scholarly journals Genesis and provenance of a new Middle Pleistocene diamicton unit at Happisburgh, NE Norfolk, UK

2016 ◽  
Vol 61 (1) ◽  
pp. 25-35 ◽  
Author(s):  
Richard G. Hodkin ◽  
Jonathan R. Lee ◽  
James B. Riding ◽  
Jenni A. Turner
Keyword(s):  
Debris Flows ◽  
Mass Movement ◽  
Dam Failure ◽  
Middle Pleistocene ◽  
Intense Rainfall ◽  
Outburst Flood ◽  
Trigger Mechanism ◽  
Water Saturated ◽  
Seasonal Melting ◽  
Moraine Dam Failure

Glacigenic deposits at Happisburgh, NE Norfolk, record the earliest known expansion of glaciers into lowland eastern England during the Quaternary. The sequence comprises two regionally extensive till units, the Happisburgh Till and Corton Diamicton members of the Happisburgh Glacigenic Formation, deposited during separate ice advances, and intervening glacilacustrine and outwash deposits laid down during ice-marginal retreat. During 2012, a new diamicton unit was discovered within the intervening sorted sediments and its significance is outlined here. Sedimentological and structural evidence suggests, tentatively, that the diamicton forms a small debris fan generated subaerially by a series of water-saturated hyperconcentrated or debris flows. The precise trigger mechanism for these flow deposits remains unclear, but may relate to seasonal melting of surface or buried ice followed by mass-movement, or to more abrupt geological events including periods of intense rainfall, moraine dam failure or a glacier outburst flood.

scholarly journals An approach for estimating the breach probabilities of moraine-dammed lakes in the Chinese Himalayas using remote-sensing data

2012 ◽  
Vol 12 (10) ◽  
pp. 3109-3122 ◽  
Author(s):  
X. Wang ◽  
S. Liu ◽  
Y. Ding ◽  
W. Guo ◽  
Z. Jiang ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Decision Making ◽  
Expert Knowledge ◽  
Remote Sensing Data ◽  
Dam Failure ◽  
Outburst Flood ◽  
First Order ◽  
Trigger Mechanisms ◽  
Very High ◽  
Moraine Dam Failure

Abstract. To make first-order estimates of the probability of moraine-dammed lake outburst flood (MDLOF) and prioritize the probabilities of breaching posed by potentially dangerous moraine-dammed lakes (PDMDLs) in the Chinese Himalayas, an objective approach is presented. We first select five indicators to identify PDMDLs according to four predesigned criteria. The climatic background was regarded as the climatic precondition of the moraine-dam failure, and under different climatic preconditions, we distinguish the trigger mechanisms of MDLOFs and subdivide them into 17 possible breach modes, with each mode having three or four components; we combined the precondition, modes and components to construct a decision-making tree of moraine-dam failure. Conversion guidelines were established so as to quantify the probabilities of components of a breach mode employing the historic performance method combined with expert knowledge and experience. The region of the Chinese Himalayas was chosen as a study area where there have been frequent MDLOFs in recent decades. The results show that the breaching probabilities (P) of 142 PDMDLs range from 0.037 to 0.345, and they can be further categorized as 43 lakes with very high breach probabilities (P ≥ 0.24), 47 lakes with high breach probabilities (0.18 ≤ P < 0.24), 24 lakes with mid-level breach probabilities (0.12 ≤ P < 0.18), 24 lakes with low breach probabilities (0.06 ≤ P < 0.12), and four lakes with very low breach probabilities (p < 0.06).

scholarly journals Influence of biopolymers on the rheological properties of seafloor sediments and the runout behavior of submarine debris flows

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jun Kameda ◽  
Hamada Yohei
Keyword(s):  
Rheological Properties ◽  
Debris Flows ◽  
Extracellular Polymeric Substances ◽  
Flow Behavior ◽  
Mass Movement ◽  
Rheological Parameters ◽  
Natural Environments ◽  
Natural Systems ◽  
Chemical Conditions ◽  
Seafloor Sediments

AbstractSubmarine debris flows are mass movement processes on the seafloor, and are geohazards for seafloor infrastructure such as pipelines, communication cables, and submarine structures. Understanding the generation and run-out behavior of submarine debris flows is thus critical for assessing the risk of such geohazards. The rheological properties of seafloor sediments are governed by factors including sediment composition, grain size, water content, and physico-chemical conditions. In addition, extracellular polymeric substances (EPS) generated by microorganisms can affect rheological properties in natural systems. Here we show that a small quantity of EPS (~ 0.1 wt%) can potentially increase slope stability and decrease the mobility of submarine debris flows by increasing the internal cohesion of seafloor sediment. Our experiments demonstrated that the flow behavior of sediment suspensions mixed with an analogue material of EPS (xanthan gum) can be described by a Herschel–Bulkley model, with the rheological parameters being modified progressively, but not monotonously, with increasing EPS content. Numerical modeling of debris flows demonstrated that the run-out distance markedly decreases if even 0.1 wt% of EPS is added. The addition of EPS can also enhance the resistivity of sediment to fluidization triggered by cyclic loading, by means of formation of an EPS network that binds sediment particles. These findings suggest that the presence of EPS in natural environments reduces the likelihood of submarine geohazards.

scholarly journals How nutrient rich are decaying cocoa pod husks? The kinetics of nutrient leaching

2021 ◽  
Author(s):  
D.-G. J. M. Hougni ◽  
A. G. T. Schut ◽  
L. S. Woittiez ◽  
B. Vanlauwe ◽  
K. E. Giller
Keyword(s):  
Nutrient Release ◽  
Nutrient Content ◽  
Nutrient Leaching ◽  
Intense Rainfall ◽  
Decomposition Rates ◽  
Rainfall Events ◽  
Rainfall Frequency ◽  
Water Saturated ◽  
Kinetics Of ◽  
Cocoa Pod Husks

Abstract Aim Recycling of cocoa pod husks has potential to contribute to mineral nutrition of cocoa. Yet little is known of the nutrient content and nutrient release patterns from the husks. The potassium (K) rich husks are usually left in heaps in cocoa plantations in Africa. We aimed to understand and quantify release patterns of K and other nutrients from husks under varying rainfall regimes and assessed the effects of partial decomposition and inundation on nutrient leaching rates. Methods We incubated chunks of cocoa pod husks to assess decomposition rates and we measured nutrient leaching rates from two sets of husk chunks: one set was placed in tubes that were submitted to simulated scheduled rainfall events while the second set was continuously inundated in beakers. Results Decomposition of husks followed a second-order exponential curve (k: 0.09 day−1; ageing constant: 0.43). Nutrient losses recorded within 25 days were larger and more variable for K (33%) than for other macronutrients released in this order: Mg > Ca ≈ P > N (less than 15%). Potassium leaching was mainly driven by rainfall frequency (P < 0.05) and reinforced by intense rainfall, especially at lower frequency. Under water-saturated conditions, 11% of K was leached out within 48 h from fresh husks compared with 92% from partially decayed husks. Conclusion Some initial decomposition of cocoa pod husks is required to expose K to intense leaching. As decomposition progresses, abundant K losses are to be expected under frequent and/or intense rainfall events.

scholarly journals 2D Runout Modelling of Hillslope Debris Flows, Based on Well-Documented Events in Switzerland

Geosciences ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 70 ◽  
Author(s):  
Florian Zimmermann ◽  
Brian W. McArdell ◽  
Christian Rickli ◽  
Christian Scheidl
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Mass Movement ◽  
Clay Content ◽  
Systematic Evaluation ◽  
Mountain Areas ◽  
Flow Processes ◽  
Friction Parameters ◽  
Cohesive Interaction ◽  
Hillslope Debris Flow

In mountain areas, mass movements, such as hillslope debris flows, pose a serious threat to people and infrastructure, although size and runout distances are often smaller than those of debris avalanches or in-channel-based processes like debris floods or debris flows. Hillslope debris-flow events can be regarded as a unique process that generally can be observed at steep slopes. The delimitation of endangered areas and the implementation of protective measures are therefore an important instrument within the framework of a risk analysis, especially in the densely populated area of the alpine region. Here, two-dimensional runout prediction methods are helpful tools in estimating possible travel lengths and affected areas. However, not many studies focus on 2D runout estimations specifically for hillslope debris-flow processes. Based on data from 19 well-documented hillslope debris-flow events in Switzerland, we performed a systematic evaluation of runout simulations conducted with the software Rapid Mass Movement Simulation: Debris Flow (RAMMS DF)—a program originally developed for runout estimation of debris flows and snow avalanches. RAMMS offers the possibility to use a conventional Voellmy-type shear stress approach to describe the flow resistance as well as to consider cohesive interaction as it occurs in the core of dense flows with low shear rates, like we also expect for hillslope debris-flow processes. The results of our study show a correlation between the back-calculated dry Coulomb friction parameters and the percentage of clay content of the mobilised soils. Considering cohesive interaction, the performance of all simulations was improved in terms of reducing the overestimation of the observed deposition areas. However, the results also indicate that the parameter which accounts for cohesive interaction can neither be related to soil physical properties nor to different saturation conditions.

scholarly journals Analysis of River Blocking Induced by a Debris Flow

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Lijuan Wang ◽  
Ming Chang ◽  
Xiangyang Dou ◽  
Guochao Ma ◽  
Chenyuan Yang
Keyword(s):  
Debris Flow ◽  
Return Period ◽  
Debris Flows ◽  
Small Volume ◽  
Disaster Prevention ◽  
Intense Rainfall ◽  
Residential Areas ◽  
The Wenchuan Earthquake ◽  
Movement Characteristics ◽  
Blocking Event

Both the Wenchuan earthquake on May 12, 2008, and the Lushan earthquake on April 12, 2013, produced many coseismic landslides along the Nanya River in Shimian City. Subsequent debris flows that initiated from these landslides and are triggered by intense rainfall become the secondary hazard in the years after the earthquake; in particular, some debris flows led to a serious river blocking event. For example, the Guangyuanbao debris flow which occurred on July 04, 2013, partly blocked the Nanya River, presenting a major threat to the national highway and residential areas. To analyze the pattern of landslide damming, we analyzed numerical simulations of the movement characteristics of the Guangyuanbao debris flow using rainfall intensities with varying recurrence periods of 5, 20, and 50 years. The accuracy of the spreading of the numerical simulation is about 90%. The simulation indicated a small volume of sediment entering the river for a rainfall under 5-year return period. A debris flow induced by rainfall under 20-year return period partly blocked the river, while rainfall under 50-year return period has potential to block the river completely. This proposed analysis of river blocking induced by a debris flow could be used for disaster prevention in earthquake-stricken area.

Swelling clayey soils promote slope instability in the Muhunguzi watershed, western Burundi

2020 ◽  
Author(s):  
Bruno Delvaux ◽  
Clairia Kankurize ◽  
Gervais Rufyikiri
Keyword(s):  
Clay Minerals ◽  
Clay Fraction ◽  
Slope Instability ◽  
Atterberg Limits ◽  
Intense Rainfall ◽  
Angle Of Friction ◽  
Red Soils ◽  
Soil Cohesion ◽  
Internal Angle ◽  
Water Saturated

&lt;p&gt;In Burundi, landslides are frequent on the western slope of the Congo-Nile ridge. Unfortunately, they are poorly studied and understood despite their deadly consequences. Previous reports have suggested that slope steepness, lithology and clay soils expose this slope to landslides, while heavy and intense rainfall is a trigger. However, the role of soil in the vulnerability of this specific slope to landslides is unknown. Here we investigate on soil characteristics involved in land sliding in this area.&lt;/p&gt;&lt;p&gt;We selected and sampled black and red soils in two Muhunguzi landslides. We determined the soil plasticity from Atterberg limits as well as the particle size distribution. In addition, we measured the soil weathering stage, and further identified the clay minerals from measuring the cation exchange capacity of the clay fraction and analyzing clay samples with X-ray diffraction (XRD).&lt;/p&gt;&lt;p&gt;Both the black and red soils are moderately weathered since TRB values in the B horizons range between 330 and 425 cmol(+) kg&lt;sup&gt;-1&lt;/sup&gt;. The soils are loamy clayey to clayey (% clay: 33-55%), and contain high charge clay minerals. They do not differ in their Atterberg limits, which classify the soils as medium plasticity soils in the Casagrande plasticity diagram. Our data further show that both soils have a medium swelling potential. XRD show that the clay fraction consists of kaolinite and smectite and/or vermiculite. The latter 2:1 clay minerals are expandable and swelling clays, respectively. They give these two soils their plasticity and swelling properties. These two properties play an important role in the mechanical behavior of water-saturated soils. Indeed, swelling reduces soil cohesion while the plasticity index and the liquidity limit vary inversely with the internal angle of friction of the soil; cohesion and internal angle of friction being the fundamental parameters of the soil shear resistance. In addition, the soil mantle covers a hard schistose rock whose declivity is parallel to the soil surface slope. Thus, after intense rainfall during the wet season, the water-saturated soil reaches a level of liquidity sufficient to favor a landslide, all the more easily if the slope of the hard rock is inclined in the direction of the gravity flow.gru&lt;/p&gt;

Hazards on Dujiangyan-Wenchuan Highways Induced by Catastrophic Debris Flows on July 10 2013 and Prevention

2014 ◽  
Vol 501-504 ◽  
pp. 2463-2472 ◽  
Author(s):  
Yong Gang Ge ◽  
Qiang Zou ◽  
Jian Qiang Zhang ◽  
Xiao Jun Guo
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Large Scale ◽  
Integrated Management ◽  
Gansu Province ◽  
Chain Process ◽  
Outburst Flood ◽  
Protection Measures ◽  
Traffic Security ◽  
Dangerous Section

After the Wenchuan Earthquake on May 12 2008, the highways from Dujiangyan to Wenchuan, a crucial passage from Chengdu to Sichuan Western Plateau and Gansu province, are always seriously endangered by landslides, debris flows and their following hazards. Hundreds of debris flows from watersheds, gullies and slopes on July 10 2013 produced fatal hazards and destruction on the Highway G213 and the Express Highway from Yingxiu to Wenchuan. The debris flows are characterized by numerous-occurrence, large flux (645~2238m3/s) and large magnitude (5~126×104m3) as well as the hazard chain process which is composed of debris flow, dammed lake and outburst flood. The highways were seriously destructed and blocked in 16 sites, which were induced by 6 collapsed bridges, 3 submerged bridges, 3 buried tunnel entrances, 1 site collapsed highway base and 7 sites buried highway base or bridges, and the traffic was completely interrupted. Based on analyzing the destruction modes of highways, it was found that the large-scale and potential debris flows and the irrational location of some sections, vulnerable protection measures and low resistant capability of highways against debris flows were responsible for huge highway destructions. Considering the active debris flows in the future at least 5~10 years, it was strongly suggested that potential debris flow identification, integrated management of disastrous watershed, dangerous road line altering, increasing and strengthening protection constructions at dangerous section and improving highway reconstruction standard should be carried out for highway protection and traffic security.

scholarly journals Intense rainfall and debris flows in the Lomond Hills, Fife, 11–12 August 2020

2021 ◽  
pp. 1-18
Author(s):  
M. P. Kirkbride ◽  
A. R. Black ◽  
V. Brazier ◽  
B. S. Pickering
Keyword(s):  
Debris Flows ◽  
Intense Rainfall

scholarly journals Climate change and the global pattern of moraine-dammed glacial lake outburst floods

2017 ◽  
Author(s):  
Stephan Harrison ◽  
Jeffrey S. Kargel ◽  
Christian Huggel ◽  
John Reynolds ◽  
Dan H. Shugar ◽  
...  
Keyword(s):  
Climate Change ◽  
Ice Age ◽  
Dam Failure ◽  
Glacial Lake ◽  
Glacier Recession ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods ◽  
Lake Formation ◽  
Recent Climate ◽  
Moraine Dam Failure

Abstract. Despite recent research identifying a clear anthropogenic impact on glacier recession, the effect of recent climate change on glacier-related hazards is at present unclear. Here we present the first global spatio-temporal assessment of glacial lake outburst floods (GLOFs) focusing explicitly on lake drainage following moraine dam failure. These floods occur as mountain glaciers recede and downwaste and many have an enormous impact on downstream communities and infrastructure. Our assessment of GLOFs associated with the collapse of moraine-dammed lakes provides insights into the historical trends of GLOFs and their distributions under current and future global climate change. We observe a clear global increase in GLOF frequency and their regularity around 1930, which likely represents a lagged response to post-Little Ice Age warming. Notably, we also show that GLOF frequency and their regularity – rather unexpectedly – has declined in recent decades even during a time of rapid glacier recession. Although previous studies have suggested that GLOFs will increase in response to climate warming and glacier recession, our global results demonstrate that this has not yet clearly happened. From assessment of the timing of climate forcing, lag times in glacier recession, lake formation and moraine dam failure, we predict increased GLOF frequencies during the next decades and into the 22nd century.

scholarly journals Scenarios calculations of outburst flood and debris flows

2021 ◽  
Vol 834 (1) ◽  
pp. 012009
Author(s):  
VA Kurovskaia ◽  
SS Chernomorets ◽  
TA Vinogradova ◽  
IN Krylenko ◽  
AG Ghulomaidarov ◽  
...  
Keyword(s):  
Debris Flows ◽  
Outburst Flood
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