River Thalweg Research Articles

Freeze-Up Ice Jam Formation in the River Bend, a Case Study on the Inner Mongolia Reach of Yellow River

Concern has been expressed regarding the impacts of climate change on river ice and ice jam formation in cold regions. Ice jams are easily initiated in bends and narrow channels and cause disasters. In this study, observations and remote sensing monitoring are used to study the freeze-up ice jam formation of bends. Sediment transport and freezing process of the river interact, influencing bed changes profile and sedimentary budget. River ice processes, channel evolution, ice hydro-thermodynamics, and ice jam accumulation are explored. The results show that the channel topography determines the river thalweg, and that the channel elevation interacts with the river ice through sediment transport. The channel shrinkage increases the probability of ice jam, and the sharp bend is prone to ice jam formation. Under the effect of secondary circulation flow in the bend and in the outer bank, the juxtaposed freeze-up and the hummocky ice cover occur in the same location, and frazil ice accumulates under the junction of the main channel and the shoals. Affected by the increase of the hydraulic slope and the velocity downstream, open water reaches develops downstream of the ice accumulation. An open water section is emerged upstream of the bend, due to the ice deposition, and partly cut-off supply of the frazil.

Utilizing The HEC-RAS Sediment Model in Prediction of the Optimal Navigation Path for The Nile River Reach Downstream Esna Barrages

A one-dimensional numerical model (HEC-RAS) was calibrated to simulate morphological changes in the study reach of the Nile River downstream of Esna barrages by using the available field data of the years 2010 and 2013. The presented research utilizes the synergies between GIS and HEC-RAS in studying the morphological changes in the study area that affects directly the navigation condition and Proposes the optimum navigation path in the selected study reach based on the numerical model results data. Using data measurements, the model was calibrated and verified. It gave a reasonable agreement between the calculated and measured values for the water level and the morphological changes in the selected cross-sections and along the River's thalweg with accuracy 99.63% and 96.66% for hydraulic and sediment calibration and verification. It can be concluded from several runs of the model that the best equation for predicting morphological changes within the study area is the Ackers-White equation. Finally, the results indicate that the HEC-RAS model presents a satisfying performance for sediment transport.

THE EFFECT OF WEST QURNA OILFIELD ON THE PART OF EUPHRATES RIVER, NORTHERN BASRA GOVERNORATE, IRAQ: GEOMORPHIC AND STRUCTURAL GEOLOGY INTEGRATED ANALYSIS

AbstractThe study utilized geomorphic and structural geology analysis integrated analysis to understand the effect of West Qurna Oil Field (or West Qurna Structure) on the part of Euphrates river route, whether it’s related to neotectonic activity or it’s a natural phenomenon. The Euphrates River Drainage Basin is located in the northern part of the Basra governorate in the south of the Mesopotamian Basin. The channel of the river is mostly straight and characterized by large loops. The channel sinuosity of this river system is analyzed in order to draw conclusions on the neotectonic activity of the region. The original status of the river thalweg was digitized from recent satellite images using the new Landsat 8 Scenes. Sinuosities at different sample section lengths were computed in a GIS software environment ArcGIS 10, providing so-called ‘sinuosity spectra’ for each point of the analyzed using a moving-window method and different window sizes channels. High sinuosity sections were correlated to geological subsurface structures of West Qurna Oil Field identified, indicating their neotectonic activity. A structural analysis (geometric and genetic analyses) performed to identify its type, origin and to find its relevance to main regional tectonic events. The geometric analysis detect that the bending fold mechanism (vertical force) could responsible about form West Qurna oil. Thus, thinning feature associated with West Qurna Oil Field. This mechanism could be connected with growth of salt structure of Hormuz Salt below it as confirmed by negative residual anomaly associated with West Qurna Oil Field.

Two pool-to-pool spacing periods on large sand-bed rivers: Mega-pools on the Madeira and Mississippi

The Madeira River thalweg includes two pool-to-pool spacing periods. First, standard pool-crossing sequences form 6 to 8 m deep pools. These pool-crossing sequences recur approximately every six channel widths (9.7 km or 6.8 W), on average. However, the Madeira study reach (between Manicoré and Porto Velho in Northern Brazil) is relatively straight, making these pools more frequent than meanders. Second, much deeper pools (13 to 30 m deep) also form at relatively regular, but much longer spacing (50–60 km, about 40 channel widths apart). The deeper “mega-pools” occur where the river reaches the edge of the Holocene alluvium, encountering resistant units (e.g., granite, mud clasts, and conglomerates) in the confining Pleistocene units. These two pool scales also occur on the Lower Mississippi River (downstream of Tarbert Landing). This study identified pool formation processes responsible for these two pool-depth and –spacing scales on two large sand-bed rivers. The analyses computed pool statistics and correlated the deepest pools with planform controls. Two distinct pool formation hypotheses explain the two pool types. The standard pools are “rhythmic” features, developed by macro-turbulent feedbacks, while the mega-pools are “forced” features imposed by the regional geology. The former are fundamentally periodic; the latter are not. However, periodogram analysis indicates that mega-pools on the Madeira form a second, relatively regular pool period. The regional geology, including the confining Pleistocene bluffs and, potentially, orthogonal neotectonic lineaments, imposed periodic regularity to these mega-pools on the Madeira River that is not observed on the Mississippi River, a comparably-sized sand-bed river with mega-pools.

Floodplain Terrain Analysis for Coarse Resolution 2D Flood Modeling

Hydraulic modeling is a fundamental tool for managing and mitigating flood risk. Developing low resolution hydraulic models, providing consistent inundation simulations with shorter running time, as compared to high-resolution modeling, has a variety of potential applications. Rapid coarse resolution flood models can support emergency management operations as well as the coupling of hydrodynamic modeling with climate, landscape and environmental models running at the continental scale. This work sought to investigate the uncertainties of input parameters and bidimensional (2D) flood wave routing simulation results when simplifying the terrain mesh size. A procedure for fluvial channel bathymetry interpolation and floodplain terrain data resampling was investigated for developing upscaled 2D inundation models. The proposed terrain processing methodology was tested on the Tiber River basin evaluating coarse (150 m) to very coarse (up to 700 m) flood hazard modeling results. The use of synthetic rectangular cross sections, replacing surveyed fluvial channel sections, was also tested with the goal of evaluating the potential use of geomorphic laws providing channel depth, top width and flow area when surveyed data are not available. Findings from this research demonstrate that fluvial bathymetry simplification and DTM resampling is feasible when the terrain data resampling and fluvial cross section interpolation are constrained to provide consistent representation of floodplain morphology, river thalweg profile and channel flow area. Results show the performances of low-resolution inundation simulations running in seconds while maintaining a consistent representation of inundation extents and depths.

La influencia del relieve en la isla de calor de Madrid: las vaguadas del Manzanares y del Abroñigal

La influencia del relieve en la isla de calor de Madrid. Las vaguadas del Manzanares y del Abroñigal. Resumen. Se estudia la influencia de la topografía y de diversos usos de suelo en la isla de calor urbana de Madrid, a través de dos perñles en las vaguadas del río Manzanares desde el extrarradio, donde se favorece la entrada de aire frío del exterior de la ciudad, y del Abroñigal en una disposición más urbana.
 
 [fr] Influence du ralief dans l'île de chaleur à Madrid. Les thalwegs du Manzanares et de lAbroñigal. L'étude de l'influence de du relief et des différents paysages urbaines sur l'île de chaleur de la ville de Madrid a été affectuée à partir de deux coupes, l'une dua thalweg du Manzanares dans les faubourgs, où l'on trouve l'air froid de l'extérieur de la ville, et l'autre du thalwg de 1'Abroñigal, situé bienplus à l'intérieur de la cité.

Hybrid kriging methods for interpolating sparse river bathymetry point data

ABSTRACT Terrain models that represent riverbed topography are used for analyzing geomorphologic changes, calculating water storage capacity, and making hydrologic simulations. These models are generated by interpolating bathymetry points. River bathymetry is usually surveyed through cross-sections, which may lead to a sparse sampling pattern. Hybrid kriging methods, such as regression kriging (RK) and co-kriging (CK) employ the correlation with auxiliary predictors, as well as inter-variable correlation, to improve the predictions of the target variable. In this study, we use the orthogonal distance of a (x, y) point to the river centerline as a covariate for RK and CK. Given that riverbed elevation variability is abrupt transversely to the flow direction, it is expected that the greater the Euclidean distance of a point to the thalweg, the greater the bed elevation will be. The aim of this study was to evaluate if the use of the proposed covariate improves the spatial prediction of riverbed topography. In order to asses such premise, we perform an external validation. Transversal cross-sections are used to make the spatial predictions, and the point data surveyed between sections are used for testing. We compare the results from CK and RK to the ones obtained from ordinary kriging (OK). The validation indicates that RK yields the lowest RMSE among the interpolators. RK predictions represent the thalweg between cross-sections, whereas the other methods under-predict the river thalweg depth. Therefore, we conclude that RK provides a simple approach for enhancing the quality of the spatial prediction from sparse bathymetry data.

Examining Spatio-Temporal Change Detection in the Indus River Delta with the Help of Satellite Data

The morphology of a river thalweg in a deltaic environment is continuously reshaped by the interactive balancing of the fluvial and marine hydrodynamic processes. Fluvial flow parameters such as volume and flow velocity are favorable to increase the width of thalweg and develop a braided pattern in river course within a delta region. The present study utilized historical satellite images to show that as result of the development of the world largest water divergent networks, the Indus River discharge and sediments load discharge into the Indus delta have been enormously depleted in the last 150 years. Satellite images revealed significant and successive narrowing of the thalweg and distinct widening of the course of the Indus River near the delta. Based on the model results, we show that the style of the rapid morphological changes demonstrates seaward widening and the landward narrowing of the Indus river course and its thalweg. Our results indicate that anthropogenic diversions of the flow in the upstream region of the Indus River have resulted in the devastating domination of marine hydrodynamic processes over the weakened and destabilized natural fluvial processes in the delta region.

The Ebro River in the 20th century or the ecomorphological transformation of a large and dynamic Mediterranean channel

ABSTRACTIn the first decades of the 20th century, the Ebro River was the Iberian channel with the most active fluvial dynamics and the most remarkable spatial‐temporal evolution. Its meandering typology, the dimensions of its floodplain, and the singularities of its flow regime produced an especially interesting set of river functions.The largest dynamics of the Ebro River are concentrated along the meandering profile of the central sector. During the 20th century, this sector experienced a large alteration of its geomorphological structure. We present here an analysis of this evolution through the cartographic study of a long segment of the river (~250 km) in 1927, 1956 and 2003. The results show a large reduction in bank sinuosity, a progressive loss of fluvial territory, and a large decrease in channel width. These changes are especially clear in the areas previously most ecologically connected with the active channel. The fluvial territory of the river in 2003 was approximately half that found during the first decades of the 20th century. Forest plantations, which were non‐existent in 1927, occupied more than 1500 ha of the study area in the last decade.This intense geomorphological transformation becomes ecologically visible in (i) a 35% reduction of the area occupied by riparian vegetation; (ii) a loss of the heterogeneity of riparian forest spots, which were formerly structured in an irregular mosaic far from the river thalweg; and (iii) a modification of the riparian forest structure, which is currently linear, uniform, thin and very close to the river axis. The ecomorphological alteration was intensified by the remarkable reduction in bank length (13%) and the reduced dynamism of the present river system, indicated by an increase in the percentage of fluvial territory occupied by riparian forests and a reduction in the area occupied by the active channel. Copyright © 2002 John Wiley & Sons, Ltd.

Contexto geomorfológico y principales rasgos tecnológicos de nuevos yacimientos del Pleistoceno Medio y Superior en el Valle Inferior del Manzanares (Madrid, España)

The archaeological works developed during the years 1996 in the site of Tafesa, 2005 in the 12 de Octubre Metro Station site and 2006 in the confluence of the Butarque Stream (Villaverde-Barrio de Butarque site) located south of the Madrid City (Spain), have provided new lithic assemblages. These assemblages have been stratigraphically contextualized in the Pleistocene deposits of the Lower Manzanares river valley within the so-called “Manzanares Complex Terrace” (TCMZ). This fluvial terrace constitutes an anomalous thickened (20-15m) deposit at +22-16m above the present river thalweg mainly developed along the right (southern) valley margin. This fluvial level has been traditionally considered of middle Pleistocene age on the basis of the acheulian lithics and faunal assemblages typically located within its lower stratigraphic layers. Certainly, the Tafesa is a fluvial terrace site at +22 m with acheulian industry and middle Pleistocene faunal remains at its lower sedimentary sequence. However, the upper sedimentary levels of this same terrace in the 12 de Octubre y Villaverde-Butarque sites throw lithic assemblages of the lower and upper Paleolithic belonging to upper Pleistocene, as suggested by the available set of TL and OSL dates for the zone. The analyses developed in this study indicate that the development of this thickened fluvial terrace started during the end of the middle Pleistocene, but also comprise the whole Oxygen Isotopic Stage OIS 5 during the upper Pleistocene.

Neotectonic evolution of the northern Laborec drainage basin (northeastern part of Slovakia)

This study investigates the influence of neotectonic activity on river and basin patterns in a mountainous area located in the northeastern part of the Carpathian Belt (the Laborecká vrchovina and Bukovské vrchy Mts. in eastern Slovakia). This area evolved within the accretionary wedge of the Carpathians during the Neogene, and it was alsowas affected by Middle to Late Miocene thrusting of the External Carpathians. Morphometric analysis, longitudinal and transverse river valley profiles, analysis of basin and valley symmetries, and investigation of alluvial terraces were carried out on the northern Laborec River and its tributaries. This was done to detect a possible relationship between their river courses and any ongoing neotectonic activity, which is otherwise difficult to detect by methods of structural geology because of the poorly exposed area. The general topography of the basin is characterized by a stepwise inclination to the SW as a result of differential uplift and subsidence. The reorganization of the river network in the Laborec drainage basin was influenced by tectonic activity along the NE–SW up to N–S fault structures during the neotectonic phase (Pliocene–Quaternary). The movement along these fault structures is predominantly normal to transtensive. The obtained data assumes that the region is under approximately NE–SW oriented S H compression and NW–SE trending S h tension. The Laborec drainage basin is characterized by a very high degree of asymmetry that sharply increases from the upper to the lower courses of the river. The right-bank tributaries of the Laborec River are < 12 km in length; however, the left-bank tributaries such as Vydraňka, Ol'šava, Výrava, Udava, and Cirocha Streams are up to 50 km long with a high potential of headward erosion and capturing. The valley asymmetry is also very variable in the upper and lower portions of the basin. Based on these presented results, the ancient river thalweg was located along the axis of the Hostovice–Habura depression, and it was captured by the Ol'šava, Výrava, and Udava Streams. The asymmetric pattern of the drainage basin is the result of active tectonics, the continual subsidence of the Transcarpathian Basin, and by the uplift of the Laborecká vrchovina and Bukovské vrchy Mts. These events caused rejuvenation of the headward erosion of streams in the southern part. Favorable lithology was also essential in the process of river capture.

Shifting Modes of the Paraná River Thalweg in its"Braided"Middle-lower Reaches

Shifting Modes of the Paraná River Thalweg in its"Braided"Middle-lower Reaches

Interplay between river discharge and topography of the basin floor in a hyperpycnal lacustrine delta

AbstractBasin‐floor topography influences the flow path of hyperpycnal plumes and delta morphology during progradation of the Red River delta in Lake Texoma, USA. The Red River discharge is typically a hyperpycnal plume due to elevated total dissolved solids. Because the river plume is a bottom‐hugging hyperpycnal flow, lake bathymetry and topography strongly influence deposition and subsequent delta morphology. In addition to elevated total dissolved solid concentrations compared with Lake Texoma water, the density contrast of the Red River outflow is increased by high suspended‐sediment concentrations during high‐discharge events. Steep lateral slopes in the Lake Texoma basin deflect hyperpycnal river plumes and, subsequently, change the delta progradation direction before the delta reaches the opposite bank of the lake. Analysis of multi‐temporal aerial and satellite images indicates that the hyperpycnal delta follows the steepest lake‐bottom gradients, corresponding to the pre‐impoundment river thalweg (i.e. bypassing shallow parts of the lake). An analytical model for the hyperpycnal‐plume trajectory indicates plume deflection during low‐discharge or high‐discharge events, towards the deepest part of the basin. The magnitude of plume deflection is a function of river discharge and basin‐margin gradients. Plume deflection can vary between 10° and 80° from the channel axis towards the old river thalweg. The high deflection appears in the case of maximum basin side gradients of 12·8° and in conditions of low river discharge. During low‐discharge periods, the Red River delta builds a lobate shape with multiple terminal distributary channels whereas, during high‐discharge periods the Red River delta builds an elongate shape with a single large distributary channel. The elongate morphology of the delta is formed through the development of a single distributary channel and abandonment of the other distributaries. Therefore, the lobate shaped delta is expected to be preserved in the rock record.

Species-Specific Spatial and Temporal Distribution Patterns of Emigrating Juvenile Salmonids in the Pacific Northwest

The vertical and horizontal distribution of juvenile salmonid migrants on approach to the dams influences bypass success in rivers. Accordingly, fish distributions have been studied for nearly three decades. These studies, however, have not been integrated and summarized in a single body of work to determine overall patterns in the spatial distribution of emigrants. We reviewed peer-reviewed and gray literature to summarize species-specific trends in the horizontal and vertical distributions of emigrating salmonids as measured by several different methods. We found that there were no species-specific differences in horizontal distributions and that fish were often oriented with the river thalweg. There were weak differences between species in vertical distributions, e.g., juvenile yearling steelhead were shallower during the day than yearling Chinook salmon. For sockeye, coho, and subyearling Chinook salmon, the data were limited or conflicting. Studies were purposefully designed to measure distributions at certain dams under particular environmental conditions for specific, local purposes. The non-standard sampling design has hampered the development of testable hypothesis on fish distributions in the Snake and Columbia rivers. Recent advances in individual-based models are offering the potential to forecast fish distributions near dams and facilitate improved bypass system design.

Alluvial gully erosion: an example from the Mitchell fluvial megafan, Queensland, Australia

AbstractConsiderable attention has been focused on the role of gullies as a contributor to contemporary sediment loads of rivers in Australia. In southern Australia rapid acceleration of hillslope gully erosion has been widely documented in the post‐European period (∼ last 200 years). In the northern Australian tropics, however, gully erosion processes operating along alluvial plains have not been well documented and can differ substantially from those gullies eroding into colluvium on hillslopes. Aerial reconnaissance surveys in 2004 along 13 500 km of the main stem rivers that drain into the Gulf of Carpentaria (GoC), identified extensive areas of alluvial lands that have been impacted by a pervasive form of gully erosion. More detailed remote sensing based mapping within the 31 000 km2 Mitchell River fluvial megafan has identified that active gullying into alluvium occupies ∼ 0·4% (129 km2) of the lower Mitchell catchment. These alluvial gullies are concentrated along main drainage channels and their scarp heights are highly correlated to the local relief between the floodplain and river thalweg. While river incision into the megafan since the Pleistocene has developed the relief potential for erosion, other factors such as floodplain hydrology, soil dispersibility, and vegetation also influence the distribution of gullies. In this paper we present a conceptual model of alluvial gullies, and contend that they represent a distinct end member in the continuum of gully forms that have been described in the geomorphic literature. An understanding of the processes driving this form of alluvial gullying can only be gained when they are differentiated from widely described colluvial hillslope gully models and theories. We present evidence of type examples of alluvial gullying in the Mitchell, and through analysis of their distribution and morphology at different scales, highlight some of the key mechanisms that are potentially initiating these features and driving their expansion. Copyright © 2009 John Wiley &amp; Sons, Ltd.

A review of the Tagus river tufa deposits (central Spain): age and palaeoenvironmental record

Here we determined the aminostratigraphy and aminochronology of tufa deposits located in central Spain associated with the Tagus river and some of its tributaries (the Henares, Dulce, Cifuentes, Ruguilla, Trabaque, Escabas and Guadiela rivers). We used aspartic acid and glutamic acid racemization ratios obtained from the ostracod Herpetocypris reptans. Tufa accumulations were found to be of different origins; those in the Henares, Cifuentes and Ruguilla rivers are of paludal origin, while those in the Dulce and Tagus rivers are of fluvial origin. A generally good correspondence was found between the age of the deposits and the position of the terraces above the current thalweg. However, the geomorphological evolution of the Henares, Cifuentes and Ruguilla rivers (infilling of pre-existing valleys) has produced deposits of distinct ages at the same elevation above the current river thalweg, and sometimes, older tufas are located below younger ones. We distinguished eight main tufa-deposition episodes. These occurred predominantly during even Marine Isotopic Stages (MIS), at 406 ± 90 (MIS 11), 264 ± 68 (MIS 7e), 189 ± 40 (MIS 7a), 130 ± 27 (MIS 6-5e), 101 ± 25 (MIS 5c), 32 ± 10 (MIS 3), 14 ± 4 (MIS 1), and 6 ± 2 (MIS 1) ka. These results are in agreement with the dating of similar deposits from nearby areas and other zones of Spain and Europe. The tufa stable-isotope compositions were similar to other examples in central and southern Spain and their plot falls in the same field as other lowland European stream tufas. Oxygen stable isotopes were influenced mainly by temperature and rainfall. The δ 13C values indicated a major effect of soil-derived carbon rather than carbon from the catchment area, but moderated in each tributary by evaporation, flow regime and biological effects (photosynthesis).