Reconstruction of Nineteenth-Century Channel Patterns of Polish Carpathians Rivers from the Galicia and Bucovina Map (1861–1864)

Historical maps are often the only source of information allowing for the regional reconstructions of river channel patterns in the past. In the Polish Carpathians, analyses of historical channel patterns were performed mostly in river reaches scale. In this paper, the Galicia and Bucovina map (1861–1864) (the Second military survey of the Habsburg Empire) was used to reconstruct and map the historical channel patterns of seven rivers from the Polish Carpathians. It was found that, in the nineteenth century, rivers in the western part of the study area (Soła, Skawa, Raba, Dunajec) supported a multi-thread channel pattern, whereas rivers in the eastern part (Wisłoka, San, Wisłok) present a mostly single-thread channel pattern. These differences probably result from the higher relief energy and precipitation, lower proportions of forests in the catchments, and more frequent floods favouring high sediment supply to the fluvial system, and thus the formation of multi-thread reaches in the western part of the study area. At the local scale, the most important factor supporting multi-thread channel pattern development was the availability of gravel sediments in the wide valley floor sections. The formation of anabranching reaches with a single mid-channel form was probably associated with the channel avulsion process. There is no clear evidence linking the change in the channel pattern type with an abrupt change in the river channel slope. This study confirms the usefulness of the second military survey map of the Habsburg Empire for the regional reconstruction of river channel pattern types.

The Impacts of Humans on Geomorphology

This chapter discusses the factors that have led to an increasing interest in the human impact in geomorphology, and then discusses the literature that appeared between c 1960 and 2000. These developments were in four main areas: (i) intellectual and policy-related (ii) technological developments that alter geomorphological processes (iii) demographic trends, and (iv) proliferation of techniques for the study of landform and process change. Much work was undertaken on landforms produced by construction and excavation. Interest also developed in accelerating ground subsidence, which is a widespread phenomenon that creates engineering problems. Indeed, with increasing exploitation of tundra areas for such activities as oil exploitation, there was an increasing interest in the problems associated with permafrost. Rivers have also been greatly impacted. Humans have modified sediment transport by rivers in two ways. First, as a result of accelerated soil erosion, the delivery of sediment to rivers has increased. Secondly, burgeoning dam construction has caused sediment to be trapped in reservoirs. Far-reaching changes in channel form have been produced by land-use and land-cover changes. In addition to non-deliberate changes to river systems, there have been a whole range of deliberate modifications (e.g. channelization). Some valley bottoms areas have suffered from accelerated sedimentation while others have become incised with gullies (arroyos). Studies have indicated an increasing incidence of mass movements. These have been attributed to such factors as deforestation, road cuts, changes in slope drainage and irrigation of farm land. Much work has also been undertaken on wind erosion of dryland surfaces. Human activities, most notably air pollution, have changed the nature and rate of weathering, though enhanced weathering by salt can also be accelerated by irrigation. Large numbers of people live in coastal zones and have had a major impact on coastal landforms and processes. Many of the world's shorelines have been eroding and the complex mix of causes, natural and anthropogenic, that could be responsible have been analysed. Finally, since the 1980s there has been a growing realisation of the importance of global heating for geomorphological phenomena.

Morphodynamic styles: characterising the behaviour of gravel-bed rivers using a novel, quantitative index

The assessment of channels widely focusses on using channel form to identify channel character, but fail to capture the more nuanced variations of morphodynamics without the analysis of process. This paper presents a method using an index of channel behaviour, the throughput ratio (ζ), which is calculated from morphologic change and sediment transport, and explores the viability of inferring process from channel form to act as an indicator of channel behaviour. Two experiments using the same initial width, slope, discharge and grain size were used to demonstrate the effectiveness of this method in representing different morphodynamics. In one experiment the channel was allowed to laterally deform, whilst the other had unerodible elements placed at its boundaries. As a result the experiment with mobile banks widened and reduced sediment transport to zero, whereas the fixed bank experiment— unable to decrease its shear stress— continued to output material. In both, the rate of morphologic change tended to zero despite their marked differences in sediment transport over time. The differences in evolution are due to the differences in process available to each channel despite a starting similarity in bed mobility and their gross similarity in a meandering planform. The throughput ratio allows new representations of the temporal and spatial patterns of the morphodynamics, providing additional measures with which to analyse the processes acting in river channels.

Application of equilibrium theory on alluvial channel-form adjustment in a large river heavily loaded with sediment

<p>Taking the width/depth ratio of an alluvial channel as an independent variable, a variational analysis of basic flow relationships shows that flow is able to achieve stationary equilibrium by adjusting channel geometry when the condition of maximum flow efficiency (MFE) is satisfied. To examine if this theory of self-adjusting channel morphodynamics can be practically applied to large river systems heavily loaded with sediment, this study examines the degree of correspondence between theoretically determined equilibrium channel geometries and actual measurements along the lower Yellow River. Using the Meyer-Peter and Müller bedload relation <span>modified</span><span> </span><span>on the basis of MFE theory and relations of flow continuity and resistance we present a detailed investigation of the potential physical causes and main factors resulting in the correspondence. </span></p>

Linking Hydrologic and Hydraulic Data with Models to Assess Flow and Channel Alteration at Hog Park, Wyoming USA

Transbasin diversions and dams allow for water uses when and where there is high demand and low supply, but can come with an expense to the environment. This paper presents a linkage of hydrologic and hydraulic modeling and datasets to assess the hydrologic and hydraulic stability within a transbasin watershed as an approach for meeting water use targets and safeguarding environmental sustainability. The approach used a Prediction in Ungauged Basin (PUB) regionalization technique that completed the parameterization of a study watershed hydrologic model by transferring calibrated parameters from a reference watershed hydrologic model. This resulted in a long-term, simulated natural flow record that was compared to the measured modified flow record for the same time period to assess flow alteration. In the sensitive reach, hydraulic modeling results tracked channel response from before hydrologic modification to baseline using repeated survey years during the hydrologic modification. The combined assessment of hydrology and hydraulics highlighted the relation between flow regime and channel form.

Channel-levee evolution in combined contour current–turbidity current flows from flume-tank experiments

Turbidity currents and contour currents are common sedimentary and oceanographic processes in deep-marine settings that affect continental margins worldwide. Their simultaneous interaction can form asymmetric and unidirectionally migrating channels, which can lead to opposite interpretations of paleocontour current direction: channels migrating against the contour current or in the direction of the contour current. In this study, we performed three-dimensional flume-tank experiments of the synchronous interaction between contour currents and turbidity currents to understand the effect of these combined currents on channel architecture and evolution. Our results show that contour currents with a velocity of 10–19 cm s−1 can substantially deflect the direction of turbidity currents with a maximum velocity of 76–96 cm s−1, and modify the channel-levee system architecture. A lateral and nearly stationary front formed on the levee located upstream of the contour current, reduced overspill and thus restrained the development of a levee on this side of the channel. Sediment was preferentially carried out of the channel at the flank located downstream of the contour current. An increase in contour-current velocity resulted in an increase in channel-levee asymmetry, with the development of a wider levee and more abundant bedforms downstream of the contour current. This asymmetric deposition along the channel suggests that the direction of long-term migration of the channel form should go against the direction of the contour current due to levee growth downstream of the contour current, in agreement with one of the previously proposed conceptual models.