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EN
Differentiation of groundwater flow conditions within the floodplains of the river valleys in the Polish Lowlands may result from polygenesis of their valleys sections, as well as from the evolution of river systems, which lasts from the end of the Pleistocene. The investigations, which were carried out in the middle Vistula valley showed that important factor for differentiation of groundwater flow conditions within the floodplain could be also the influence of the basement of contemporary alluvia. In the sections where it forms morphological protrusions, the basement affects the flood waters flow which transforms upper part of floodplain lithological profile.
PL
W dolinach rzecznych na Niżu Polskim powszechnie stwierdzanym zjawiskiem jest występowanie w strefie korytowej kulminacji podłoża aluwiów zbudowanych z utworów trudno rozmywanych. Formy te pełnią rolę lokalnych baz erozyjnych i stabilizują profil podłużny koryta. Jak dowodzą badania prowadzone w dolinie Wisły środkowej, kulminacje podłoża aluwiów wpływają także na działalność wód wezbraniowych. W miejscach ich występowania na powierzchni tarasu zalewowego znajdują się charakterystyczne formy erozyjne i akumulacyjne związane z przepływem wielkich wód. W obrębie analizowanego w pracy odcinka doliny Pilicy, w okolicach Inowłodza, stwierdzono występowanie trudno rozmywanych progów zbudowanych z piaskowców jurajskich, utworów morenowych i rezydualnych bruków. Blokowanie przepływu wielkich wód przez te formy było przyczyną charakterystycznego przeobrażenia powierzchni tarasu zalewowego.
EN
Within the channel zone of the of Polish Lowland river valleys the protrusions of alluvial basement, composed of erosion resistant deposits occur. These forms act as erosion bases, stabilized longitudinal profile of river valley. In the Middle Vistula River valley, protrusions induce the concentration of high water flow, as well as mean waters flow. As the result of this phenomenon there are flood water erosion troughs on the surface of the flood plain, as well as high water alluvial fans. Those forms can be utilized as indicators pointing out the protrusion zones. In the analyzed Pilica River Valley reach in the vicinity of Inowłódz there are protrusions composed of Jurassic sandstones, moraine cohesive soils, as well as residual lags. Constraint of the flood waters is the reason of remodeling of upper part of Holocene alluvial plain.
PL
Badania prowadzone w dolinie Wisły środkowej wykazały występowanie w jej strefie korytowej kulminacji podłoża aluwiów, zbudowanych z utworów o większej odporności na erozję. Na odcinku przełomu Wisły są to grunty skaliste, głównie kredy i paleogenu, a poniżej niego grunty nieskaliste paleogenu i neogenu (w tym także różnorodne utwory glacjalne). Utwory kenozoiku są często zaburzone glacitektonicznie. Na powierzchni tych osadów występują powszechnie rezydualne bruki zbudowane ze żwirów i otoczaków. Ich obecność świadczy o odsłanianiu powierzchni kulminacji w czasie przepływu wielkich wód. Morfologia podłoża aluwiów wpływa wtedy na koncentrację strumienia wód rzeki. Zjawisko to przed wybudowaniem wałów objawiało się różnicowaniem stref erozji i depozycji wezbraniowej na powierzchni tarasu zalewowego, a obecnie jest przyczyną powtarzających się awarii budowli regulacyjnych.
EN
Investigations within the channel zone of the Middle Vistula River have shown the presence of culminations of the basement composed of deposits resistant to erosion. On their surface in the bottom part of the present-day channel facies occur residual lags built of gravels and pebbles. They point to the exposure of the surface of the alluvial basement in the channel bottom during high-waters. Culminations of the resistant alluvial basement often reveal a complex morphology which influences the course of the main channel, particularly during high-water stages. The stable trend to concentrate the high-water stream may be the reason of the damage of regulating and flood control system structures. The influence of the basement on the concentration of the high-water flow may also induce the formation of specific erosional and depositional forms on the terrace surface. Such forms can thus serve as indicators of these zones. The paper presents examples of three reaches from the analysed 250-km fragment of the Middle Vistula River Valley.
EN
Investigations within the channel zone of the Middle Vistula River have shown the presence of protrusions of the alluvial basement composed of deposits resistant to erosion. On their surface, and in the basal part of the present-day channel facies, occur residual lags composed of gravels and pebbles. These lags indicate exposure of the surface of the alluvial basement in the channel bottom during high-water stages. Protrusions of the resistant alluvial basement often show a complex morphology which influences the course of the thalweg, particularly during floods. The constant trend to concentrate the high-water stream may be the reason for the damage to regulation and flood control system structures. The concentration of the high-water flow causes the formation of specific erosional and depositional forms on the terrace surface. Such forms can thus serve as indicators of the zones of alluvial basement protrusions. The paper presents examples of three reaches of the Middle Vistula River Valley (The Mid-Polish Lowlands).
EN
Because of large amount of deposited material and the varied discharge of water, the Middle Vistula possesses the morphologic and lithological characteristics of braided river. During a geological survey of the valley which holds the bed of the Vistula River, culminations of the alluvia basement was detected in channel zone. There were outcrops of Mesozoic rocks — gaizes, marls and limestones, Paleogene and Neogene sediments as clays and sands and Pleistocene sediments as boulder clays, ice-dam deposits and compressed coarse grains fluvioglacial sediments are occasionally found. On the surface of these structures, the presence of residual lags was detected. The shallow location of these types of structures in the river channel proves its erosion-resistant nature. In long section of river bottom they are marked by a considerable increase of their gradient. Resistant steps of this kind are crucial for the natural stability of the river valley in longi-tudinal profile. They can also cause culmination of flood flows. The presence of the culminations of the alluvia basement in the river channel may be a factor increasing the probability of ice jam formation and ice jam floods. Those phenomena are causes of characteristic morphology of terrace surface — presence of erosional troughs of flood event flows. They also affect depositional processes. In the paper the morphologic characteristics of the Middle Vistula (braided lowland river) in the zones of various lithological types of alluvial basement culminations are presented, as well as characteristic structures of channel and flood deposits.
6
Content available remote Wpływ podłoża aluwiów na morfologię koryta Wisły w rejonie Góry Kalwarii
EN
The investigations, carried out in the Vistula river valley near Góra Kalwaria (Vistula middle course) were focused on the estimation of connections between alluvial basement position and contemporary channel stability. The culmination of basement was discovered in the upper part of the studied reach. It is generally composed of fluvioglacial deposits, covered by coarse-grained residuum residual lag. The occurence of this culmination has an effect on the position of the main channel during high water states, as well as lateral erosion and stability of channel depositional forms.
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