Evolution of fluvial environments and history of human settlements on the Ticino river alluvial plain

The present contribution aims to provide better knowledge on the evolution of the fluvial environments of the Ticino river alluvial plain, highlighting the complex interaction of the Ticino river and its lateral tributaries with the human communities since the Neolithic. The study considers information derived from historical sources, from previous research on three sites based in the Ticino river floodplain and from data of six archaeological sites located on four alluvial fans. For the investigated sites the analyses of the lithostratigraphy and the archaeological evidence were constrained with radiocarbon dating, providing the interpretation of the depositional context of the studied sequences and their correlation with the cultural periods and epochs defined for the southern Swiss Alps. The combined approach allowed for the definition of 13 phases of enhanced hydro-sedimentary activity from the Neolithic to the contemporary period. The possible palaeoenvironmental and palaeoclimatic causes, as well as the impacts of these phases on the human settlements, are discussed.

Control of glacial and fluvial environments in the Ny-Alesund region, Arctic

Ny-Alesund, located in Svalbard, Arctic exhibits complex topography and geomorphic features evolved by various sedimentary environments under direct control of climate and tectonics. The controls of glacial and fluvial environments were analyzed on the basis of field documentation of geomorphic features evolved by small valley glaciers (Vestre brogger and Midre loven) and streams originating from it. These terrestrial valley glaciers are characterized by convex wrinkled surface, crevasses, bergchrunds, supraglacial streams, longitudinal debris strips, lateral moraines, recessional moraines, hummocky moraines, thrust moraines, convex longitudinal profile with breaks in slope, fractures and joints. The glacial deposits are made up of very poorly sorted clast to matrix supported boulders with varying sizes of clast, matrix and gravels. The matrix supported facies underlain by clast supported facies indicate the increasing energy of the glacier and so the cold climate. The bi-modal palaeocurrent pattern of moraines suggests two prominent directions for the movement of glaciers in the past under direct control of tectonic activity. The granulometric analysis of the streams indicate moderately sorted medium to coarse sand. The mean grain size decreases from origin to the middle reaches of the river and increases towards its mouth. The percentage of the finer sediments decreases and coarser fragments increases in the downstream direction. The results of the granulometric parameters which are contrary to the normal fluvial system are due to the control of tectonic activity. The present study provides the basic characteristics and activity of the glacial and fluvial environments the interpretation of, which explains the control of tectonic activity in this region.

The Potential Role of S-and Fe-Cycling Bacteria on the Formation of Fe-Bearing Mineral (Pyrite and Vivianite) in Alluvial Sediments from the Upper Chicamocha River Basin, Colombia

S- and Fe-cycling bacteria can decisively affect the crystallization of Fe-bearing minerals in sediments from fluvial environments. We have studied the relationships between the Fe-bearing mineral assemblage and the bacterial community composition in the sediments rich in organic matter from the upper Chicamocha river basin (Colombia). Rapid flowing sections of the river contain sediments that have a high redox potential, are poor in organic matter and are enriched in kaolinite and quartz. On the other hand, the mineral assemblage of the sediments deposited in the La Playa dam with a high content in organic matter is enriched in Fe-bearing minerals: a) vivianite and pyrite in the permanently flooded sediments of the dam and b) pyrite and goethite in the periodically emerged sediments. The bacterial community composition of these sediments reveals anthropic organic matter pollution processes and biodegradation associated with eutrophication. Moreover, periodically emerged sediments in the La Playa dam contain bacterial groups adapted to the alternation of dry and wet periods under oxic or anoxic conditions. Cell-shaped aggregates with a pyritic composition suggest that sulfate-reducing bacteria (SRB) communities were involved in the precipitation of Fe-sulfides. The precipitation of vivianite in the flooded sediments was favored by a greater availability of Fe(II), which promoted the iron-reducing bacteria (IRB) enrichment of the sediments. The presence of sulfur-oxidizing bacteria (SOB) in the flooded sediments and the activity of iron-oxidizing bacteria (IOB) in the periodically emerged sediments favored both pyrite crystallization under a high sulfide availability and the oxidation of microbially precipitated monosulfides. Moreover, IOB enhanced goethite formation in the periodically emerged sediments.

Automatic Features Detection in a Fluvial Environment through Machine Learning Techniques Based on UAVs Multispectral Data

The present work aims to demonstrate how machine learning (ML) techniques can be used for automatic feature detection and extraction in fluvial environments. The use of photogrammetry and machine learning algorithms has improved the understanding of both environmental and anthropic issues. The developed methodology was applied considering the acquisition of multiple photogrammetric images thanks to unmanned aerial vehicles (UAV) carrying multispectral cameras. These surveys were carried out in the Salbertrand area, along the Dora Riparia River, situated in Piedmont (Italy). The authors developed an algorithm able to identify and detect the water table contour concerning the landed areas: the automatic classification in ML found a valid identification of different patterns (water, gravel bars, vegetation, and ground classes) in specific hydraulic and geomatics conditions. Indeed, the RE+NIR data gave us a sharp rise in terms of accuracy by about 11% and 13.5% of F1-score average values in the testing point clouds compared to RGB data. The obtained results about the automatic classification led us to define a new procedure with precise validity conditions.

The Potential Use of Osl Properties of Quartz in Investigating Fluvial Processes on the Catchment of River Mureş, Romania

To understand the functioning of fluvial systems it is important to investigate dynamics of sediment transport and the source of sediments. In case of reconstructing past processes these studies must be accompanied by the numerical dating of sediment samples. In this respect optically stimulated luminescence is a widely used technique, by which the time of sediment deposition can be directly dated. Recently, in various fluvial environments it has been shown that certain luminescence properties of minerals, and especially that of quartz, can be applied as indicators of fluvial erosion and/or sediment provenance. These properties are residual luminescence (or residual dose) and luminescence sensitivity of quartz grains. However, the values of the parameters above are affected by various factors, the importance of which is under debate. The present study therefore aims to assess these factors along a ~560 km long reach of River Mureş (Maros) a relatively large river with a compound surface lithology on its catchment. The research focused on the sandy fraction of modern sediments, collected from the main river and from three tributaries alike. This way not only longitudinal downstream changes, but the influence of tributaries could also be studied. Based on the data, both investigated parameters show a great variation, which can be attributed to the lithological differences of subcatchments and geomorphological drivers, such as erosional activity and potential number of sedimentary cycles, and human activity. However, relationships are not entirely clear and are influenced by the maximum grain size of the samples investigated, and the recycling of previously laid deposits with different properties. Still, when performing detailed dating studies, and tracing sediments from certain parts of the catchment luminescence properties can be a useful tool in the future.

Morphodynamic stability and characteristic length scales of bifurcations and confluences loops

<p>The morphodynamics of multi-thread fluvial environments like braided and anastomosing rivers is fundamentally driven by the continuous concatenation of channel bifurcations and confluences, which govern the distribution of flow and sediment among the different branches that are reconnecting further downstream. Almost all studies performed to date consider the two processes separately, although they frequently appear as closely interconnected. In this work, we tackle the problem of analyzing the coupled morphodynamics of such bifurcation-confluence systems by studying the equilibrium and stability conditions of a channel loop, where flow splits into two secondary anabranches that rejoin after a prescribed distance. Through the formulation of a novel theoretical model for erodible bed confluences based on the momentum balance on two distinct control volumes, we show that the dominating anabranch (i.e. that carrying more water and sediment) is subject to an increase of the water surface elevation that is proportional to the square of the Froude number. This increase in water surface elevation tends to reduce the slope of the dominating branch, which produces a negative feedback that tends to stabilize the bifurcation-confluence system. A linear analysis of the coupled model reveals that the stabilizing effect of the confluence depends on the ratio between the length of the connecting channels and the average water depth, independently of the channel slope and Froude number. Furthermore, the effect of the confluence is potentially able to stabilize the channel loop in conditions where the classic stabilizing mechanism at the bifurcation (i.e. the topographical effect related to the gravitational pull on the sediment transport) is very weak, as expected when most of the sediment is transported in suspension. The identification of a characteristic length scale that produces a coupling between the confluences and bifurcations opens intriguing possibilities for interpreting the self-adjustment of the planform scale of natural multi-thread rivers.</p>

Unified model of sediment transport threshold and rate across subaqueous bedload, windblown sand, and windblown snow

<p>Nonsuspended sediment transport (NST) refers to the sediment transport regime in which the flow turbulence is unable to support the weight of transported grains. It occurs in fluvial environments (i.e., driven by a stream of liquid) and in aeolian environments (i.e., wind-blown) and plays a key role in shaping sedimentary landscapes of planetary bodies. NST is a highly fluctuating physical process because of turbulence, surface inhomogeneities, and variations of grain size and shape and packing geometry. Furthermore, the energy of transported grains varies strongly due to variations of their flow exposure duration since their entrainment from the bed. In spite of such variability, we here propose a deterministic model that represents the entire grain motion, including grains that roll and/or slide along the bed, by a periodic saltation motion with rebound laws that describe an average rebound of a grain after colliding with the bed. The model simultaneously captures laboratory and field measurements and discrete element method (DEM)-based numerical simulations of the threshold and rate of equilibrium NST within a factor of about 2, unifying weak and intense transport conditions in oil, water, and air (oil only for threshold). The model parameters have not been adjusted to these measurements but determined from independent data sets. Recent DEM-based numerical simulations (Comola, Gaume, et al., 2019, https://doi.org/10.1029/2019GL082195) suggest that equilibrium aeolian NST on Earth is insensitive to the strength of cohesive bonds between bed grains. Consistently, the model captures cohesive windblown sand and windblown snow conditions despite not explicitly accounting for cohesion.</p>

Microplastic in fluvial environments - an example of the Elbe river near Dessau-Roßlau, Germany

<p>Accumulation of microplastics (MPs) in aquatic environments is an issue of emerging concern. After research initially focused on marine systems, more and more studies have been published investigating the abundance of MPs in freshwater environments in recent years.</p><p>The objective of our research is to examine, whether the Mulde river represents an input pathway for MP particles to the Elbe discharge system. Our hypothesis is that the chemical industries located in the catchment area of the Mulde act as a discharge source of primary MPs which are subsequently transported downstream towards the Elbe. Accordingly, there should be more (primary) MPs just downstream of the river mouth, compared to upstream. Therefore, 2 sediment samples and 18 water samples from the Elbe river upstream and downstream the Mulde confluence were taken and analysed on their MP contents.</p><p>To extract MPs, sample preparation requires various steps including drying, size-fractionation, reduction of organic matter and density separation. The gained fractions are then filtered through glass microfibres paper using a vacuum pump. The dried filters are photographed and examined for MPs under a digital microscope. Representative particles are picked and measured. Finally, we determine their polymer type by pyrolysis or µFTIR.</p><p>A key result is that both, sediment and water samples, show a substantial increase in primary MPs (especially spheres) just downstream the mouth of the Mulde. Regarding the sampling technique of water samples, we observe differences in the amount and shape of MP particles between filter cascades and filter nets.</p>

Early human occupations in NW Iberia: The archaeological record of the Lower Miño basin during the second half of the Middle Pleistocene

The Miño River is one of the main Atlantic basins of Iberia and preserves extensive Pleistocene deposits. However, there is presently limited information concerning the first human occupation history of this region. Existing research undertaken across the region has identified a significant number of Large Flake Acheulean (LFA) sites with African affinities. These sites are associated with former fluvial environments and are now preserved as a sequence of fluvial terraces along the Miño River, located between relative elevations of + 40 m and + 20 m, and dated to between Marine Isotope Stages (MIS) 9 and 6. The chronological range and observed technological patterns are similar to those recognised in other areas of South western Europe, particularly the central Iberian Peninsula and Aquitanian region (France) during the second half of the Middle Pleistocene.