Historical analysis indicates seepage control on initiation of meandering     

J. P. C. Eekhout  A. J. F. Hoitink  B. Makaske 《地球表面变化过程与地形》2013,38(8):888-897

In analytical and numerical models of river meandering, initiation of meandering typically occurs uniformly along the streamwise coordinate in the channel. Based on a historical analysis of the Nierskanaal, here we show how and under which circumstances meandering has initiated in isolated sections of a channel. The Nierskanaal was constructed by the end of the 18th century, as a straight channel between the river Niers and the river Meuse. The purpose of this measure was to reduce flood risk in the downstream reaches of the river Niers. The banks on the Dutch part of the channel were left unprotected and developed into a morphodynamically active channel, featuring a meandering planform and valley incision. The planform development and incision process is analysed using topographic maps and airborne LiDAR data. Meandering initiated in three sections of the channel, where the channel sinuosity developed asynchronously. Sedimentary successions in the study area show layers of iron oxide, indicating groundwater seepage from aeolian river dunes and river deposits located nearby. Only at the spots where meandering has initiated iron oxide is found close to the surface level. This provides a clue that seepage triggered bank erosion by increasing moisture content of the banks. The isolated meandering sections expanded in the longitudinal direction. Valley incision has developed in the first decades after the construction of the channel, and diminished after a gravel layer was reached. Gravel was deposited in the downstream half of the channel bed, acting as an armouring layer. The spatial variation in meandering behaviour, as observed in the Nierskanaal, justifies efforts to implement the influence of floodplain heterogeneity and the effect of seepage on bank erosion in meander models. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Self-organizing maps for multi-scale morphometric feature identification using shuttle radar topography mission data     

Amir Houshang Ehsani  Friedrich Quiel 《国际地球制图》2013,28(5):335-355

  相似文献   

Sediment Transport in a Proglacial Valley,Sermilik, East Greenland     

Bent Hasholt M.Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):105-110

Hasholt, Bent: Sediment Transport in a Proglacial Valley, Sermilik, East Greenland, Geografisk Tidsskrift 92:105–110, Copenhagen 1992.

Detailed investigations of sediment transport have been carried out in a proglacial valley at the Mitdluagkat Glacier in East Greenland. The results from 1989, 1990 and 1991 have been compared with earlier measurements of sediment transport. The hydrologie regime will be described and the effect of the development of an icing on the fluvial transport will be discussed.  相似文献   

ISSUES CONFRONTING GEOGRAPHIC EDUCATORS IN EUROPE AND THE U.S.S.R.     

《The Professional geographer》2013,65(4):379-385

Bedrock forms of etch origin result from the interaction of groundwaters and bedrock at the weathering front at the base of the regolith. They are significant for general theories of landscape and landform genesis because they are azonal with respect both to climate and lithology. Two stages of etch form development are recognized: one involves weathering and the formation of a regolith; the second consists of stripping of the regolith and the exposure of the bedrock forms. Although etch forms have been recognized for some two centuries, the concept of etching as a process of landform development has been neglected, particularly in North America.  相似文献   

Character,Age, and Ecological Significance of Pleistocene Periglacial Slope Deposits in Germany   总被引：1，自引：1，他引：0  

《自然地理学》2013,34(6):451-473

Periglacial slope deposits (PSD) of Pleistocene age are one of the most widely distributed sediment types in nonglaciated mid-latitude regions. As diamictons of different genesis (geli-solifluction, cryoturbation, eolian transportation) they have a wide range of physical, chemical and mineralogical characteristics which are mainly controlled by bedrock geology, including saprolite. This paper reviews concepts used in Germany to study PSD stratigraphy and describes the different PSD units encountered (Upper Head, Middle Head, Lower Head). The paper is relevant to the understanding of PSDs in other mid-latitude regions. Classical and new results concerning the age of PSDs show differences in the interpretation of Upper Head genesis. In terms of their ecological significance, case studies from eastern Bavaria illustrate the influence of PSDs on the character and intensity of slope hydrological processes as well as on the formation and distribution of soils. Presently important research questions include (1) the establishment of a genetically based classification of PSDs, (2) the intensification of dating studies on PSDs, and (3) the clarification of hydrological processes in PSDs.  相似文献   

Fluvial diversity in relation to valley setting in the source region of the Yangtze and Yellow Rivers   总被引：3，自引：3，他引：0  

Guo-an Yu  Le Liu  Zhiwei Li  Yanfu Li  Heqing Huang  Gary Brierley  Brendon Blue  Zhaoyin Wang  Baozhu Pan 《地理学报(英文版)》2013,23(5):817-832

The spatial distribution of valley setting （laterally-unconfined, partly-confined, or confined） and fluvial morphology in the source region of the Yangtze and Yellow Rivers is contrasted and analyzed. The source region of the Yangtze River is divided into 3 broad sections （I, II and III） based on valley setting and channel gradient, with the upstream and downstream sections being characterized by confined （some reaches partly-confined） valleys while the middle section is characterized with wide and shallow, laterally-unconfined valleys. Gorges are prominent in sections I and III, while braided channel patterns dominate section II. By contrast, the source region of the Yellow River is divided into 5 broad sections （sections I-V） based on valley characteristics and channel gradient. Sections I, II and IV are alluvial reaches with mainly laterally-unconfined （some short reaches partly-confined） valleys. Sections III and V are mainly confined or partly-confined. Greater morphological diversity is evident in the source region of the Yellow River relative to the upper Yangtze River. This includes braided, anabranching, anastomosing, meandering and straight alluvial patterns, with gorges in confined reaches. The macro-relief （elevation, gradient, aspect, valley alignment and confinement） of the region, linked directly to tectonic movement of the Qinghai-Tibet Plateau, tied to climatic, hydrologic and biotic considerations, are primary controls upon the patterns of river diversity in the region.  相似文献   

河南伊洛河流域更新世地貌演变及驱动评述     

邱士可  鲁鹏 《地理与地理信息科学》2013,29(3)

根据野外调查,结合相关文献,利用GIS制图与空间分析功能对伊洛河流域更新世地貌特征与演化进行了分析,在原有地貌类型基础上划分若干地貌单元,对各类地貌单元的海拔高度、坡度、面积及比例进行量算,并对地貌演变的气候与构造驱动进行评述,为区域早期人地关系研究奠定基础.结果显示,晚第三纪以来发生的新构造运动,在区域主要表现为间歇性的抬升,其对区域宏观地貌特征的形成起到决定作用.新近纪以来的气候冷、暖、干、湿的交替波动,在地貌发育过程中起到较小尺度下的修塑作用,主要表现为堆积、侵蚀等不同特征.伊洛河流域现代地貌特征的形成是构造、气候等因素共同作用的结果.尽管燕山运动奠定了伊洛河流域的地貌轮廓,但在内外力共同作用下,区域地貌不断演变,现代地貌特征逐步形成且仍在不断演化之中.  相似文献   

Rapid flooding of the southern Vietnam shelf during the early to mid‐Holocene          下载免费PDF全文

RIK TJALLINGII  KARL STATTEGGER  PAOLO STOCCHI  YOSHIKI SAITO  ANDREAS WETZEL 《第四纪科学杂志》2014,29(6):581-588

  相似文献   

2007年7月江淮流域降水过程云分辨尺度模拟研究Ⅱ——降水过程模拟诊断   总被引：1，自引：0，他引：1  

许凤雯  崔晓鹏  许小峰  刘文明  王志 《热带气象学报》2011,27(3):365-364

本系列工作上一篇文章利用美国Goddard中心的云分辨尺度模式,对2007年7月2-9日发生在我国江淮流域的暴雨过程开展了较成功的云尺度数值模拟,并利用地面降水以及雷达等观测资料对模拟结果进行了验证.指出,模式较好地模拟出了强降水过程的时空分布和演变特征等.在此基础上,利用地而降水诊断方程,结合上述高分辨率的强降水过程...  相似文献   

张家界砂岩地貌形成时代:来自阶地与溶洞对比的证据   总被引：2，自引：0，他引：2       下载免费PDF全文

平亚敏  杨桂芳  张绪教  田明中  陈安泽  葛之亮  倪志云  杨振 《地质论评》2011,57(1):118-124

张家界以其独特罕见的石英砂岩峰林地貌闻名于世,一直是地貌学家、地质学家们关注的焦点,但关于其形成年代问题尚显薄弱,一直缺乏系统深入的研究.本文对索溪流域不同层状地貌进行了地貌学、沉积学和年代学综合研究.研究结果表明,索溪河谷普遍发育三级阶地,T;很少发育,主要表现为河流两侧化置较高的古宽谷或剥蚀面.岩溶洞穴黄龙洞从上往...  相似文献