Sediment Control At The Lateral Channel Inlet

Environmental and civil engineering projects frequently employ the open channel side intake structure. However, the commonest among the issues faced in most of the lateral intakes include sedimentation and sediment delivery. This involves several problems namely, decreased flow discharge capacity in the irrigation canals and the threat of water blockage during times of low water flow. Besides, this problem with the sediment either lowers the performance levels or causes failure of the facilities that this sub-channel serves. Hence, the engineers focused on designing an intake with the features of high flow discharge and low sediment delivery. This paper attempts to review and summarize the literature relevant to the branching channel flow and submerged vane technique to minimize the sediment-related issues. The present review highlights that most of the earlier research work done dealt with the characteristics of the flow in a right-angle branch channel possessing rigid confines. Also, more investigations are required regarding the implications of the submerged vanes. Besides, no comprehensive studies are available on the saddle point itself, and a high percentage of the studies have been part of earlier investigations that had focused on only briefly outlining this subject.

TAPHONOMY AND DEPOSITIONAL SETTING OF THE SHRINGASAURUS INDICUS (ARCHOSAUROMORPHA: ALLOKOTOSAURIA) BONEBED FROM THE MIDDLE TRIASSIC DENWA FORMATION, SATPURA GONDWANA BASIN, INDIA

ABSTRACT A bonebed of multiple skeletons of the Triassic horned reptile Shringasaurus indicus was discovered in the upper Denwa Formation, Satpura Gondwana Basin, India. The monotaxic bonebed contains multiple individuals of different ontogenic stages indicating herding behavior by Shringasaurus indicus. The herd was a mixed-sex herd. The adult and sub-adult bones in the bonebed exceed the number of juvenile bones. The distribution of the bones was slightly patchy, bones of different individuals were admixed, and several bones were piled up implying mass mortality. The bonebed occurs in a fine-grained mudrock that is hydraulically incompatible with long-distance transport and concentration by currents. Sedimentary facies analysis indicates that the bonebed accumulated and was buried in a crevasse splay deposit between two ENE-WSW trending channel-fill complexes. The northern channel-fill complex was formed by unidirectional flow with lateral channel migration towards the south and with minor contemporaneous tectonic subsidence. Repeated breaching of the levee by this channel flow led to the incremental development of the crevasse splay deposit. The herd of Shringasaurus indicus, which lived near to the perennial channel, was drowned en masse and the carcasses were trapped within the muddy sediments of the crevasse splay deposit. Apart from a partially articulated skeleton, the rest of the bones were disarticulated but remained associated. The bones show little evidence of post-mortem modifications. With a continuous supply of the sediments through the spillover channels, the bones were buried before complete disarticulation and dispersal had taken place.

Coarse-grained meandering distributive fluvial system of the basal Cedar Mountain Formation, U.S.A.

ABSTRACT The analysis of downstream changes in ancient fluvial systems can better inform depositional models for foreland-basin systems. Herein we analyze the basal deposits of the Early Cretaceous Cedar Mountain Formation of Utah to better understand the variety of fluvial deposits present and to develop a depositional model for the Sevier foreland basin. We also evaluate the long-held interpretation of a braided origin for these deposits and document numerous examples of point-bar deposition in highly sinuous meandering rivers by analysis of large (20 to 60 km2) plan-view exposures. These plan-view exposures allow comparisons between planform and cross-sectional geometries. The study utilizes outcrop data, virtual outcrop models, and satellite imagery to develop a facies model and analyze the architecture of channel bodies in the Buckhorn Conglomerate and Poison Strip Sandstone of the Cedar Mountain Formation. We document downstream (west to east) decreases in lateral channel migration, sinuosity, channel amalgamation, grain size, and percent of fluvial channel facies (conglomerate and sandstone). Fluvial channel deposits occur arranged into larger stratal bodies: multistory–multilateral channel bodies that are dominantly composed of clast-supported conglomerate in the west to a mix of multistory, multilateral, and isolated channel bodies composed of matrix-supported conglomerate in the east. The median width of highly sinuous point bars is similar across the field area (344 m to 477 m), but the inclusion of narrower (median = 174 m), low-sinuosity bar elements in the east indicates an overall reduction in lateral channel migration and sinuosity downstream. Net-to-gross values range from 100% in much of the western outcrops to as low as 38% in the east. Paleocurrent analysis reveals a transverse (west to east) paleoflow for the study interval that merges with axial (south–north) paleoflow near the Utah–Colorado state line. We estimate 104 m3/s-scale discharge and 106 kilometer-scale drainage area for axial rivers based on paleohydraulic analysis which represents a significant part of the Early Cretaceous continental-scale drainage. The observed downstream trends in lateral channel migration, sinuosity, channel amalgamation, grain size, and net-to-gross for the basal Cedar Mountain Formation are consistent with expected trends for sinuous single-thread distributive fluvial systems and are similar to observed trends in the Jurassic Morrison Formation. Medial (Buckhorn Conglomerate) to distal (Poison Strip Sandstone) zones are preserved and span the forebulge to backbulge depozones of a foreland-basin system. Postulated deposits of the proximal distributive fluvial system have been removed during erosion of the foredeep depozone. The easternmost Poison Strip Sandstone and coeval Burro Canyon Formation represent deposits of an axial system at which western-sourced distributive fluvial systems end. Distributive fluvial systems dominate modern foreland basins, and this study suggests that they may constitute a significant proportion of ancient successions.

RIVERBED, BANKS AND BEYOND: AN EXAMINATION OF ROMAN INFRASTRUCTURE AND INTERVENTIONS IN RESPONSE TO HYDROLOGICAL RISK IN THE PO–VENETIAN PLAIN

Water poses a particular challenge to the cities and settlements of the Po–Venetian plain. The region has some of the highest levels of precipitation in Italy and is criss-crossed by dozens of rivers, including the Po, Adige and Tagliamento. Throughout history, there was considerable hydrological risk to the well-being of riparian communities from hazards such as flooding and lateral channel movement, yet local residents did not sit idly by. This article synthesizes the available evidence for Roman responses to hydrological risk in the Po–Venetian plain from the first century BC to the sixth century AD, examining their workings and the hazards they sought to counteract, integrating them into wider discussions on risk in the Roman world. The responses are divided into the categories of defensive works (embankments and dykes) and channel interventions (channel rectification, channel diversion and dredging). While the effectiveness of these methods is questioned, in particular their potential to cause unintended changes to the watercourse, the decision by riparian communities to undertake them suggests a degree of local success. Nevertheless, an examination of the archaeological and palaeoclimatic evidence suggests a discrepancy between peak intervention and peak risk, implying increasing vulnerability and risk acceptance amongst riparian communities during late antiquity. L'acqua pone una particolare sfida alle città e agli insediamenti della pianura padano-veneta. La regione è caratterizzata da alcuni tra i più alti livelli di precipitazioni in Italia ed è attraversata da molti fiumi, tra cui il Po, l'Adige e il Tagliamento. Nel corso della storia, le comunità rivierasche hanno dovuto affrontare un notevole rischio idrologico legato a inondazioni e instabilità dei canali laterali. Gli abitanti dell'area non sono certamente rimasti a guardare. Questo articolo propone una sintesi delle evidenze disponibili relativamente alle risposte romane al rischio idrologico nella pianura padano-veneta dal I secolo a.C. al VI secolo d.C., esaminando il loro funzionamento e i pericoli che hanno cercato di contrastare, integrandole in più ampie discussioni sul rischio nel mondo romano. Le soluzioni individuate per arginare il rischio idrogeologico sono suddivise nelle categorie di opere difensive (argini e fossati) e interventi di canalizzazione (modifiche e deviazioni dei canali e dragaggio). Sebbene l'efficacia di questi metodi sia stata messa in dubbio, in particolare la loro possibilità di causare cambiamenti non intenzionali al corso d'acqua, la decisione delle comunità rivierasche di adottarli suggerisce un certo grado di successo locale. Tuttavia, un esame delle testimonianze archeologiche e paleoclimatiche suggerisce una discrepanza tra il picco di intervento e il picco di rischio, implicando una crescente vulnerabilità e un'accettazione del rischio tra le comunità rivierasche durante la tarda antichità.

Temperature Dependent Analytical Model for the Threshold Voltage of the SiC VJFET with a Lateral Asymmetric Channel

The wide-bandgap (WBG) semiconductor devices for modern power electronics require intensive efforts for the analysis of the critical aspects of their operation. In recent years, silicon carbide (SiC) based field effect transistor have been extensively investigated. Motivated by the significant employment of the SiC Vertical Junction Field Effect transistors with lateral channel (LC-VJFET) in the development of high-voltage and high temperature applications, the properties of the LC-VJFET device are investigated in this work. The most important normally-ON LC-VJFET parameter is their threshold voltage (VTh), which is defined as the gate-to-source voltage necessary to block the device. The higher complexity of the blocking operation of the normally-ON device makes the accurate knowledge of the VTh as a fundamental issue. In this paper, a temperature dependent analytical model for the threshold voltage of the normally-ON LC-VJFET is developed. This analytical model is derived based on a numerical analysis of the electrical potential distribution along the asymmetrical lateral channel in the blocking operation. To validate our model, the analytical results are compared to 2D numerical simulations and experimental results for a wide temperature range.

Influence of Emitter Structure on Its Hydraulic Performance Based on the Vortex

The rectangular labyrinth emitter is taken as the study object in this article, as we added internal teeth to vortex-free and vortex areas in its lateral channel or lengthened the vertical channel, to change the channel structure. Using the computational fluid dynamics (CFD) method simulates the water flow field, to get the relationship between flow rate and pressure, and the vortexes distribution in channel. The aim of this study is to explore the reasons for the influence of structural change on hydraulic performance of the emitter through the analysis of vortex intensity and its distribution from the perspective of the vortex. The results show that the relative error of simulated results and experimental data was 1.02–2.11%. Adding internal teeth to vortex-free areas in lateral channel can improve hydraulic performance of the emitter; adding them to vortex areas can reduce it. The increase in vortex number and intensity in flow field is the internal reason for the improvement of the emitter’s hydraulic performance. The channel structure changes promote the formation of a larger velocity gradient, and the increase in the velocity gradient in flow field exacerbates vortex formation. Changing channel structure to improve the emitter’s hydraulic performance can promote an increase in the number and intensity of vortexes in the channel.

Laterally accreting sinuous channels and their deposits: The Goldilocks of deep-water slope systems

ABSTRACT Channels with a sinuous planform are common in both continental and deep-marine environments on Earth, and similarly in high-resolution images of the surface of Mars. Whereas common in rivers, continuous lateral channel migration and point-bar deposition appear to be much less common in the deep sea. In the bends of rivers, near-bed flow driving point bar growth results from a cross-flow superelevation of the water surface that sets up a lateral hydrostatic pressure gradient driving an inward-directed flow near the bed. However, in deep-marine systems the surface between the turbidity current and overlying ambient fluid sits well above the channel margins, and therefore precludes a similar lateral superelevation of the current top. Here it is argued that the cross-flow component is related to a density gradient that mimics the effect of the hydrostatic pressure gradient in rivers, and develops as coarse suspended particles that experience little uplift, and therefore negligible overspill, become concentrated along the outer bank. This condition develops best in a two-part suspension made up of a highly concentrated, unstratified basal plug of coarse sediment overlain sharply by a dilute cloud of much finer sediment—a density structure that differs from the more typical upward exponential decrease in density. The abundance of coarse and fine sand, but depletion in the intermediate grain size fraction, is related to transgressive shelf processes and its influence on sediment supplied to the system, and in turn, the flow structure of the current. It is under these seemingly uncommon granulometric conditions that continuous laterally migrating channels, and accordingly, riverine-like point-bar deposition, is most common in the deep sea.

A remote sensing-based evaluation of channel morphological characteristics of part of lower river Niger, Nigeria

River bank erosion, accretion and lateral channel migration are important geomorphological processes, which attract a great deal of attention of river engineering scientists in many parts of the world. The present study assesses the morphological characteristics of parts of the lower section of River Niger, where field data are scarce and difficult to access for security and cost implications. Multi-date (1990, 2002 and 2017) Landsat imageries were used for the study, the imageries were corrected for geometric and radiometric errors, classified and analysed for changes in major land cover classes within the river channel, to assess river planform, riverbank pattern, channel width, bankline migration and centreline using ArcGIS software. The results revealed a decrease in water body and riparian vegetation by 27.64% and 9.77%, respectively, between 1990 and 2017. Sediment yield, however, increased by 75.61%. In addition, the river channel exhibited significant spatial changes within the study period; centreline at left flange shifted eastwards by about 1347.3 m at the upper section but westward at the lower section by 123.1 m. The bankline shifted prominently eastwards at right flange and westwards at the right flange. The study concluded that the studied channel had actually undergone some critical morphological changes greatly affected by erosion and accretion processes that are easily captured with remote sensed imageries.