Předložený článek se zabývá výzkumem sedimentů nově vzniklého mrtvého ramene, které je lokalizová... more Předložený článek se zabývá výzkumem sedimentů nově vzniklého mrtvého ramene, které je lokalizováno v CHKO Poodří. Cílem studie je charakterizovat iniciální stadia jeho vývoje. Pro určení základních vlastností sedimentů byly použity metody vysokorozlišující stratigrafie. Byl změřen obsah vody, magnetická susceptibilita, spektrální odraznost ve viditelném světle, zrnitostní rozbor a obsah celkového organického uhlíku (TOC). Studované mrtvé rameno, situované u Polanky nad Odrou, bylo vytvořeno po povodních v roce 2010 protržením meandrové šíje. Na lokalitě byla odebrána dvě jádra o délce 81 cm (POD2) a 108 cm (POD1). Sedimenty sestávají převážně z prachu s vysokým podílem jílové frakce. Materiál s písčitou příměsí byl nalezen v bazálních částech, což nasvědčuje ukládání během iniciálního stadia vzniku mrtvého ramene. Magnetická susceptibilita a CIEL* vykazují určitou variabilitu, která je podmíněna změnami sedimentačních podmínek během roku. Zejména může indikovat jarní povodně a vyšš...
Riparian vegetation reflects the current conditions and the dynamics of streams. The floodplain v... more Riparian vegetation reflects the current conditions and the dynamics of streams. The floodplain vegetation along the watercourse of the Morávka River was subject to study in this project. In some reaches, the river has the natural character of an anabranching gravel-bed stream; in contrast, other Morávka R. reaches are incised into the bedrock. These cases were used to assess potential changes in vegetation conditions as evidence of negative processes taking place in the gravel-bed streams of the Beskydy Mts. The results demonstrate a higher biodiversity in the floodplain along the anabranching river channel. In contrast, the floodplain along the incised river channel shows low biodiversity values. Redundancy analysis was used to determine the relationships between plant species composition, distance from the main channel and relative elevation from the mean water level of the main channel. In addition, the results show a higher degree of change in plant species composition on the f...
The gently concave piedmont of the marginal slope of the Flysch Carpathians in the Czech Republic... more The gently concave piedmont of the marginal slope of the Flysch Carpathians in the Czech Republic has long been considered to comprise a system of pediments or coalescent alluvial fans. However, within one of the typical sections of this piedmont, large successive landslides with long travel distances of ~2.5 km have been identified through geophysical measurements and the investigation of an extensive artificial exposure. Accelerator mass spectrometry (AMS) radiocarbon dating and pollen analysis demonstrate that the uppermost generations of landslide deposits have originated since ~56 ka BP during the warmer and more humid interpleniglacial conditions of Marine Isotope Stage 3 (MIS 3). The geomorphological evidence for landsliding during MIS 3 has almost completely disappeared from this region due to intensive periglacial processes operating during the Last Glacial Maximum and subsequent fluvial and anthropogenic processes operating during the Holocene. The considerable antiquity of the studied terrestrial landslide bodies is unique within the context of Europe. This study shows the value of re-examining landscape development using new techniques and fresh exposures.
Landslides are important geomorphic agents in various mountainous settings. We document here a ca... more Landslides are important geomorphic agents in various mountainous settings. We document here a case of river piracy from the upper part of the Malá Brodská Valley in the Vsetínské Mts., Czech Republic (Rača Unit of the flysch Magura Group of Nappes, flysch belt of the Outer Western Carpathians) controlled by mass movement processes. Based on the field geological, geomorphological and geophysical data, we found out that the landslide accumulations pushed the more active river of out of two subparallel river channels with different erosion activity westwards and forced intensive lateral erosion towards the recently abandoned valley. Apart from the landslide processes, the presence of the N-striking fault, accentuated by higher flowrates of the eastern channel as a result of its larger catchment area,were the most critical factors of the river piracy. As a consequence of the river piracy, intensive retrograde erosion in the elbow of capture and also within the upper portion of the western catchment occurred. Deposits of two landslide dams document recent minimum erosion rates to be 18.8 mm.ky−1 in the western (captured) catchment, and 3.6 mm.ky−1 in the eastern catchment respectively. The maximum age of the river piracy is estimated to be of the late Glacial and/or the early Holocene.
Geomorphological impacts of extreme weather: Case studies from Central and Eastern Europe, Edition: Springer Geography, Chapter: 13, Publisher: Springer Verlag, Editors: Denes Loczy, pp.205-219, 2013
In May 2010 intensive rainfalls and consequent floods affected Central Europe, including the east... more In May 2010 intensive rainfalls and consequent floods affected Central Europe, including the eastern part of the Czech Republic. In the period 15–25 May 2010, more than 150 landslides originated in the Outer Western Carpathians and their foredeep. In the case of the Girová rockslide, the May 2010 rainfall event only supplied the final triggering push. The main preconditions of slope failure were long-term, internal changes within the rock mass. As evidenced by dendrogeomorphological dating, rock strength weakening was connected to long-term (decennial scale) creep leading to the final catastrophic movement. Many trees from the upper section of the landslide do not reveal any year of reaction wood. It could be explained by a translational, block-like character of movement.
Complex flow-like landslides (CFLLs) are important geomorphic agents of Late Quaternary mountain ... more Complex flow-like landslides (CFLLs) are important geomorphic agents of Late Quaternary mountain evolution in the Flysch Belt of the Outer Western Carpathians. The CFLLs are characterised by the upper section of deep-seated, retrogressive landslide of structurally unfavourably oriented rocks and lower sections composed of earthflows originated due to liquefaction of material accumulated from the upper slopes. Radiocarbon dating of organic matter incorporated into landslide debris or related deposits suggests that most of the CFLLs collapsed repeatedly throughout the Holocene with typical recurrence intervals of approximately 1–2 ka. Catastrophic landslides that occurred during extreme hydrometeorological events in recent decades displayed evidence of Holocene activity. Most of the CFLLs dammed and steepened adjacent valleys. Our chronological dataset is biased by erosion of older landforms, but most of the dated reactivations correlate to regional increases in humidity identified by previous paleoenvironmetal studies.
Large-scale ancient landslides of the area of more than 5 km2 and volume exceeding 200 × 106 m3 a... more Large-scale ancient landslides of the area of more than 5 km2 and volume exceeding 200 × 106 m3 are characteristic features of the valleys incised in the northern periphery of the Crimean Mountains (Ukraine). The largely affected area is located in the outermost cuesta range of the Crimean Mountains which consists of rigid Sarmatian limestones overlying weak Middle Miocene and Upper Palaeogene deposits. A giant landslide arose in the Alma water gap as a reflection of several coincident preparatory factors such as suitable bedrock stratification, smectite-rich bedrock exposed to swelling activity, presence of faults parallel to the valley trend, and river capture event which preceded the landslide event. The occurrence of such ancient megaslides is particularly interesting in the area which is characterized by low precipitation (<500 mm/year) and weak contemporary seismicity. It probably reflects a more dynamic environment in humid phases of the Holocene; however, seismic triggering along the Mesozoic suture zone cannot be rejected. Compressional features such as gravitational folds in the central and distal parts of the landslide, which probably correlate with the whole landslide genesis or its significant reactivation, arose, according to the radiocarbon dating, during the Holocene climatic optimum in the Atlantic period. The slope deformation has been relatively quiescent since that time, except minor historic reactivization which took place in the frontal part of the landslide. We suppose that the studied landslide could be classified as a transitional type of slope deformation with some signs of spreading and translational block slides.
Large-scale, low-gradient ancient landslides estimated at 5.4–18.9 km2 in area and ∼ 0.2–1.2 km3 ... more Large-scale, low-gradient ancient landslides estimated at 5.4–18.9 km2 in area and ∼ 0.2–1.2 km3 in volume have been studied in the northern hilly periphery of the Crimean Mountains (Ukraine). They originated on slopes along wide water gaps of rivers (Belbek, Kacha, Alma and Biyuk–Karasu) crossing the cuestas of the northern foothills. The slopes generally consist of slightly northward tilting Miocene (mainly Sarmatian) limestones overlying weak, clay-rich Lower Neogene–Palaeogene substratum with a significant content of smectite. Although the region is characterised by the least active contemporary morphodynamics within the Crimean Mountains, the landslides which were studied are of the same size or even larger than various types of landslides occupying active geomorphic domains of the highest mountain range in the southernmost part of the peninsula. The landslides are generally a spreading type, but the sliding mechanics were probably very complex, involving toppling, rotational slides, gravitational folding and translational block slides. All the landslides which were studied are located in the vicinity of regional faults and three of them have headscarps aligned along faults. A common feature is also a location close (within several km) to the Mesozoic suture zone which is the most important tectonic feature in the northern periphery of the Crimean Orogene. This suture was formerly classified as aseismic; however, evidence of strong, low-frequency palaeoearthquakes was collected during the last decade within both the Mesozoic suture and the low-lying northern part of the Crimean Peninsula. Radiocarbon dating of deposits associated with the landslides has revealed at least two phases of increased landslide-activity during the Late Glacial chronozone and Holocene epoch. The main landslide phase presumably took place at some time between the Late Glacial and Atlantic chronozones. Minor reactivation of landslide toes occurred during the Subatlantic chronozone and some of them have been active up to recent times. The first major landslide phase was possibly triggered by an earthquake, whereas late Holocene activity can be attributed both to seismic and hydroclimatic factors.
Deep-seated gravitational deformations are significant denudational agents of rock slopes at the ... more Deep-seated gravitational deformations are significant denudational agents of rock slopes at the margins of karstified plateaus of the Crimean Mountains (Ukraine). The aim of this article is to study long-term evolution of a giant rock slope failure close to the Black Sea coast in the southwestern tip of the mountains near Foros Town. The failure evolved in highly anisotropic limestones overlying plastic flysch layers where the main headscarp follows a strike-slip fault. We tested a new chronological strategy based on 14C and U-/Th-series dating of speleothems from unroofed caves exposed in the headscarp area of the slope failure. This approach made it possible to state maximum age of the slope collapse in individual parts of the deformed slope. Obtained results indicate that extension of discontinuities together with their karstification can be traced to > 300 ka BP, whereas evolution of the main headscarp started ~ 110 ka BP and since then it has propagated in the eastward direction. The youngest slope failure in the easternmost part of the studied collapse is of Late Holocene age. Our study indicates that conditions for large rock slope failures in carbonate areas can be prepared by speleogenesis or combined effects of propagation of cracks and their solution-based expansion. Furthermore, large rock slope failures can be important factors for the genesis of unroofed caves.
More than 150 landslides originated in the eastern part of the Czech Republic (region of the Flys... more More than 150 landslides originated in the eastern part of the Czech Republic (region of the Flysch Outer Western Carpathians - hereinafter, OWC) due to soil saturation caused by antecedent precipitation and long lasting and intensive rainfalls on 16–18 May 2010 (>300 mm as measured by some stations). As a consequence, a multitude of small failures originated 88% of which was smaller than 104 m2. Most landslides are characterised as shallow (<10 m) or middle–deep (10–30 m) incipient (rather short travel) landslides, debris slides and soil slips spatially clustered to a geological domain underlain by rather weak thin-bedded flysch and unconsolidated Quaternary deposits. An exception to this is represented by a kilometre-long rockslide (∼2–3 mil m3) affecting tectonically weakened and weathered claystone/mudstone-dominated flysch on the southern slope of Mt. Girová (the Beskydy Mountains). The rockslide is one of the largest long runout landslides in the territory of the Czech Republic activated over the past few decades as it reaches the dimensions of the largest documented Holocene long runout landslides in the Czech part of the OWC. A majority of the May 2010 landslide events developed inside older (Holocene or historic) landslide terrains, which points to their spatial persistency and recurrent nature. In spite of the fact that the May 2010 landslide event was not as destructive as some previous landslide activisation in the OWC region (e.g. July 1997 event), it left many slope failures at the initial stage of their potential future reactivation.
Předložený článek se zabývá výzkumem sedimentů nově vzniklého mrtvého ramene, které je lokalizová... more Předložený článek se zabývá výzkumem sedimentů nově vzniklého mrtvého ramene, které je lokalizováno v CHKO Poodří. Cílem studie je charakterizovat iniciální stadia jeho vývoje. Pro určení základních vlastností sedimentů byly použity metody vysokorozlišující stratigrafie. Byl změřen obsah vody, magnetická susceptibilita, spektrální odraznost ve viditelném světle, zrnitostní rozbor a obsah celkového organického uhlíku (TOC). Studované mrtvé rameno, situované u Polanky nad Odrou, bylo vytvořeno po povodních v roce 2010 protržením meandrové šíje. Na lokalitě byla odebrána dvě jádra o délce 81 cm (POD2) a 108 cm (POD1). Sedimenty sestávají převážně z prachu s vysokým podílem jílové frakce. Materiál s písčitou příměsí byl nalezen v bazálních částech, což nasvědčuje ukládání během iniciálního stadia vzniku mrtvého ramene. Magnetická susceptibilita a CIEL* vykazují určitou variabilitu, která je podmíněna změnami sedimentačních podmínek během roku. Zejména může indikovat jarní povodně a vyšš...
Riparian vegetation reflects the current conditions and the dynamics of streams. The floodplain v... more Riparian vegetation reflects the current conditions and the dynamics of streams. The floodplain vegetation along the watercourse of the Morávka River was subject to study in this project. In some reaches, the river has the natural character of an anabranching gravel-bed stream; in contrast, other Morávka R. reaches are incised into the bedrock. These cases were used to assess potential changes in vegetation conditions as evidence of negative processes taking place in the gravel-bed streams of the Beskydy Mts. The results demonstrate a higher biodiversity in the floodplain along the anabranching river channel. In contrast, the floodplain along the incised river channel shows low biodiversity values. Redundancy analysis was used to determine the relationships between plant species composition, distance from the main channel and relative elevation from the mean water level of the main channel. In addition, the results show a higher degree of change in plant species composition on the f...
The gently concave piedmont of the marginal slope of the Flysch Carpathians in the Czech Republic... more The gently concave piedmont of the marginal slope of the Flysch Carpathians in the Czech Republic has long been considered to comprise a system of pediments or coalescent alluvial fans. However, within one of the typical sections of this piedmont, large successive landslides with long travel distances of ~2.5 km have been identified through geophysical measurements and the investigation of an extensive artificial exposure. Accelerator mass spectrometry (AMS) radiocarbon dating and pollen analysis demonstrate that the uppermost generations of landslide deposits have originated since ~56 ka BP during the warmer and more humid interpleniglacial conditions of Marine Isotope Stage 3 (MIS 3). The geomorphological evidence for landsliding during MIS 3 has almost completely disappeared from this region due to intensive periglacial processes operating during the Last Glacial Maximum and subsequent fluvial and anthropogenic processes operating during the Holocene. The considerable antiquity of the studied terrestrial landslide bodies is unique within the context of Europe. This study shows the value of re-examining landscape development using new techniques and fresh exposures.
Landslides are important geomorphic agents in various mountainous settings. We document here a ca... more Landslides are important geomorphic agents in various mountainous settings. We document here a case of river piracy from the upper part of the Malá Brodská Valley in the Vsetínské Mts., Czech Republic (Rača Unit of the flysch Magura Group of Nappes, flysch belt of the Outer Western Carpathians) controlled by mass movement processes. Based on the field geological, geomorphological and geophysical data, we found out that the landslide accumulations pushed the more active river of out of two subparallel river channels with different erosion activity westwards and forced intensive lateral erosion towards the recently abandoned valley. Apart from the landslide processes, the presence of the N-striking fault, accentuated by higher flowrates of the eastern channel as a result of its larger catchment area,were the most critical factors of the river piracy. As a consequence of the river piracy, intensive retrograde erosion in the elbow of capture and also within the upper portion of the western catchment occurred. Deposits of two landslide dams document recent minimum erosion rates to be 18.8 mm.ky−1 in the western (captured) catchment, and 3.6 mm.ky−1 in the eastern catchment respectively. The maximum age of the river piracy is estimated to be of the late Glacial and/or the early Holocene.
Geomorphological impacts of extreme weather: Case studies from Central and Eastern Europe, Edition: Springer Geography, Chapter: 13, Publisher: Springer Verlag, Editors: Denes Loczy, pp.205-219, 2013
In May 2010 intensive rainfalls and consequent floods affected Central Europe, including the east... more In May 2010 intensive rainfalls and consequent floods affected Central Europe, including the eastern part of the Czech Republic. In the period 15–25 May 2010, more than 150 landslides originated in the Outer Western Carpathians and their foredeep. In the case of the Girová rockslide, the May 2010 rainfall event only supplied the final triggering push. The main preconditions of slope failure were long-term, internal changes within the rock mass. As evidenced by dendrogeomorphological dating, rock strength weakening was connected to long-term (decennial scale) creep leading to the final catastrophic movement. Many trees from the upper section of the landslide do not reveal any year of reaction wood. It could be explained by a translational, block-like character of movement.
Complex flow-like landslides (CFLLs) are important geomorphic agents of Late Quaternary mountain ... more Complex flow-like landslides (CFLLs) are important geomorphic agents of Late Quaternary mountain evolution in the Flysch Belt of the Outer Western Carpathians. The CFLLs are characterised by the upper section of deep-seated, retrogressive landslide of structurally unfavourably oriented rocks and lower sections composed of earthflows originated due to liquefaction of material accumulated from the upper slopes. Radiocarbon dating of organic matter incorporated into landslide debris or related deposits suggests that most of the CFLLs collapsed repeatedly throughout the Holocene with typical recurrence intervals of approximately 1–2 ka. Catastrophic landslides that occurred during extreme hydrometeorological events in recent decades displayed evidence of Holocene activity. Most of the CFLLs dammed and steepened adjacent valleys. Our chronological dataset is biased by erosion of older landforms, but most of the dated reactivations correlate to regional increases in humidity identified by previous paleoenvironmetal studies.
Large-scale ancient landslides of the area of more than 5 km2 and volume exceeding 200 × 106 m3 a... more Large-scale ancient landslides of the area of more than 5 km2 and volume exceeding 200 × 106 m3 are characteristic features of the valleys incised in the northern periphery of the Crimean Mountains (Ukraine). The largely affected area is located in the outermost cuesta range of the Crimean Mountains which consists of rigid Sarmatian limestones overlying weak Middle Miocene and Upper Palaeogene deposits. A giant landslide arose in the Alma water gap as a reflection of several coincident preparatory factors such as suitable bedrock stratification, smectite-rich bedrock exposed to swelling activity, presence of faults parallel to the valley trend, and river capture event which preceded the landslide event. The occurrence of such ancient megaslides is particularly interesting in the area which is characterized by low precipitation (<500 mm/year) and weak contemporary seismicity. It probably reflects a more dynamic environment in humid phases of the Holocene; however, seismic triggering along the Mesozoic suture zone cannot be rejected. Compressional features such as gravitational folds in the central and distal parts of the landslide, which probably correlate with the whole landslide genesis or its significant reactivation, arose, according to the radiocarbon dating, during the Holocene climatic optimum in the Atlantic period. The slope deformation has been relatively quiescent since that time, except minor historic reactivization which took place in the frontal part of the landslide. We suppose that the studied landslide could be classified as a transitional type of slope deformation with some signs of spreading and translational block slides.
Large-scale, low-gradient ancient landslides estimated at 5.4–18.9 km2 in area and ∼ 0.2–1.2 km3 ... more Large-scale, low-gradient ancient landslides estimated at 5.4–18.9 km2 in area and ∼ 0.2–1.2 km3 in volume have been studied in the northern hilly periphery of the Crimean Mountains (Ukraine). They originated on slopes along wide water gaps of rivers (Belbek, Kacha, Alma and Biyuk–Karasu) crossing the cuestas of the northern foothills. The slopes generally consist of slightly northward tilting Miocene (mainly Sarmatian) limestones overlying weak, clay-rich Lower Neogene–Palaeogene substratum with a significant content of smectite. Although the region is characterised by the least active contemporary morphodynamics within the Crimean Mountains, the landslides which were studied are of the same size or even larger than various types of landslides occupying active geomorphic domains of the highest mountain range in the southernmost part of the peninsula. The landslides are generally a spreading type, but the sliding mechanics were probably very complex, involving toppling, rotational slides, gravitational folding and translational block slides. All the landslides which were studied are located in the vicinity of regional faults and three of them have headscarps aligned along faults. A common feature is also a location close (within several km) to the Mesozoic suture zone which is the most important tectonic feature in the northern periphery of the Crimean Orogene. This suture was formerly classified as aseismic; however, evidence of strong, low-frequency palaeoearthquakes was collected during the last decade within both the Mesozoic suture and the low-lying northern part of the Crimean Peninsula. Radiocarbon dating of deposits associated with the landslides has revealed at least two phases of increased landslide-activity during the Late Glacial chronozone and Holocene epoch. The main landslide phase presumably took place at some time between the Late Glacial and Atlantic chronozones. Minor reactivation of landslide toes occurred during the Subatlantic chronozone and some of them have been active up to recent times. The first major landslide phase was possibly triggered by an earthquake, whereas late Holocene activity can be attributed both to seismic and hydroclimatic factors.
Deep-seated gravitational deformations are significant denudational agents of rock slopes at the ... more Deep-seated gravitational deformations are significant denudational agents of rock slopes at the margins of karstified plateaus of the Crimean Mountains (Ukraine). The aim of this article is to study long-term evolution of a giant rock slope failure close to the Black Sea coast in the southwestern tip of the mountains near Foros Town. The failure evolved in highly anisotropic limestones overlying plastic flysch layers where the main headscarp follows a strike-slip fault. We tested a new chronological strategy based on 14C and U-/Th-series dating of speleothems from unroofed caves exposed in the headscarp area of the slope failure. This approach made it possible to state maximum age of the slope collapse in individual parts of the deformed slope. Obtained results indicate that extension of discontinuities together with their karstification can be traced to > 300 ka BP, whereas evolution of the main headscarp started ~ 110 ka BP and since then it has propagated in the eastward direction. The youngest slope failure in the easternmost part of the studied collapse is of Late Holocene age. Our study indicates that conditions for large rock slope failures in carbonate areas can be prepared by speleogenesis or combined effects of propagation of cracks and their solution-based expansion. Furthermore, large rock slope failures can be important factors for the genesis of unroofed caves.
More than 150 landslides originated in the eastern part of the Czech Republic (region of the Flys... more More than 150 landslides originated in the eastern part of the Czech Republic (region of the Flysch Outer Western Carpathians - hereinafter, OWC) due to soil saturation caused by antecedent precipitation and long lasting and intensive rainfalls on 16–18 May 2010 (>300 mm as measured by some stations). As a consequence, a multitude of small failures originated 88% of which was smaller than 104 m2. Most landslides are characterised as shallow (<10 m) or middle–deep (10–30 m) incipient (rather short travel) landslides, debris slides and soil slips spatially clustered to a geological domain underlain by rather weak thin-bedded flysch and unconsolidated Quaternary deposits. An exception to this is represented by a kilometre-long rockslide (∼2–3 mil m3) affecting tectonically weakened and weathered claystone/mudstone-dominated flysch on the southern slope of Mt. Girová (the Beskydy Mountains). The rockslide is one of the largest long runout landslides in the territory of the Czech Republic activated over the past few decades as it reaches the dimensions of the largest documented Holocene long runout landslides in the Czech part of the OWC. A majority of the May 2010 landslide events developed inside older (Holocene or historic) landslide terrains, which points to their spatial persistency and recurrent nature. In spite of the fact that the May 2010 landslide event was not as destructive as some previous landslide activisation in the OWC region (e.g. July 1997 event), it left many slope failures at the initial stage of their potential future reactivation.
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