Estimating the size and travel distance of Klapperhorn Mountain debris flows for risk analysis along railway, Canada

Debris flows occurring on Klapperhorn Mountain in the Yellowhead Pass in the Canadian Rocky Mountains pose a significant hazard to railway operations at the base of the mountain. The size （volume） and travel distance of these debris flows play an important role in assessing the risk to the railway. GIS analysis, airphoto interpretation together with field work were undertaken on two debris flows located at track mileage 54.0 and 54.3. Characteristics of these two debris flow events were analyzed, including debris flow path morphology and event behavior. Their sizes and travel distances were estimated using an empirical-statistical model （UBCDFLOW） under different initiation conditions. Their potential impact on the railway bridge was evaluated using a bridge blockage ratio.     

Lichenometric dating of debris-flow deposits in the Scottish Highlands

Debris-flow deposits, dated by lichenometry, indicate that the majority of hillslope debris flows in Scotland have occurred within the last 500 years. Progressive weathering and climatic change can be discounted as the prime cause of the increase in the incidence of debris flows. The timing of the increase suggests that it is related to landuse changes in the Scottish Highlands during the 19th and early 20th centuries. Both burning and overgrazing can be cited as potential causal factors.     

Testing the use of OSL from quartz grains for dating debris flows in Miyun,northeast Beijing,China

Extreme seasonal summer rain storms are common in the mountains to the north east of Beijing and these often result in mass movement of sediment slurries transported for up to a few km. These debris flows can be deadly and are very destructive to infrastructure and agriculture. This project tests the application of luminescence dating to determining the return frequency of such extreme events. The high sediment concentration and the very short flow duration gives very little opportunity for daylight resetting during transport and only a small fraction of the total mass is likely to be reset before transport begins. Here we examine the quartz single-grain dose distribution from a recent known-age (<25 years) debris flow from a small (∼3.9 km²) catchment ∼140 km north of Beijing and compare it with those from three samples from a sedimentary sequence containing the evidence of multiple flow events.Multi-grain quartz OSL signals are dominated by the fast component and <1% of the 150–200 μm grains give a detectable test dose (4.5 Gy) response. Single-grain beta dose recovery gave a ratio of 0.97 ± 0.06 (n = 30) with an over-dispersion of 23 ± 8% (CAM). Both the recent known age and the palaeo-distributions are highly dispersed with over-dispersions greater than 50%. The average weighted doses range between ∼3 mGy and ∼6.5 Gy, indicating that all deposits are no more than a few thousand years. Minimum age modelling give an age estimate for the youngest sample consistent with the known age, and minimum ages for the older palaeo-deposits suggest that there have been at least 3 major debris flows in this small catchment in the last 1000 years.     

Closure relations for mobile bed debris flows in a wide range of slopes and concentrations

Debris flows are flows of water and sediment driven by gravity that initiate in the upper part of a stream, where the slope is very steep, allowing high values of solid concentration (hyperconcentrated flows), and that stop in the lower part of the basin, which is characterized by much lower slopes and reduced speeds and concentrations. Modelling these flows requires mathematical and numerical tools capable of simulating the behavior of a fluid in a wide range of concentrations of the solid phase, spanning from hyperconcentrated flows to flows in the fluvial regime. According to a two-phase approach, the depth integrated equations of mass and momentum conservation for water and sediments, under the shallow water hypothesis, are employed to solve field problems related to debris flows. These equations require suitable closure relations that in this case should be valid in a very wide range of slopes. In the hypothesis of absence of cohesive material, we derived these closure relations properly combining the relative relations valid separately in the fluvial and in the hyperconcentrated regimes. In the intermediate regime, the shear stress is due to the combined effect of the deformation of the liquid phase (grain roughness turbulence) and of inter-particle collisions. Therefore, an approach based on the sum of the effects of the two causes has been proposed, combining the Darcy–Weisbach equation and the Bagnoldian grain-inertia theory.A similar treatment has been made for the transport capacity relations, combing the Bagnold expression of the collisional regime with a transport capacity monomial formula valid in the fluvial regime.The closure relations are expressed in non-dimensional form as a function of the Froude number, of the solid concentration, of the relative submergence, and of the slope.In order to test the closure relation, a set of experiments with mixtures of non-cohesive sediments and water have been carried out in a laboratory flume under steady uniform flow conditions, with different solid and liquid discharges and different grain size distributions. The closure equations are satisfactorily tested against experimental investigation.     

Possible effect of ENSO on annual sediment discharge of debris flows in the Jiangjia Ravine based on Morlet wavelet transforms

The multi-time-scale structures of an annual sediment discharge series of debris flow in the Jiangjia Ravine and the Southern Oscillation index are analysed using the method of Morlet wavelet transformations. The possible effects of E1 Nirio episodes on the annual sediment discharge are discussed by comparing the period variations of ENSO and the discharge. The results show that the annual sediment discharge series of debris flow is related to E1 Nifio episodes. Generally, the annual sediment discharge of debris flow is less than usual during an E1 Nifio episode and debris flow is less active. On the contrary, the annual sediment discharge of debris flows is greater than usual during a La Nifia episode and debris flows are more frequent. There is a relationship between the annual sediment discharges of debris flow in the Jiangjia Ravine and the summer Southern Oscillation index, with both having quasi-periodic variations of 2 and 5-6 years.     

Determination of the suspension competence of debris flows based on particle size analysis

The determination of the critical particle size between solid and fluid phases, i.e., the suspension competence, is fundamental for debris flow. A method for determining suspension competence based on particle size analysis is presented in this paper. Suspension competence of static experimental water-debris mixtures prepared with the sediment of Jiangjia Gully is -0.025 mm if the bulk density is less than 1,800 kg m-3 and it increases with bulk density of more concentrated mixtures. Suspension competence of natural debris flows in Jiangjia Gully increases exponentially with the bulk density. These two data sets are compared in order to understand the suspension mechanism. It is concluded that turbulence may play a leading role in particle suspension in non-viscous and sub-viscous debris flows, while in viscous debris flows both matrix strength and excess pore water pressure play important roles.     

北京地区泥石流灾害的发育特征及预报方法探讨

通过认真研究北京地区泥石流的发育特征,深入分析了泥石流的形成条件和影响因素,并在此基础上对北京地区泥石流预报方法进行了初步探讨．建立了综合考虑地形地貌、地质条件、土壤类型以及降雨情况等因素的判断公式,并就北京地区泥石流预报方法提出了建议。     

鹅掌河泥石流对四川邛海影响的初步研究

沉积作用在湖泊的演化和消亡过程中至关重要,洪水泥石流的淤积作用对我国西南地区广泛分布的构造断陷湖泊是一个普遍的环境问题．通过调查鹅掌河泥石流发育背景,人类的活动对泥沙进入邛海的影响和对比1988年与2003 年邛海水下地形图得出:在近30年的时间内,鹅掌河洪水和泥石流改沿固定河堤流入邛海,在湖底形成浊流,将更大量泥沙带到湖中．浊流在鹅掌河河口的水下扇陡坡上形成一水下冲沟,在湖底沉积区形成一条长2 km的水下堤．计算发现, 鹅掌河泥石流带入邛海的泥沙远大于一般土壤侵蚀产沙量,其中以1996,1997和1998三年泥石流输入的泥沙量最多．鹅掌河洪水和泥石流对邛海的影响以及水下地形、湖泊基本特征和湖泊环境的变化,应引起人们对邛海保护的高度关注．     

The influence of debris flows on channels and valley floors in the Oregon Coast Range,U.S.A.

Debris flows are one of the most important processes which influence the morphology of channels and valley floors in the Oregon Coast Range. Debris flows that initiate in bedrock hollows at heads of first-order basins erode the long-accumulated sediment and organic debris from the floors of headwater, first- and second-order channels. This material is deposited on valley floors in the form of fans, levees, and terraces. In channels, deposits of debris flows control the distribution of boulders. The stochastic nature of sediment supply to alluvial channels by debris flows promotes cycling between channel aggradation which results in a gravel-bed morphology, and channel degradation which results in a mixed bedrock- and boulder-bed morphology. Temporal and spatial variability of channel-bed morphology is expected in other landscapes where debris flows are an important process.     

Mass flows and river response in rapid uplifting regions – A case of lower Yarlung Tsangpo basin,southeast Tibet,China

The fluvial geomorphology in tectonically active (particularly rapid uplift) regions often undergoes continuous change. The rapid uplift is coincident with high erosion rates; consequently, incised valleys are formed. Mass flows (for example, avalanches, landslides, and debris flows) in incised valleys can markedly influence fluvial processes and even reshape valley geomorphology. However, these processes and long-term evolution corresponding to mass flows require further clarification. Field campaigns were carried out in the region near the Yigong Tsangpo and Palong Tsangpo Rivers (hereafter the Yigong and Palong Rivers), the two largest tributaries of the lower Yarlung Tsangpo River, to examine the feedback between fluvial processes and mass flows. Remote sensing images from recent decades were used to compare the channel morphology before and after typical mass flows (particularly catastrophic ones). The morphology of the lower Yigong River has evidently been impacted by landslides, while that of the Palong River has mainly been shaped by glacial processes and debris flows. At present, the morphology of the latter consists of alternating sections of gorges and wide valleys, with a staircase-like longitudinal profile. The gorge sections exhibit single and deeply incised channels with a high-gradient channel bed and terraces. In contrast, the wide valley sections consist of lakes, braided or anabranching channels, gentle bed gradients, and thick alluvial deposits. Debris flows occur more frequently in gullies in the reaches of the gorge sections and rarely in gullies along the wide valley sections. The occurrence of mass flow events has resulted in an imbalance of the previous (quasi-)equilibrium in the river morphology; however, this has triggered negative feedback that is driving the transient river morphology to a new state of (quasi-)equilibrium.     

西藏天摩沟冰川遥感监测及泥石流触发成因分析

对于有冰川发育的泥石流隐患点而言, 获取冰川动态有助于分析泥石流触发成因.西藏波密县天摩沟是大型泥石流灾害隐患点, 在过去二十年中多次暴发泥石流.本文利用Planet、TanDEM-X和Sentinel-2卫星数据估计了天摩沟冰川2016—2021年间的边界变化、2000—2016年间的表面高程变化, 以及2016—2021年间的流速变化.冰川边界、表面高程和流速变化观测结果均表明天摩沟冰川在2018年7月11日大型泥石流暴发前未发生跃动或崩塌.通过分析高分辨光学影像和气象数据, 认为冰川附近山体崩滑产生的岩屑, 冰川前方的冰碛物和散冰, 以及主沟中上游沟岸滑坡产生的松散物共同组成2018年7月11日泥石流的启动物源, 灾前连续两天降水使得物源含水量达到饱和, 土体抗剪强度降低, 灾害当天持续小雨诱发高位物源启动, 形成泥石流灾害.天摩沟冰川对泥石流发育的作用在于贡献了部分物源和水源.其流速明显高于周边冰川, 主干峰值流速可达0.80±0.02 m·d^-1.冰川高速流动使得高位冰碛物堆积速度快, 而冰川融水使得泥石流降雨启动阈值更低.天摩沟在2018年7月之后没有再发生大规模泥石流, 但是主沟中上游及中游两侧坡体陡峭且岩性松散, 在雨水和冰雪融水作用下极易垮塌.无人机像片显示目前主沟中游沟底已经累积一定量的松散物.同时天摩沟冰川的流动会持续增加高位冰碛物体积.如果沟内物源累积到一定程度, 强降雨仍会诱发泥石流.

     

Method to improve the mitigative effectiveness of a series of check dams against debris flows

The advance of technology has led to more competent countermeasures, but lives and properties still continue to suffer from water‐induced disasters, such as floods, landslides, and debris flows. To increase the effectiveness of counter systems, improved methods of planning and designing such systems are prerequisite. This paper describes briefly a methodological approach for predicting debris flow characteristics, and proposes techniques for evaluating and improving the mitigative effectiveness of check dams against debris flows in steep mountain torrents. Additionally, a non‐dimensional parameter, namely potential storage volume, is introduced to generalize the evaluation processes. As an example, the 1999 debris‐flow event in the San Julian River, Venezuela, is chosen for discussion. The paper also proposes a method of evaluating the control function of a series of check dams as well as the criteria for the selection of their sizes, numbers and locations. It is hoped that this work will help to determine which combinations of check dams will fit best together for the optimal control of debris flows and available resources in any river basin. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of forest harvesting on the occurrence of landslides and debris flows in steep terrain of central Japan

Landslides and debris flows associated with forest harvesting can cause much destruction and the influence of the timing of harvesting on these mass wasting processes therefore needs to be assessed in order to protect aquatic ecosystems and develop improved strategies for disaster prevention. We examined the effects of forest harvesting on the frequency of landslides and debris flows in the Sanko catchment (central Japan) using nine aerial photo periods covering 1964 to 2003. These photographs showed a mosaic of different forest ages attributable to the rotational management in this area since 1912. Geology and slope gradient are rather uniformly distributed in the Sanko catchment, facilitating assessment of forest harvesting effects on mass wasting without complication of other factors. Trends of new landslides and debris flows correspond to changes in slope stability explained by root strength decay and recovery; the direct impact of clearcutting on landslide occurrence was greatest in forest stands that were clearcut 1 to 10 yr earlier with progressively lesser impacts continuing up to 25 yr after harvesting. Sediment supply rate from landslides in forests clearcut 1 to 10 yr earlier was about 10‐fold higher than in control sites. Total landslide volume in forest stands clearcut 0 to 25 yr earlier was 5·8 × 10³ m³ km^?2 compared with 1·3 × 10³ m³ km^?2 in clearcuts >25 yr, indicating a fourfold increase compared with control sites during the period when harvesting affected slope stability. Because landslide scars continue to produce sediment after initial failure, sediment supply from landslides continues for 45 yr in the Sanko catchment. To estimate the effect of forest harvesting and subsequent regeneration on the occurrence of mass wasting in other regions, changes in root strength caused by decay and recovery of roots should be investigated for various species and environmental conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

A 2D finite volume model for bebris flow and its application to events occurred in the Eastern Pyrenees

FLATModel is a 2D finite volume code that contains several original approaches to improve debris-flow simulation. Firstly, FLATModel incorporates a ＂stop-and-go＂ technique in each cell to allow continuous collapses and remobilizations of the debris-flow mass. Secondly, flow velocity and consequently yield stress is directly associated with the type of rheology to improve boundary accuracy. Thirdly, a simple approach for entrainment is also included in the model to analyse the effect of basal erosion of debris flows. FLATMODEL was tested at several events that occurred in the Eastern Pyrenees and simulation results indicated that the model can represent rather well the different characteristics observed in the field.     

Age of the oldest hominin settlements in Spain: Contribution of the combined U-series/ESR dating method applied to fossil teeth

This paper presents a synthesis of the combined Uranium-Series/ESR age results obtained on fossil teeth from several Early Pleistocene archaeological and/or palaeontological Spanish localities: Atapuerca Gran Dolina TD-6, Fuente Nueva-3, Barranco León, Venta Micena and Vallparadís. While the age results show some scattering, they are nevertheless encouraging and provide a significant contribution to the understanding of the first hominin settlements in Western Europe.These “old” samples are mainly characterised by high ²³⁰Th/²³⁴U activity ratios that may sometimes exceed secular equilibrium, and by high Uranium concentrations (several tens of ppm or more). The modelling of U-uptake is therefore really crucial for the age calculation process. In the case of the combined US–ESR approach, this uptake is derived from the U-series data measured in dental tissues, which seem to be strongly dependant on the hydro-geological context. Consequently, when dating “old” samples, a special attention has to be paid to the accuracy and the meaning of the U-series data collected from the dental tissues, which may be influenced by several factors such as spatial heterogeneity and recent U-uptake overprint. Some rapid scanning procedures should be developed in order to pre-identify the samples that are the most suitable for ESR dating.     

Surface exposure dating of Holocene basalt flows and cinder cones in the Kula volcanic field (Western Turkey) using cosmogenic 3He and 10Be

The Kula volcanic field in Western Turkey comprises about 80 cinder cones and associated basaltic lava flows of Quaternary age. Based on geomorphological criteria and K-Ar dating, three eruption phases, β2–β4, were distinguished in previous studies. Human footprints in ash deposits document that the early inhabitants of Anatolia were affected by the volcanic eruptions, but the age of the footprints has been poorly constrained. Here we use ³He and ¹⁰Be exposure dating of olivine phenocrysts and quartz-bearing xenoliths to determine the age of the youngest lava flows and cinder cones. In the western part of the volcanic field, two basalt samples from a 15-km-long block lava flow yielded ³He ages of 1.5 ± 0.3 ka and 2.5 ± 0.4 ka, respectively, with the latter being in good agreement with a ¹⁰Be age of 2.4 ± 0.3 ka for an augen gneiss xenolith from the same flow. A few kilometers farther north, a metasedimentary xenolith from the top of the cinder cone Çakallar Tepe gave a ¹⁰Be age of 11.2 ± 1.1 ka, which dates the last eruption of this cone and also the human footprints in the related ash deposits. In the center of the volcanic field, a basalt sample and a metasedimentary xenolith from another cinder cone gave consistent ³He and ¹⁰Be ages of 2.6 ± 0.4 ka and 2.6 ± 0.3 ka, respectively. Two β4 lava flows in the central and eastern part of the volcanic province yielded ³He ages of 3.3 ± 0.4 ka and 0.9 ± 0.2 ka, respectively. Finally, a relatively well-preserved β3 flow gave a ³He age of ∼13 ka. Taken together, our results demonstrate that the penultimate eruption phase β3 in the Kula volcanic field continued until ∼11 ka, whereas the youngest phase β4 started less than four thousand years ago and may continue in the future.     

Earthen barriers to control lava flows in the 2001 eruption of Mt. Etna

Preceded by four days of intense seismicity and marked ground deformation, a new eruption of Mt. Etna started on 17 July and lasted until 9 August 2001. It produced lava emission and strombolian and phreatomagmatic activity from four different main vents located on a complex fracture system extending from the southeast summit cone for about 4.5 km southwards, from 3000 to 2100 m elevation (a.s.l.). The lava emitted from the lowest vent cut up an important road on the volcano and destroyed other rural roads and a few isolated country houses. Its front descended southwards to about 4 km distance from the villages of Nicolosi and Belpasso. A plan of intervention, including diversion and retaining barriers and possibly lava flow interruption, was prepared but not activated because the flow front stopped as a consequence of a decrease in the effusion rate. Extensive interventions were carried out in order to protect some important tourist facilities of the Sapienza and Mts. Silvestri zones (1900 m elevation) from being destroyed by the lava emitted from vents located at 2700 m and 2550 m elevation. Thirteen earthen barriers (with a maximum length of 370 m, height of 10–12 m, base width of 15 m and volume of 25 000 m³) were built to divert the lava flow away from the facilities towards a path implying considerably less damage. Most of the barriers were oriented diagonally (110–135°) to the direction of the flow. They were made of loose material excavated nearby and worked very nicely, resisting the thrust of the lava without any difficulty. After the interventions carried out on Mt. Etna in 1983 and in 1991–1992, those of 2001 confirm that earthen barriers can be very effective in controlling lava flows.     

A water balance study of the upper White Nile basin flows in the late nineteenth century

Abstract

A water balance model of the Nile is described, working in terms of dry season flows. The main use of the modelling studies was to extend flows back to the start of observations at Aswan in 1869, and hence to estimate the levels of Lake Victoria during the high flow event of the 1870s. New estimates of Lake Victoria levels and outflows for the period 1870–1895 are deduced, extending the length of the observed data for Lake Victoria by some 25%. Crucially, the analysis includes the major flood event of 1878, which historical evidence suggests was the highest since 1860 or earlier. The modelling results are compared with previous estimates and a detailed examination of historical evidence. Some prospects for future levels are considered, taking into account the reconstructed levels of the late nineteenth century.     

A comparison of the reflectivity method and full wave theory as applied to SH diffraction around the core

Summary To derive the structure of the Lower Mantle, observations of P and S waves at epicentral distances beyond 90 degrees have been used. The arrival times and amplitude decay with distance proved to be a source of information to derive the structure near the core-mantle interface. These observations were compared with results of theoretical calculations based on full wave theory [1, 2, 5, 6]. Another important theoretical method is the reflectivity method [4]. Differences between the two methods have a direct bearing on the interpretation of the observations and therefore need to be investigated.In the two methods the wave propagation involved in diffraction is simulated in different ways. In this paper the importance of approximations involved in each of the methods will be discussed. For this purpose the calculation of the frequency-dependent decay with distance of diffracted SH waves has been chosen. The approximations are considered to be important both in P and SH diffraction. The advantage of studying SH waves is the simpler and more straightforward formulation.