scholarly journals Temporal Relationship of Increased Palaeodischarges and Late Glacial Deglaciation Phases on the Catchment of River Maros/Mureş, Central Europe

2021 ◽  
Vol 14 (3-4) ◽  
pp. 39-46
Author(s):  
Tamás Bartyik ◽  
György Sipos ◽  
Dávid Filyó ◽  
Tímea Kiss ◽  
Petru Urdea ◽  
...  
Keyword(s):  
Late Glacial ◽  
Alluvial Fan ◽  
Activity Period ◽  
Sediment Delivery ◽  
High Discharge ◽  
Bankfull Discharge ◽  
Temporal Relationships ◽  
Glacial Runoff ◽  
Relationship Of ◽  
Increasing Precipitation

Abstract River Maros/Mureş has one of the largest alluvial fans in the Carpathian Basin. On the surface of the fan several very wide, braided channels can be identified, resembling increased discharges during the Late Glacial. In our study we investigated the activity period of the largest channel of them, formed under a bankfull discharge three times higher than present day values. Previous investigations dated the formation of the palaeochannel to the very end of the Pleistocene by dating a point bar series upstream of the selected site. Our aim was to obtain further data on the activity period of the channel and to investigate temporal relationships between maximum palaeodischarges, deglaciation phases on the upland catchment and climatic amelioration during the Late Pleistocene. The age of sediment samples was determined by optically stimulated luminescence (OSL). The investigation of the luminescence properties of the quartz extracts also enabled the assessment of sediment delivery dynamics in comparison to other palaeochannels on the alluvial fan. OSL age results suggest that the activity of the channel is roughly coincident with, but slightly older than the previously determined ages, meaning that the main channel forming period started at 13.50±0.94 ka and must have ended by 8.64±0.82 ka. This period cannot directly be related to the major phases of glacier retreat on the upland catchments, and in terms of other high discharge channels only the activity of one overlaps with a major deglaciation phase at ~17-18 ka. Based on these, high palaeodischarges can be rather related to increased Late Glacial runoff, resulted by increasing precipitation and scarce vegetation cover on the catchment. Meanwhile, the quartz luminescence sensitivity of the investigated channel refers to fast sediment delivery from upland subcatchments. Therefore, the retreat of glaciers could affect alluvial processes on the lowland by increasing sediment availability, which contributed to the development of large braided palaeochannels.

Late Glacial, Early Holocene and Late Holocene life at the interface of a distinct landscape — relationship of humans and environments in the Sub-Carpathian region (N Hungary)

2012 ◽  
Vol 4 (4) ◽  
Author(s):  
Gábor Bácsmegi ◽  
Pál Sümegi ◽  
Tünde Törőcsik
Keyword(s):  
Water Level ◽  
Late Holocene ◽  
Late Glacial ◽  
Climatic Effects ◽  
Natural Landscape ◽  
Carpathian Region ◽  
Modern Age ◽  
Reed Bed ◽  
Relationship Of ◽  
Historical Methods

AbstractRelationships between the communities and environment surrounding these communities can be disclosed by the application of different archeological, geological and environmental historical methods. This includes the deployment of numerous tools in scientific investigation including the application of chronological, sedimentological, geochemical and paleoecological analytical methods on sequences accumulated in historical catchment basins of peat-bog. The Nádas-tó at Nagybárkány is a small peatbog in the northern part of Hungary, on the Sub-Carpathian region. The formation of the lake can be traced back to the Late Glacial period. The sediments deposited in the lakebed provide a record of climatic and hydrologic changes. A higher water level could be demonstrated from the Late Glacial to the Mid-Holocene, when the reed-beds covered a small area only. This was followed by a hiatus spanning ca. 4400 years, caused by the deepening and cleaning of the lakebed during the Late Iron / Imperial Age, between 2100 - 1900 cal BP years. After this change the water level decreased and the water quality was more eutrophic. A reed-bed evolved around the lake. Paludification started with a bulrush floating mat phase at the close of the Middle Age, ca. 1500 cal AD years. The endowments and settlement pattern persisted from the Neolithic onwards until the terminal Modern Age, when measures aimed to ordain the area substantially altered the natural landscape. Although some anthropogenic disturbances can be reconstructed in the development of the peatland, some climatic effects and authogenic processes might be separated by paleoecological analyses.

scholarly journals Seedability of Winter Orographic Clouds

1986 ◽  
Vol 43 ◽  
pp. 127-138 ◽  
Author(s):  
Geoffrey E. Hill
Keyword(s):  
Wind Speed ◽  
Liquid Water ◽  
Supercooled Liquid ◽  
Direct Measurements ◽  
Orographic Clouds ◽  
The Subject ◽  
Relationship Of ◽  
Increasing Precipitation ◽  
Cloud Top Temperature ◽  
Limiting Value

Abstract This article is a review of work on the subject of seedability of winter orographic clouds for increasing precipitation. Various aspects of seedability are examined in the review, including definitions, distribution of supercooled liquid water, related meteorological factors, relationship of supercooled liquid water to storm stage, factors governing seedability, and the use of seeding criteria. Of particular interest is the conclusion that seedability is greatest when supercooled liquid water concentrations are large and at the same time precipitation rates are small. Such a combination of conditions is favored if the cloud-top temperature is warmer than a limiting value and as the cross-barrier wind speed at mountaintop levels increases. It is also suggested that cloud seeding is best initiated in accordance with direct measurements of supercooled liquid water, precipitation, and cross-barrier wind speed. However, in forecasting these conditions or in continuation of seeding previously initiated, the cloud-top temperature and cross-barrier wind speed are the most useful quantities.

Paleoearthquakes on the Húsavík-Flatey Fault in northern Iceland: Where are the large earthquakes?

2021 ◽  
Author(s):  
Remi Matrau ◽  
Yann Klinger ◽  
Jonathan Harrington ◽  
Ulas Avsar ◽  
Esther R. Gudmundsdottir ◽  
...  
Keyword(s):  
Slip Rate ◽  
Late Glacial ◽  
Fault Scarp ◽  
Alluvial Fan ◽  
Tectonic Deformation ◽  
Birch Wood ◽  
Alluvial Deposits ◽  
Slip Rates ◽  
Tephra Layers ◽  
Large Earthquakes

<p>Paleoseismology is key to study earthquake recurrence and fault slip rates during the Late Pleistocene-Holocene. The Húsavík-Flatey Fault (HFF) in northern Iceland is a 100 km-long right-lateral transform fault connecting the onshore Northern Volcanic Zone to the offshore Kolbeinsey Ridge and accommodating, together with the Grímsey Oblique Rift (GOR), ~18 mm/yr of relative motion between the Eurasian and North American plates. Significant earthquakes occurred on the HFF in 1755, 1838 and 1872 with estimated magnitudes of 6.5-7. However, historical information on past earthquakes prior to 1755 is very limited in both timing and size.</p><p>We excavated five trenches in a small basin (Vestari Krubbsskál) located 5.5 km southeast of the town of Húsavík and at 300 m.a.s.l. and one trench in an alluvial fan (Traðargerði) located 0.5 km north of Húsavík and at 50 m.a.s.l. In a cold and wet environment, such as in coastal parts of Iceland, one has to take into account periglacial processes affecting the topsoil to discriminate tectonic from non-tectonic deformation. We used tephra layers in the Vestari Krubbsskál and Traðargerði trenches as well as birch wood samples in Traðargerði to constrain the timing of past earthquakes. Tephra layers Hekla-3 (2971 BP) and Hekla-4 (4331±20 BP) are visible in the top half of all the trenches. In addition, a few younger tephra layers are visible in the top part of the trenches. In Traðargerði several dark layers rich in organic matter are found, including birch wood-rich layers from the Earlier Birch Period (9000-7000 BP) and the Later Birch Period (5000-2500 BP). In Vestari Krubbsskál the lower halves of the trenches display mostly lacustrine deposits whereas in Traðargerði the lower half of the trench shows alluvial deposits overlaying coarser deposits (gravels/pebbles) most likely of late-glacial or early post-glacial origins. In addition, early Holocene tephra layers are observed in some of the trenches at both sites and may correspond to Askja-S (10800 BP), Saksunarvatn (10300 BP) and Vedde (12100 BP). These observations provide good age constraints and suggest that both the Vestari Krubbsskál and Traðargerði trenches cover the entire Holocene.</p><p>Trenches at both sites show significant normal deformation in addition to strike-slip, well correlated with their larger scale topographies (pull-apart basin in Vestari Krubbsskál and 45 m-high fault scarp in Traðargerði). We mapped layers, cracks and faults on all trench walls to build a catalogue of Holocene earthquakes. We identified events based on the upward terminations of the cracks and retrodeformation. Our results yield fewer major earthquakes than expected, suggesting that large earthquakes (around magnitude 7) are probably rare and the more typical HFF earthquakes of magnitude 6-6.5 likely produce limited topsoil deformation.[yk1]  Our interpretation also suggests that the Holocene slip rate [yk2] for the fault section we are studying may be slower than the estimated geodetic slip rate (6 to 9 mm/yr)[yk3]  for the entire onshore HFF, although secondary onshore sub-parallel fault strands could accommodate part of the deformation.</p>

Influence of Wildfire on Earth Surface Processes and Geomorphology

2021 ◽  
Author(s):  
Paul Santi ◽  
Francis Rengers
Keyword(s):  
Debris Flows ◽  
Management Practices ◽  
Mass Movement ◽  
Soil Formation ◽  
Alluvial Fan ◽  
Water Repellent ◽  
Alluvial Fans ◽  
Stream Channels ◽  
Sediment Delivery ◽  
Recurrence Intervals

<p>Wildfire is a global phenomenon that is expected to increase in extent and severity due to shifting land management practices and climate change. It removes vegetation, deposits ash, influences water-repellent soil formation, and physically weathers rock. These changes typically lead to increased erosion through sheetwash, rilling, rock spalling, and dry ravel, as well as increased mass movement in the form of floods, debris flows, rockfall, and landslides. Post-wildfire changes in these processes bring about landform changes as hillslopes are lowered and stream channels aggrade or incise at increased rates. Research has documented increases in erosion after wildfire ranging from 2-1000 times the pre-fire rates. Post-wildfire landscape lowering by erosion has been measured in the western U.S. at magnitudes of 2 mm per year, with sediment delivery at the mouths of canyons increased in the range of 160-1000% during the post-wildfire window of disturbance. Furthermore, post-wildfire sediment transport enhances the development of alluvial fans, debris fans, and talus cones. Debris-flow likelihood is increased following wildfire, such that modest rainstorms with <2 year recurrence intervals are typically sufficient to trigger debris flows with volumes much larger (270-540%) than at unburned sites. In the western U.S., as much as 25-50% of alluvial fan accumulation can be attributed to post-wildfire debris flows and other post-wildfire fluvial transport. The window of disturbance to the landscape caused by wildfire is typically on the order of three to four years, with some effects persisting up to 30 years.  Consequently, wildfire is an important agent of geomorphic change.</p>

scholarly journals The 9 September 2010 torrential rain and flash flood in the Dragone catchment, Atrani, Amalfi Coast (southern Italy)

2016 ◽  
Vol 16 (2) ◽  
pp. 333-348 ◽  
Author(s):  
C. Violante ◽  
G. Braca ◽  
E. Esposito ◽  
G. Tranfaglia
Keyword(s):  
Southern Italy ◽  
Flash Flood ◽  
Alluvial Fan ◽  
Convective System ◽  
Sediment Delivery ◽  
Geologic Hazard ◽  
Field Evidence ◽  
Load Transport ◽  
Bed Load Transport ◽  
Coastal Range

Abstract. In this paper we use a multi-hazard approach to analyse the 9 September 2010 flash flood in the Dragone basin, a 9 km2 catchment located along the Amalfi rocky coastal range, southern Italy. In this area, alluvial fan flooding has been the most frequent and destructive geologic hazard since Roman times. Sudden torrents of water (flash floods) are caused by high-intensity and very localized cloudbursts of short duration, inducing slope erosion and sediment delivery from slope to stream. The elevated bed load transport produces fast-moving hyperconcentrated flows with significant catastrophic implications for communities living at the stream mouth. The 9 September 2010 rainstorm event lasted 1 h with an intensity rainfall peak of nearly 120 mm h−1. High topographic relief of the Amalfi coastal range and positive anomalies of the coastal waters conditioned the character of the convective system. Based on geological data and post-event field evidence and surveys, as well as homemade videos and eyewitness accounts, it is reported that the flash flood mobilized some 25 000 m3 of materials with a total (water and sediment) peak flow of 80 m3 s−1. The estimated peak discharge of only clear water was about 65 m3 s−1. This leads to a sediment bulking factor of 1.2 that corresponds to a flow with velocities similar to those of water during a flood.

scholarly journals Postglacial alluvial fan dynamics in the Cordillera Oriental, Peru, and palaeoclimatic implications

2018 ◽  
Vol 91 (1) ◽  
pp. 431-449 ◽  
Author(s):  
Kevin Ratnayaka ◽  
Ralf Hetzel ◽  
Jens Hornung ◽  
Andrea Hampel ◽  
Matthias Hinderer ◽  
...  
Keyword(s):  
Regional Climate ◽  
Transport Processes ◽  
Alluvial Fan ◽  
Alluvial Fans ◽  
Primary Control ◽  
Sediment Delivery ◽  
Data Set ◽  
Erosion Rates ◽  
History Of ◽  
Exposure Ages

AbstractAlluvial fans record climate-driven erosion and sediment-transport processes and allow reconstructing past environmental conditions. Here we investigate the sedimentation history of two alluvial fans located in formerly glaciated valleys of the Cordillera Oriental, Peru.10Be exposure ages from the fan surfaces and radiocarbon ages from the fan interiors constrain the final stages of fan formation. The10Be and14C ages cluster mainly between 13.3–9.3 ka and 11,500–9700 cal yr BP, respectively. Our age data set indicates that—after deglaciation—large amounts of fan sediment were deposited until ∼10 ka, when sedimentation rates declined rather abruptly. This pattern is supported by10Be erosion rates for the fan catchments, because under the assumption of constant erosion the time needed to erode the material stored in the fans significantly exceeds their age. Correlating our ages with regional climate records indicates that precipitation exerts the primary control on fan sedimentation. Two periods with elevated lake levels and increased precipitation between 18 and 14.5 ka and from 13 to 11.5 ka resulted in rapid deposition of large fan lobes. Subsequently, lower precipitation rates decreased erosion in the catchments and sediment delivery to the fans, which have remained largely inactive since ∼9.5 ka.

Alluvial Fan Alteration Due to Debris-Flow Deposition, Incision, and Channel Migration at Forest Falls, California

2021 ◽  
Vol 27 (1) ◽  
pp. 29-41
Author(s):  
Kerry Cato ◽  
Brett Goforth
Keyword(s):  
Debris Flow ◽  
Water Content ◽  
Debris Flows ◽  
Dynamic Instability ◽  
Debris Avalanche ◽  
Alluvial Fan ◽  
Multiple Sources ◽  
Sediment Delivery ◽  
Field Methods ◽  
San Bernardino Mountains

ABSTRACT Historical patterns of debris flows have been reconstructed at the town of Forest Falls in the San Bernardino Mountains using a variety of field methods (mapping flow events after occurrence, dendrochronology evidence, soil chronosequences). Large flow events occur when summer thunderstorms produce brief high-intensity rainfall to mobilize debris; however, the geomorphic system exhibits properties of non-linear response rather than being a single-event precipitation-driven process. Previous studies contrasted the relative water content of flows generated by varying-intensity summer thunderstorms to model factors controlling flow velocity and pathway of deposition. We hypothesize that sediment discharge in this geomorphic system exhibits multiple sources of complexity and present evidence of (1) thresholds of sediment delivery from sources at the higher reaches of bedrock canyons, (2) storage effects in sediment transport down the bedrock canyons, and (3) feedbacks in deposition, remobilization, and transport of sediment across the alluvial fan in dynamic channel filling, cutting, and avulsion processes. An example of the first component occurred in March 2017, when snowmelt generated a rapid translational landslide and debris avalanche of about 80,000 m3; this sediment was deposited in the bedrock canyon but moved no farther down gradient. The second component was observed when accumulation of meta-stable sediments in the bedrock canyon remained in place until fluvial erosion and subsequent debris flow provided dynamic instability to remobilize the mass downstream. The third component occurred on the alluvial fan below the bedrock canyon, where low-water-content debris flows deposited sediments that filled the active channel, raising the channel grade level to levee elevation, allowing for subsequent spread of non-channelized flows onto the fan surface and scouring new channel pathways down fan. A conceptual model of spatial and temporal complexities in this debris-flow system is proposed to guide future study for improved risk prediction.

Volume and Routing of Late-Glacial Runoff from the Southern Laurentide Ice Sheet

1990 ◽  
Vol 34 (1) ◽  
pp. 12-23 ◽  
Author(s):  
James T. Teller
Keyword(s):  
Gulf Of Mexico ◽  
Mississippi River ◽  
North Atlantic Ocean ◽  
Ice Sheet ◽  
Late Glacial ◽  
Laurentide Ice Sheet ◽  
Last Deglaciation ◽  
The North ◽  
Glacial Runoff ◽  
Southern Side

AbstractMelting of the Laurentide Ice Sheet during the last deglaciation added large volumes of water to many rivers and lakes of North America and to the world's oceans. The volume and routing of this meltwater not only helped shape the land's surface but also played a role in the evolution of late-glacial climate. A computerized model was prepared to quantify meltwater generation from seven drainage areas along the southern side of the Laurentide Ice Sheet at 500-yr time slices between 14,000 and 8000 yr B.P. Nearly all waters reaching the oceans flowed through the St. Lawrence, Hudson, or Mississippi River valleys. Discharge through the Mississippi River to the Gulf of Mexico during late-glacial time varied by more than a factor of 5, ranging between 17,400 m3 sec−1 (550 km3 yr−1) and 98,200 m3 sec−1 (3200 km3 yr−1). Discharge entering the North Atlantic Ocean through the St. Lawrence and Hudson valleys ranged between 20,300 m3 sec−1 (640 km3 yr−1) and 65,300 m3 sec−1 (2060 km3 yr−1), with very abrupt, twofold changes at about 11,000, 10,000, and 9500 yr B.P. as a result of the rerouting of water from the Lake Agassiz basin. As the areal extent and mass of the Laurentide Ice Sheet diminished, the total volume of meltwater plus runoff due to precipitation from its southern side declined from 3800 km3 yr−1 at about 14,000 yr B.P. to 2100 to 2600 km3 yr−1 between 11,500 and 8000 yr B.P. No meltwater entered the Gulf of Mexico after 9500 yr B.P. After the demise of the ice sheet over Hudson Bay about 8000 yr B.P., the modern continental drainage network was established and flows through the St. Lawrence declined to modern values of about 320 km3 yr−1.

Origin, development, and dynamics of coastal temperate conifer rainforests of southern Vancouver Island, Canada

2002 ◽  
Vol 32 (2) ◽  
pp. 353-372 ◽  
Author(s):  
K J Brown ◽  
R J Hebda
Keyword(s):  
Late Glacial ◽  
Vancouver Island ◽  
Tsuga Heterophylla ◽  
Fire Disturbance ◽  
Thuja Plicata ◽  
Quercus Garryana ◽  
Mixed Conifer Forests ◽  
Forested Ecosystems ◽  
Increasing Precipitation ◽  
Early Late

Pollen and charcoal from East Sooke Fen, Pixie Lake, and Whyac Lake were used to reconstruct the post glacial vegetation, climate, and fire-disturbance history across a precipitation gradient on southern Vancouver Island, British Columbia. An open Pinus woodland covered the landscape in the early late-glacial interval. Fires were absent under a cool and dry climate. Closed mixed conifer forests of Pinus, Picea, Abies, Tsuga heterophylla (Raf.) Sarg., and Tsuga mertensiana (Bong.) Carrière replaced the Pinus biogeochron in the late late-glacial interval. Fires became more common even though climate was cool and moist. Open Pseudotsuga menziesii (Mirb.) Franco forests expanded westward during the warm dry early Holocene, though closed Picea and Tsuga heterophylla forests grew in the wettest part of the area at Whyac Lake. Modern precipitation gradients likely originated at this time. Fires occurred in forested ecosystems, although East Sooke Fen at the driest end of the gradient experienced less fire. The middle and late Holocene was characterized by increasing precipitation and decreasing temperature, respectively. Quercus garryana Dougl. stands spread westward during the mid-Holocene. Extant closed Tsuga heterophylla and Cupressaceae (Thuja plicata Donn. ex D. Don) forests arose in the wetter part of the gradient, whereas Pseudotsuga forests occupied drier eastern areas. During this interval, fires were rare in wet western regions but apparently more common in dry eastern regions.

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