Wood storage in a wide mountain river: case study of the Czarny Dunajec,Polish Carpathians     

Bart&#x;omiej Wyga  Joanna Zawiejska 《地球表面变化过程与地形》2005,30(12):1475-1494

Storage of large woody debris in the wide, mountain, Czarny Dunajec River, southern Poland, was investigated following two floods of June and July 2001 with a seven‐year frequency. Within a reach, to which wood was delivered only by bank erosion and transport from upstream, wood quantities were estimated for eighty‐nine, 100 m long, channel segments grouped into nine sections of similar morphology. Results from regression analysis indicated the quantity of stored wood to be directly related to the length of eroded, wooded banks and river width, and inversely related to unit stream power at the flood peak. The largest quantities of wood (up to 33 t ha^?1) were stored in wide, multi‐thread river sections. Here, the relatively low transporting ability of the river facilitated deposition of transported wood while a considerable length of eroded channel and island banks resulted in a large number of trees delivered from the local riparian forest. In these sections, a few morphological and ecological situations led to the accumulation of especially large quantities of wood within a small river area. Very low amounts of wood were stored in narrow, single‐thread sections of regulated or bedrock channel. High stream power facilitated transport of wood through these sections while the high strength of the banks and low channel sinuosity prevented bank retreat and delivery of trees to the channel. Considerable differences in the character of deposited wood existed between wide, multi‐thread channel sections located at different distances below a narrow, 7 km long, channellized reach of the river. Wood deposited close to the downstream end of the channellized reach was highly disintegrated and structured into jams, whereas further downstream well preserved shrubs and trees prevailed. This apparently reflects differences in the distance of wood transport and shows that in a mountain river wider than the height of trees growing on its banks, wood can be transported long distances along relatively narrow, single‐thread reaches but is preferentially deposited in wide, multi‐thread reaches. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

泥石流运动衰减动力学初步研究     

陈洪凯唐红梅  吴四飞 《中国地质灾害与防治学报》2005,16(B12):56-61

我国公路泥石流病害严重，泥石流淤埋公路构建筑物是一类常见的公路泥石流病害类型。泥石流衰减动力学是防治泥石流淤埋病害的重要关键技术，也是泥石流运动学、动力学研究的核心问题之一。本文作者运用泥沙运动力学及流体力学原理，初步建立了泥石流固相颗粒和液相浆体的能量衰减条件，把泥石流衰减模式概化为两类，即能量抑制衰减和能量自由衰减；通过泥石流沉积模型试验，得到了不同粘度泥石流体的沉积扇变化形态，随着泥石流体粘度的增大，沉积扇边缘变陡、扩展范围变小、纵轴线长度减小等结论与实际情况吻合；初步建立了泥石流能量衰减速率计算方法。研究成果为防治公路泥石流病害奠定了基础。  相似文献   

A climatic trigger for catastrophic Pleistocene–Holocene debris flows in the Eastern Andean Cordillera of Colombia          下载免费PDF全文

N. HOYOS  O. MONSALVE  J. L. ANTINAO  H. GIRALDO  C. SILVA  G. OJEDA  G. BAYONA  J. ESCOBAR  C. MONTES 《第四纪科学杂志》2015,30(3):258-270

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Quaternary evolution of the northern North Sea margin through glacigenic debris‐flow and contourite deposition     

《第四纪科学杂志》2017,32(3):416-426

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Developing millennial tree ring chronologies in the fire‐prone North American boreal forest     

DOMINIQUE ARSENEAULT  BENJAMIN DY  FABIO GENNARETTI  JULIA AUTIN  YVES BÉGIN 《第四纪科学杂志》2013,28(3):283-292

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Autogenic avulsion,channelization and backfilling dynamics of debris‐flow fans          下载免费PDF全文

Tjalling de Haas  Wilco van den Berg  Lisanne Braat  Maarten G. Kleinhans 《Sedimentology》2016,63(6):1596-1619

Alluvial fans develop their semi‐conical shape by quasi‐cyclic avulsions of their geomorphologically active sector from a fixed fan apex. On debris‐flow fans, these quasi‐cyclic avulsions are poorly understood, partly because physical scale experiments on the formation of fans have been limited largely to turbidite and fluvial fans and deltas. In this study, debris‐flow fans were experimentally created under constant extrinsic forcing, and autogenic sequences of backfilling, avulsion and channelization were observed. Backfilling, avulsion and channelization were gradual processes that required multiple successive debris‐flow events. Debris flows avulsed along preferential flow paths given by the balance between steepest descent and flow inertia. In the channelization phase, debris flows became progressively longer and narrower because momentum increasingly focused on the flow front as flow narrowed, resulting in longer run‐out and deeper channels. Backfilling commenced when debris flows reached their maximum possible length and channel depth, as defined by channel slope and debris‐flow volume and composition, after which they progressively shortened and widened until the entire channel was filled and avulsion was initiated. The terminus of deposition moved upstream because the frontal lobe deposits of previous debris flows created a low‐gradient zone forcing deposition. Consequently, the next debris flow was shorter which led to more in‐channel sedimentation, causing more overbank flow in the next debris flow and resulting in reduced momentum to the flow front and shorter runout. This topographic feedback is similar to the interaction between flow and mouth bars forcing backfilling and transitions from channelized to sheet flow in turbidite and fluvial fans and deltas. Debris‐flow avulsion cycles are governed by the same large‐scale topographic compensation that drives avulsion cycles on fluvial and turbidite fans, although the detailed processes are unique to debris‐flow fans. This novel result provides a basis for modelling of debris‐flow fans with applications in hazards and stratigraphy.  相似文献   

Coupled Model of Two-phase Debris Flow, Sediment Transport and Morphological Evolution     

HE Siming  OUYANG Chaojun  LIU Wei  WANG Dongpo 《《地质学报》英文版》2016,90(6):2206-2215

The volume fraction of the solid and liquid phase of debris flows,which evolves simultaneously across terrains,largely determines the dynamic property of debris flows. The entrainment process significantly influences the amplitude of the volume fraction. In this paper,we present a depth-averaged two-phase debris-flow model describing the simultaneous evolution of the phase velocity and depth,the solid and fluid volume fractions and the bed morphological evolution. The model employs the Mohr–Coulomb plasticity for the solid stress,and the fluid stress is modeled as a Newtonian viscous stress. The interfacial momentum transfer includes viscous drag and buoyancy. A new extended entrainment rate formula that satisfies the boundary momentum jump condition(Iverson and Ouyang,2015) is presented. In this formula,the basal traction stress is a function of the solid volume fraction and can take advantage of both the Coulomb and velocity-dependent friction models. A finite volume method using Roe's Riemann approximation is suggested to solve the equations. Three computational cases are conducted and compared with experiments or previous results. The results show that the current computational model and framework are robust and suitable for capturing the characteristics of debris flows.  相似文献   

北京山区泥石流预警阈值初步研究   总被引：1，自引：0，他引：1  

贾三满  路璐  翟淑花  王海芝  王珊珊  齐干 《城市地质》2016,(3):1-7

泥石流预警阈值,是突发地质灾害防灾减灾的重要参考指标。本文结合北京山区泥石流灾害特点和已有降雨阈值研究成果,一方面在泥石流沟易发性、物源和危害人数进行分级的基础上,提出不同级别沟谷在不同前期降雨条件下,不同发灾概率的激发雨量,极大地方便了中短期预警实际工作;另一方面将泥石流流域降雨量、土壤含水率、次声、泥位4个参数,作为泥石流短临灾害预警关键物理参数,开展了泥石流专业监测设备预警阈值研究。最终,从技术层面上构建不同时间维度的泥石流监测预警阈值体系,为北京山区泥石流监测预警提供技术支持。  相似文献   

Snow disaster characteristics in Palongzangbu River Basin and mitigation countermeasures for road engineering     

ShuSu Duan  LingKan Yao  XiaoDan Sun  Qiang Cai 《寒旱区科学》2016,8(2):95-102

The Palongzangbu River Basin contains the highest number of maritime province glaciers in China.There are 130 glacial lakes,64 snow avalanche sites and 28 glacial debris flow gullies distributed within the basin.Snow disasters play a controlling role in the Sichuan-Tibet Highway construction,due to the terrain's special characteristics of high altitude and large height differential.Segmentation mitigation countermeasures for the Sichuan-Tibet Highway are presented based on snow disaster severity level and damage mode of the road.In the Ranwu to Midui section,snow avalanches are regional disasters, so the line should be placed in sunny slopes.In the Midui Gully to Yupu section,the line should be placed in shady slopes and at higher elevations to reduce the risk of glacial lake outburst.In the Yupu to Guxiang section,all three snow disasters are minimal.In the Guxiang to Tongmai section,glacier debris flows are the major threat,thus the road should be placed in shady slopes.  相似文献   

Protection of marine birds and turtles at St Brandon’s Rock,Indian Ocean,requires conservation of the entire atoll     

SW Evans  N Cole  H Kylin  NS Choong Kwet Yive  V Tatayah  J Merven 《African Journal of Marine Science》2016,38(3):317-327

A survey of seabirds and turtles at St Brandon’s Rock, 400 km north of Mauritius, was undertaken in 2010. We estimated that 1 084 191 seabirds comprising seven breeding species and excluding non-breeders were present at the archipelago and we counted 279 turtle tracks and nesting pits of green turtles Chelonia mydas. Hawksbill turtles Eretmochelys imbricata were also present. Analyses of 30 different islets that make up the atoll showed that the seabird species mostly partitioned their use of islets based on islet size, with four species preferring larger islets and two species preferring smaller islets. Alien species introduced historically are still present and other threats, such as shipwrecks, remain. We propose conservation and other measures that should adequately protect the birds, turtles and coral reef by treating the atoll as a system.  相似文献