上,构建地貌特征综合评价指标反映黄土高原区域侵蚀地貌形态特征。实验结果表明,秃尾河、无定河以及延河发育至深切侵蚀期;窟野河发育至深切侵蚀和均衡调整之间的过渡期;汾河、洛河以及渭河发育至均衡调整期。流域地貌随河流侵蚀循环而相应演化,7条河流所在流域的地貌发育程度从北到南也基本呈现逐渐成熟的趋势。所计算的侵蚀地貌综合评价指标值显示,窟野河、秃尾河、无定河以及延河流域共同构成黄土高原强烈土壤侵蚀区;汾河、洛河以及渭河流域的土壤侵蚀程度较低。 相似文献
6.
基于遥感技术的黑龙江上中游河道特征研究 总被引：1，自引：0，他引：1
以2000年Landsat-7 ETM+影像、地形图、数字高程数据等为数据源,从河道平面形态及河流纵剖面形态对黑龙江上中游河道特征进行分析。从河流动力特征、流域自然环境条件及人类活动方面探讨其对河道形态特征形成的影响。研究发现:黑龙江上中游河道曲折系数均值为1.20,属于微弯顺直型河道,整体相对稳定,但局部河段河道形态复杂,河流纵剖面形态为下凹型曲线;河流形态的形成遵循一定的河流动力学规律,是水流和河床在自然因素与人类活动影响下相互作用结果。 相似文献
7.
滇西北三江河谷纵剖面的发育图式与演化规律 总被引：12，自引：1，他引：12
在地壳持续、匀速抬升继以长期稳定的构造条件下,均一流域河谷纵剖面形态是以河口或河源为原点的抛物线(h=Al~N)。抬升期,河流深切侵蚀,纵剖面为上凸抛物线型;稳定期,河流均衡调整,纵剖面为下凹抛物线形;其间过渡阶段,纵剖面为直线型。流域地貌随侵蚀循环而相应演化,最终形成准平原。滇西北金沙江、澜沧江、怒江流域接近理想假设条件,其河谷纵剖面的形态和演化符合上述的图式和规律。 相似文献
8.
长江源区河流的河网形态和辫状河型独具特色。基于SRTM3 DEM、Landsat 4-5 TM遥感影像和Google Earth卫星影像数据提取长江源区22条河流纵剖面,利用简单数学函数拟合纵剖面形态,并结合Hack剖面、凹曲指数及河长坡降SL指标等参数分析河流纵剖面的发育与构造活动之间的内在关系。研究表明:长江源区大部分河流纵剖面的最佳拟合形态为指数函数(R~2≥0.99),间接地说明该区域河流侵蚀作用较强。这22条支流的凹度值约为1.0,其中当曲的凹曲度最大,色吾曲最小,属于高凹曲度和极端凹曲度值。在各河流形态的统计结果中,三大源流Hack剖面均为曲线,沱沱河—通天河、当曲、楚玛尔河分别出现了8次、4次、3次宽窄交替的藕节状形态,其中宽谷段为辫状河段,窄段为峡谷限制段,标准河流坡降指数SL/K值介于2～10之间,表示河流发育处于微陡河段,地区构造活动较强。不考虑气候和基岩性质影响因素,可推测晚更新世以来新构造运动在长江源河流纵剖面演变中起主导作用。 相似文献
9.
贺兰山水系流域数值地貌特征及其构造指示意义 总被引：1，自引：1，他引：0
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。 相似文献
10.
为了揭示滇西纵向岭谷区河谷形态特征及其发育规律,采用1∶5万DEM图件,利用ARCG IS软件提取研究区41个河谷断面的有关基础数据,据此计算了河谷横断面的宽深比、半高宽深比、断面面积、凹度、不对称系数及河谷纵剖面特征的指标。结果表明,纵向岭谷区北部河谷横断面的宽深比很小,其宽深比在4~16间,但沿流向往南有明显增大的趋势,最大达到24。这是由于北部的构造抬升作用强从而引起该区更强列的河流下蚀作用的结果。河谷横断面的凹度显示大多数河谷属于"V"型谷,表明研究区的河流仍然以下切过程为主。谷宽不对称系数及谷面不对称系数揭示了研究区河谷横断面主要是左倾型河谷,即河谷断面上河道左部谷坡较缓,这是强势西南季风在河流左岸迎风坡形成强降水带和在河流右岸背风坡形成弱降水带的雨水差异侵蚀引起的。河谷纵剖面具有明显的下凹特性,凹度在1.40~1.65间。河道比降具有沿程变小的趋势,并遵循指数衰减关系,平均比降在1.22‰~1.85‰间。在纵向岭谷区北部,响应构造抬升作用的西强东弱的现状,河流主河道的比降具有从西向东变小的趋势。 相似文献
11.
Model parameterization through adjustment to field data is a crucial step in the modeling and the understanding of the drainage network response to tectonic or climatic perturbations. Using as a test case a data set of 18 knickpoints that materialize the migration of a 0.7-Ma-old erosion wave in the Ourthe catchment of northern Ardennes (western Europe), we explore the impact of various data fitting on the calibration of the stream power model of river incision, from which a simple knickpoint celerity equation is derived. Our results show that statistical least squares adjustments (or misfit functions) based either on the stream-wise distances between observed and modeled knickpoint positions at time t or on differences between observed and modeled time at the actual knickpoint locations yield significantly different values for the m and K parameters of the model. As there is no physical reason to prefer one of these approaches, an intermediate least-rectangles adjustment might at first glance appear as the best compromise. However, the statistics of the analysis of 200 sets of synthetic knickpoints generated in the Ourthe catchment indicate that the time-based adjustment is the most capable of getting close to the true parameter values. Moreover, this fitting method leads in all cases to an m value lower than that obtained from the classical distance adjustment (for example, 0.75 against 0.86 for the real case of the Ourthe catchment), corresponding to an increase in the non-linear character of the dependence of knickpoint celerity on discharge. 相似文献
12.
《Geomorphology》2006,73(1-2):16-32
Well-constrained case studies of transient landscape response to external forcing are needed to improve our understanding of erosion processes in tectonically active mountain belts. The Peninsular Ranges portion of the San Jacinto fault zone (SJFZ) is an excellent location for such a study because it displays pronounced geomorphic disequilibrium resulting from initiation of a major strike-slip fault in the past 1.0 to 2.5 million years. We recognize two geomorphic domains in this region: (1) a relict low-relief upland domain consisting of broad flat valleys and low-gradient streams and (2) very steep, rough topography with deeply incised canyons and retreating erosional knickpoints. Pleistocene sediments exposed along and near the SJFZ include fluvial conglomerate, sandstone, and mudstone, with weak paleosols and west- to NW-directed paleocurrents. These sediments accumulated in a low-gradient stream system (represented by domain 1) during an early phase of slip in the SJFZ, prior to the modern phase of erosion and degradation (domain 2). Late Pliocene or early Pleistocene initiation of the SJFZ triggered a wave of headward erosion and stream capture that is still migrating NW along the fault zone. Using the total distance that capture points have migrated along the fault zone and a range of possible ages for fault initiation, the rate of knickpoint retreat is estimated at ∼ 12 to 44 km/my.To explore the signal of transient geomorphic response to fault initiation, we analyzed 23 tributaries along an ∼ 20-km portion of the main fault valley within domain 2. The analysis reveals three zones with distinctive morphologies: (1) strongly convex longitudinal profiles in the NW, (2) a large (ca. 5–6 km2) landslide in the central zone, and (3) concave tributaries in the SE with profile complexity decreasing and catchment area increasing from NW to SE. The distribution of these zones suggests close spatial and temporal association of active fault slip, bedrock incision, deep-seated landslides, and erosional modification. The fundamental driving force behind these processes is profound geomorphic disequilibrium resulting from initiation of the SJFZ. We suggest that landslides may have played a significant role in shaping the morphology of this fault zone, and that the influence of landslides may be underestimated in areas where characteristic landforms and deposits are obscured by later erosion and faulting. 相似文献
13.
The kinematics and pattern of escarpment retreat across the rifted continental margin of SE Australia 总被引：2，自引：1，他引：2
Rifted continental margins generally display an interior, low-relief, highly weathered upland area and a deeply incised, high-relief coastal area. The boundary between the two zones is commonly demarcated by an abrupt, seaward-facing escarpment. We investigate the rate and pattern of escarpment erosion and landscape evolution along the passive margin of south-east Australia, in the region of the New England Tableland. The process of rifting is shown to initiate an escarpment across which rivers flow, resulting in an escarpment that takes the form of dramatic, elongated gorges. Using a mass balance approach, we estimate the volume/unit length of continental material eroded seaward of the escarpment to be between 41 and 68 km2 , approximately an order of magnitude less than the 339 km2 of terrigenous sediments calculated to have been deposited offshore, but consistent with earlier denudation estimates based on apatite fission track data. On the bedrock rivers draining the New England Tableland region, the escarpment is manifested as a series of sharp knickpoints punctuating the river longitudinal profiles. The knickpoints are situated the same distance upstream along the different channels and uniform escarpment retreat rates on the order of 2 km Myr−1 are estimated, despite some differences in bedrock lithologies. Gorge head migration appears to be very important as a bedrock incision mechanism. Field observations indicate a coupling between escarpment retreat and knickpoint propagation, bedrock channel incision, and hillslope development. 相似文献
14.
Rivers respond to a drop in their base level by incising the topography. The upstream propagation of an incision, as usually depicted by a knickpoint migration, is thought to depend on several parameters such as the drainage area, lithology, and the amplitude of the base level drop. We first investigate the case of the Messinian Salinity Crisis that was characterized by the extreme base level fall (1500 m) of the Mediterranean Sea at the end of the Miocene. The response of drainage areas of three orders of magnitude (103 to 106 km2) highlights the dominant role of the drainage area (with a square root relationship) in controlling the knickpoint migration after a base level fall. A compilation of mean rates of knickpoint propagation for time durations ranging from 102 to 107 years displays a similar relationship indicating that successive wave trains of knickpoint can migrate in a river: first, wave trains linked to the release of the alluvial cover and then, wave trains related to the bedrock incision, which correspond to the real time response of rivers. Wave trains with very low retreat rates (long lived knickpoints > 1 My) rather correspond to the response time of regional landscape. 相似文献
15.
The Argentera Massif (French–Italian Alps), with its uniform lithology, was selected to evaluate how known Plio–Pleistocene tectonics have conditioned the drainage network geometry. The drainage network was automatically derived and ordered from a 10 m-resolution DEM. On hillshade images, alignments of morphological features were identified. The Massif was subdivided into 22 domains of 50 km2 within which the directions of every river channel segment and the direction of the aligned morphological features were compared and contrasted with the strike of tectonic structures measured in the field. Results suggest that the Argentera drainage system is variously controlled by recent tectonics, depending on the Massif sector taken into account. In the NW sector, the vertical uplift is less because the strain has been accommodated in an oblique direction along a lateral thrust. In the SE sector, strain in a predominantly vertical direction along a frontal thrust has resulted in a major vertical displacement. Accordingly, the NW sector is characterized by (i) a strong geometric relationship between the main tectonic structures and the directions of river channels, (ii) longitudinal main rivers bordering the Massif, and (iii) a general trellis pattern within the domains.In the SE sector, the prolonged uplift has forced an original longitudinal drainage system to develop as a transverse system. This change has occurred by means of fluvial captures that have been identified by the presence of windgaps, fluvial elbows and knickpoints. At the domain scale, intense uplift of the SE sector has prompted the drainage pattern to evolve as a dendritic type with no clear influence of structure in the channel orientations. 相似文献
16.
Yuichi S. Hayakawa Takashi Oguchi 《Geografiska Annaler: Series A, Physical Geography》2014,96(1):9-19
Knickzones, defined here as locally steep reaches including distinct knickpoints, in bedrock river morphology, have often been investigated in relation to local anomalies in lithology, tectonics, hydraulics, climate and associated base‐level change, and/or deformation of valley‐side slopes. However, exact formative causes of many knickzones in a humid, tectonically active island arc remain unclear. Using databases of geology, streams and knickzones, we examine knickzone distribution across the Japanese Archipelago to evaluate the effects of the stream network structure and rock type boundaries on knickzone formation. Knickzones are frequently found just upstream and downstream of major stream confluences along mainstreams, whereas knickzones are less frequent around major rock type boundaries. While the major confluences do not form hanging valleys due to similar catchment size, this observation suggests that many knickzones have been formed by the long‐term effect of flow turbulence scouring bedrock at the confluences. Such a hydraulic control on bedrock erosion in the steep Japanese mountains under humid climate conditions indicates that the formative cause of many knickzones therein can be autogenic by means of stream hydraulics. 相似文献
17.
中国蓼科花粉类型的地理分布格局及其与生态因子的关系 总被引：2，自引：2，他引：0
从蓼科植物的孢粉类型角度,研究了中国蓼科花粉类型的地理分布格局及其与生态因子的关系。根据中国蓼科植物赖以生存的生态因子,得出中国蓼科花粉类型分布区的主要生态因子,包括地理位置(分布中心)、海拔高度、年降水量、年积温及生境数量。在此基础上,根据同一区域内相同或相似的生态环境条件下分布的现代蓼科各种花粉类型,确定一定花粉类型组合所指示的现代气候和环境,为利用地层中蓼科化石花粉重建古气候、古环境及气候变迁提供了现代孢粉学证据。 相似文献
18.
杨逸畴 《云南地理环境研究》1999,11(2):1-8
分析了大峡谷的基本特点, 把它看作是内外作用营力的现阶段表现。提出了内营力的地质基础是破碎的、不良的、不稳定的; 外营力的水汽通道带来强大水热作用的负面影响, 它们结合在一起, 组成了生态环境本质极为脆弱的基础。并把历史上的重大山地灾害当作是一面镜子; 而把现实看到的破坏作为人类参与下正在长鸣的警钟, 提醒人们要建立大峡谷生态环境是极为脆弱的基本概念, 一切要以环保为基础, 以可持续发展为根本目标。 相似文献
19.
Treelines are widely studied worldwide in relation to climate changes because they are hypothesized to be sensitive climate proxies. However, forest treeline expansion toward higher altitudes may be influenced both by a warming climate and by other factors, such as surface morphology and, in the European Alps, the decline in alpine farming. Our results from five valleys in the inner and peripheral regions of the Alps show that present-day treeline altitudes mostly depend on anthropogenic and orographicgeomorphologic factors. Climatic treelines are limited to steep and inaccessible slopes, and occur at higher altitudes and farther from mountain peaks in the inner regions than in the peripheral regions of the mountain range. Looking for sites in which to study treeline responses to climate change, we recommend investigating the inner regions of the Alps where treelines are farther from human disturbances and from geomorphologic constraints, potentially resulting in freer upward shifts under warmer temperature conditions. We also found that, in the valleys selected, human disturbance is mainly concentrated about 165 m below non-climatic treelines, suggesting a homogeneous influence on treelines, regardless of geographic position. 相似文献