Meandering Research Articles

Sensitivity of a meandering lowland river to intensive landscape management: Lateral migration rates before and after watershed-scale agricultural development

Agricultural development has transformed the vegetation cover of many landscapes around the world, thereby altering water and sediment fluxes to river systems. Past work in the upper midwestern United States, particularly in areas of moderate relief, has shown that increases in water and sediment fluxes associated with agricultural development have dramatically altered river dynamics. Less is known about how agriculture has affected river dynamics, particularly rates of lateral migration, in relatively low relief landscapes of the Midwest shaped by glaciation during the Wisconsin Episode. This research examines rates of lateral migration of a channel bend along a lowland meandering river in Illinois, USA before and after agricultural development. The rate of lateral migration prior to agricultural development is estimated through dating of carbonaceous material within lateral-accretion deposits underlying distinct meander scrolls. The rate of lateral migration after agricultural development is determined from analysis of changes in river-channel position determined from survey records, aerial imagery, and digital elevation data. Average rates of migration before and after agricultural development are similar, suggesting that agricultural development has not substantially affected rates of lateral migration of the river. Some accelerated movement occurred locally following agricultural development, but this movement cannot be definitively tied to landscape transformation. Possible factors responsible for the lack of sensitivity of the river system to agricultural development include high resistance of the cohesive, tree-lined riverbanks to erosion and the low bankfull stream power per unit area of the modern river. From a management perspective, the study highlights the importance of bank vegetation in maintaining channel stability in low-relief agricultural landscapes.

Effect of the transition section on the flow structure of consecutive river bends with point bars

The transition section (TS), linking the front bend and the back bend in consecutive river bends, plays a key role in the flow hydraulic characteristics, sediment transport, and riverbed evolution in meandering rivers, which is crucial for flood control, navigation, and river stability. Most existing studies on the hydraulic effect of the TS focus on flat-bed scenarios, rendering an inadequate understanding of the TS in consecutive bends with point bars, often found in natural rivers. Based on three-dimensional numerical simulations, the effects of the length and the topography of the TS are investigated in detail on the flow structure in consecutive bends with point bars, respectively. The results reveal that without an adequate TS length, the residual circulation of the front bend (RC) inhibits the development of the main circulation in the back bend (MC), causing the positions of the maximum strength of the MC and the maximum value of cross-section-averaged turbulent kinetic energy (<tke˜>) in the back bend moving upstream. As the length of the TS increases, the above effect of the front bend gradually decreases. The critical length of the TS to fully decay the RC is 4.8 times the bend width (B) in consecutive bends with point bars, longer than that (4B) in the flat-bed bend. Furthermore, the central bar in the TS is found to facilitate the generation of the outer bank cell and accelerate the decay of the RC. These effects of the TS can profoundly change the flow hydraulics, sedimentation, and stream stability of consecutive bends. The results of the study will help to further understand the linkage role of the TS in consecutive bends and may serve as a rational reference for managing natural meandering rivers with multiple hydrological, geomorphological, and/or ecological goals.

Potential Dam Breach Flood Assessment with the 2D Diffusion and Full Dynamic Wave Equations Using a Hydrologic Engineering Center-River Analysis System

Dam breaches have catastrophic consequences, causing severe property damage, life loss, and environmental impact. The potential dam breach downstream flooding of the Kulekhani reservoir, Nepal, was studied using a 2D Diffusion Wave Equation (DWE) and Full Dynamic Wave Equation (FDWE) through an open-source solver, Hydrologic Engineering Center-River Analysis System (HEC-RAS). The suitable dam breach model was identified based on the dam geometry and sixteen historical dam failure cases. The simulated downstream peak was tested with an empirical relation, considering reservoir volume and duration of failure. Model comparisons through the flood plain mapping of water depth, flow velocity, flood intensity as per guidelines of the American Society of Civil Engineers (ASCE), and arrival time were carried out for flood hazard assessment. FDWE was able to capture the physical flow phenomena in the river bend resulting in higher flow velocity at the outer bend, lower velocity at the inner bend, and formation of eddies due to the application of the turbulence model, considering possible momentum losses, whereas DWE was unable to capture these effects due to a simplified momentum equation. The total area of flood extension was found to be increased by 30% using FDWE than the DWE due to higher water surface elevation. Most of the towns along the Kulekhani River were classified as “Very High” intensity flood regions according to ASCE, due to the V-shape valley. The peak time difference at the Bagmati River confluence was evaluated between the models. This plays an important role in decision-making for the selection of the flood model to make a safe evacuation plan. The application of FDWE was found to be suitable for the rapidly varying unsteady flow in the steep meandering river.

Facies Variability in Paleogeographic Trends from Core Data in the Lower and Middle Frio Formation in South Texas

This core-based study of the Oligoene lower and middle Frio formation in South Texas documents facies variability, depositional systems, and sandstone-body architecture in the lower and middle Frio formation in South Texas. A previous study by the Bureau of Economic Geology (BEG) in 1982 characterized the Frio Formation in terms of depositional systems, structural framework, hydrocarbon origin, migration, and exploration potential. Paleogeographic trends in the 1982 study were delineated for the lower, middle, and upper Frio Formation, based mostly on wireline-log data. Core data in this study augment and refine facies interpretations and clarify depositional styles in four paleogeographic trends from the 1982 study in the lower and middle Frio Formation. These trends include (1) lower delta plain/margin, (2) aggradational fluvial, (3) aggradational (multistoried) barrier, and (4) floodplain. With minor exceptions, this study validates and refines interpretations of the regional distribution of lower and middle Frio paleogeography in South Texas in the 1982 study. Four (4) main results of this study include (1) documenting lithology and facies types in these paleogeographic trends, (2) demonstrating that these paleogeographic trends are a composite of multiple transgressive-regressive (T–R) cycles, (3) providing evidence that these fluvial systems are mixed-load, meander belt in origin rather than coarse-grained bedload in origin, based on vertical grain-size profiles and the presence of paleosols that indicate stable, well-developed floodplains, and (4) identifying anomalous occurrences of sandstone-rich fluvial-channel systems in areas previously mapped as sandstone-poor and interpreted to be primarily floodplain in origin. Finally, this study serves as an example of the value of core data in refining interpretations of paleogeography and depositional systems in stratigraphic units that are a composite of multiple T–R episodes.

Relationship Between Emotion Regulation Difficulties and Gambling Tendencies of University Students.

This study aims to examine the relationship between university students' difficulties regulating emotions and their tendency to gamble. The population of this cross-sectional and correlational study consisted of 69,000 undergraduate level students studying at three state universities in three different provinces in Turkey between February-September 2022. Based on the calculation using the sampling method of the known population, study data were collected face-to-face from 750 students. The data were collected using three tools: a descriptive information form, the South Oaks Gambling Screening Test (SOGS), and the Difficulties in Emotion Regulation Scale-Brief Form (DERS-16). Descriptive statistics, Pearson correlation and Multiple Linear Regression analysis were used to analyze the relationship among the scales' mean scores. Of the participating university students, 51.6% were female and 48.4% were male. Of these students, 42% stated that they had gambled at least once in their lives and 25.3% of them were still gambling. The mean DERS score was 38.14±14.37, which indicated a moderate difficulty in emotional regulation, and the mean SOGS score was 5.12±3.18. A positive and significant correlation was found between DERS SOGS (r=0.304, p<0.05). It was determined that university students' tendency to gamble was predicted by the three sub-dimensions of the DERS (Clarity (β=0.258, p=0.001), Purpose (β=0.156, p=0.021) and Non-Acceptance (β=1.768, p=0.001)), being male and gambling status in the family (p<0.05). Emotional regulation difficulties in university students may play an important role in their gambling tendencies.

Meanders of the Kabodak River, Bangladesh

The study explores the meandering patterns of the Kabodak River and investigates the relationship among geometric aspects like sinuosity, width, amplitude, radius of curvature, and wavelength. The variables like basin area, river length, and longitudinal profile were measured, and the geometric aspects such as sinuosity, radius of curvature, meander wavelength, and meander amplitude were interpreted and calculated using Google Earth Pro and ArcGIS 10.5. With the aid of the software SPSS and unscrambler X, the relationship among the geometrical aspects was examined. Besides, different meander patterns have been identified by analyzing the meander form. The result reveals that the upper and lower parts of Kabodak appear more sinuous than the middle. Nodal patterns in river sections vary, with the upper and lower sections experiencing increased sinuosity due to lower gradients, reduced flow, and blockage. In contrast, the middle section exhibits less sinuous characteristics because of neotectonics upliftment. Among the variables, meander wavelength, amplitude, and radius of curvature have weak positive correlations between and among them, except for the wavelength-amplitude relation. The relationship between wavelength and amplitude is inversely proportional. The variable width appears non-responsive with other variables, which makes sense as the river's width is already structuralized due to human interference. Theoretically, the Kabodak River's meandering pattern deviated from other meandering river studies due to human interference. Similar types of work on other meander rivers of the delta may be explored to see if the result corroborates. Besides, the effect of human intervention on meandering patterns and morphological processes needs further study. J. Asiat. Soc. Bangladesh, Sci. 49(2): 149-164, December 2023

Lithofacies and paleoenvironmental analysis of the Upper Cretaceous successions: Yagaan Khovil fossil locality, central Gobi region, Mongolia

The Upper Cretaceous successions are exposed at the Yagaan Khovil fossil locality in the central Gobi region, Mongolia. The successions comprise fluvial deposits that are divided into two units based on the lithological characteristics of the floodplain deposits. The lower unit (Unit 1) is characterized by eolian-influenced environments, whereas the upper unit (Unit 2) is composed predominantly of meandering river systems with lateral accretionary channel fill deposits that show concretion at the top of the bed. The shift in depositional processes from the lower to the upper unit can be hypothesized as the result of the change in the proximity of the eolian-affected area to the study area. The successions preserving the similar paleoenvironmental transition are also present in the Nemegt Basin, where the successions shift from reddish mud beds affected by eolian processes to meandering fluvial successions. Additionally, to the similar sedimentological features, similarities in vertebrate fossils between Yagaan Khovil and the formations in the Nemegt Basin imply the close relationship between the two areas in terms of environmental conditions, ages, and stratigraphic positions. To enhance the stratigraphic framework of the Upper Cretaceous strata in Mongolia, future work should integrate the findings of this study with new radiometric dating techniques.

Exploring meandering river cutoffs

Abstract Cutoffs, which include neck and chute cutoffs, are the results of the fluvial processes that fundamentally influence evolution of meandering rivers. A neck cutoff happens when the two limbs of a highly sinuous bend touch, whereas a chute cutoff refers to the formation of a shortcut channel passing through a meander bend. In this review, we begin by distinguishing the morphological and hydrological conditions of the two cutoff types. Mechanisms driving the development of a neck cutoff are embodied in a variety of kinematical and hydrodynamic models simulating processes governing the long-term evolution of meandering rivers. These models adopt a morphological threshold for judging the occurrence of a neck cutoff, b = αw , where α is a constant ranging between 0 and 1, b is the bend neck width and w is the mean channel width. The potential underestimation of the evolutionary period during the late stage of bend evolution toward a neck cutoff when using this morphological threshold and the uncertainties in quantifying the migration–curvature relationship limit the abilities of existing models to predict the occurrence of neck cutoffs. We then suggest three possible directions for future research on meander neck cutoffs. Mechanisms controlling chute cutoffs are relevant to six key factors representing the meander hydrological regime, planform morphology, bed topography and floodplain characteristics. The combination of these factors gives rise to four distinguishable triggering mechanisms: headward-erosion, embayment, mid-channel bar and scroll–slough chute cutoffs, though the initiation of the chute cutoff may be caused by some combination of these. However, the hydraulic and morphological characteristics of meander bends under these triggering mechanisms are so complex that they are often site-specific, making it extremely challenging to generalize the known morphodynamic and hydrodynamic processes driving the formation of chute cutoffs in individual meander bends. We close the review by recommending three possible research directions on chute cutoffs for tackling the existing challenges in the future.

Depositional evolution in response to long-term marine transgression in the northern South China Sea

Research on the interaction between depositional evolution process and marine transgression is critical to understanding the transform mechanism of sedimentary systems and guiding hydrocarbon exploration. The early Miocene witnessed the most significant sea-level rise since the Cenomanian, which resulted in extensive marine-influenced deposits worldwide. However, the relationship between the process of depositional evolution and long-term marine transgressions (&amp;gt;1 Ma) remains poorly understood. The Pearl River Mouth Basin in the South China Sea offers a comprehensive deposition record of the early Miocene marine transgression. This study employs high-quality 3D seismic, well-logging, and core data to investigate the impact of the early Miocene transgression on the evolutionary dynamics of the sedimentary system. The regional sea level exhibited a prolonged rise of at least 100 m during the deposition period of the Miocene Zhujiang Formation, corresponding to the long-term marine transgressive in the South China Sea. Throughout this marine transgression, depositional systems developed in the study area include tidal flats, fan deltas, meandering river deltas, and shallow marine shelf sand bodies. The marine transgression process resulted in a significant change in depositional system types, which can be divided into seven units from Unit 1 at the bottom to Unit 7 at the top. The predominant deposition environment transitioned from tidal flats in Units 1-3 to meandering river deltas in Units 4-5, and finally to shallow marine shelf systems in Units 6-7. In the early stage (Units 1-3), the regional uplifts hindered sea level transgression and caused erosion, leading to the development of small-scale proximal fan deltas. In the middle stage (Units 4-5), these regional uplifts submerged, and meandering river deltas dominated with sediments derived from distant extrabasinal sources. During the late stage (Units 6-7), regional sea levels reached their peak, transforming the entire basin into a shallow marine shelf system. Additionally, this marine transgression significantly influenced the distribution of hydrocarbon resources. Notably, the shallow marine shelf sand bodies in Units 6-7 warrant substantial attention for future exploration. This study outlines the complicated transitional processes within depositional systems during long-term marine transgression events, holding relevance for the global evolution of marginal sea basins.

Authoring and Simulating Meandering Rivers

We present a method for interactively authoring and simulating meandering river networks. Starting from a terrain with an initial low-resolution network encoded as a directed graph, we simulate the evolution of the path of the different river channels using a physically-based migration equation augmented with control terms. The curvature-based terms in the equation allow us to reproduce phenomena identified in geomorphology, such as downstream migration of bends. Control terms account for the influence of the landscape topography and user-defined river trajectory constraints. Our model implements abrupt events that shape meandering networks, such as cutoffs forming oxbow lakes and avulsions. We visually show the effectiveness of our method and compare the generated networks quantitatively to river data by analyzing sinuosity and wavelength metrics. Our vector-based model runs at interactive rates, allowing for efficient authoring of large-scale meandering networks.

Morphodynamic of the Kosa River Channel as a Reflection of the Direction of the Channel Processes in the Development Valleys of Glaciolacustrine Terraces (Upper Kama Basin)

Abstract—The article is devoted to identification of peculiarities of development of channel processes in river valleys with distribution of glaciolacustrine terraces. Kosa river was chosen as the largest right tributary of the upper Kama. The resources of GoogleEarthPro and Yandex Maps were used in the process of interpretation of space images and obtaining quantitative information. The morphodynamic types of a river channel was made on the basis of the analysis of elements of floodplain-channel landscape complexes. The indicator of the ratio of the width of the floodplain to the width of the valley was considered as a feature of the development of channel processes in the areas of the distribution of the glaciolacustrine terrace. This ratio is 1 : 1 at the upper Kosa river outside the Kosinskaya Lowland. It is 1 : 9 at the middle Kosa river, and 1 : 3 at the Kosa downstream. The location of the meander belt in the left of the valley side is a feature of the development of channel processes. This indicates the presence of a stable and long-term planform channel changes from the east to the west in the past. The leading morphodynamic channel types are free meanders and confined straight channel for the Kosa upper stream. In the Kosa middle stream, in which most of the valley is represented by a glaciolacustrine terrace, confined bends already play a significant role in the structure of morphodynamic types of a river channel, while maintaining the leading role of free meanders. At the same time, a high proportion of the distribution of the straight confined channel is observed.

On the Vertical Structure of Deep-Ocean Subinertial Variability

Abstract The vertical structure of subinertial variability is examined using full-depth horizontal velocity and vertical isopycnal displacement observations derived from the Ocean Observatory Initiative (OOI). Vertical profiles on time scales between 100 h and 1 yr or longer are characterized through empirical orthogonal function decomposition and qualitatively compared with theoretical modal predictions for the cases of flat, sloping, and rough bathymetry. OOI observations were obtained from mooring clusters at four deep-ocean sites: Argentine Basin, Southern Ocean, Station Papa, and Irminger Sea. Because no single OOI mooring in these arrays provides temperature, salinity, and horizontal velocity information over the full water column, sensor observations from two or more moorings are combined. Depths greater than ∼150–300 m were sampled by McLane moored profilers; in three of the four cases, two profilers were utilized on the moorings. Because of instrument failures on the deployments examined here, only ∼2 yr of full-ocean-depth observations are available from three of the four sites and some 3+ yr from the other. Results from the OOI “global” sites are contrasted with a parallel analysis of 3.5 yr of observations about the axis of the Gulf Stream where much of the subinertial variability is associated with stream meandering past the moorings. Looking across the observations, no universal vertical structure is found that characterizes the subinertial variability at the five sites examined; regional bathymetry, stratification, baroclinicity, nonlinearity, and the forcing (both local and remote) likely all play a role in shaping the vertical structure of the subinertial variability in individual ocean regions.

The Mangking Sandstone Formation of Kuala Tahan to Kampung Bantal: Sedimentology and Depositional Environment

The Mangking Sandstone of Tembeling Group in the Kuala Tahan region records part of the infill of the continental extensional basin formed at the end of the Triassic. Described facies of this formation include sandy matrix conglomerate (that shows evidence of pseudoplastic debris flow and traction-dominated deposition), sandstones with trough, tabular and horizontal stratification, laminated and massive mudstone. Groups of associated facies are arranged into six distinct architectural elements (channel, sandy bedform, crevasse splay, laminated sand sheet, downstream and lateral accretion and floodplain fines), which are constant with a fluvial origin for the succession. The types of architectural elements present and their relationship to each other demonstrate that the Mangking Sandstone preserves a record of a meandering river system.

Using river restoration model to control riverbank erosion in the Old Brahmaputra river of Bengal Basin, Bangladesh

River meandering causes riverbank erosion, which triggers socioeconomic and environmental issues in the riparian region and raises river sedimentation, thus, needing river restoration. This research depicts a channel restoration model to control river bank erosion and susceptible resource management along the Old Brahmaputra River course based on channel characteristics from 1980 to 2021. The secondary data of Landsat satellite time series and SRTM images were collected from the USGS website, while we used Google Earth images to verify the morphological features. Satellite images were on-screen visualized by ArcMap (10.3) to extract the river channels and measure the erosion and accretion areas. Results showed that the Old Brahmaputra River channel shifted its position due to erosion and accretion. Over the last forty-one years, ∼ 52 km2 area was eroded while ∼ 49 km2 area was accreted, and the average shifting of the river channel was 1.3 km2 per year. Accordingly, the river channel has become more sinuous decade by decade and threatens nearby settlements. Hence, this study proposed a river channel based on previous river channels, where the base channel is from the 2000s, which was more stable and flowed through the middle of the floodplain. Parts of the 1980, 2000, and 2021 river channels were also selected, which are relatively far from the susceptible settlements, to draw the proposed restoring channel. This model is likely to aid in developing government strategies for protecting riverbank erosion and river restoration in the forthcoming period. Finally, this study recommends that this newly proposed channel will be conducive to reducing riverbank erosion and the extreme threat to the settlements and their livelihoods.

Paleoenvironments of Late Devonian tetrapods in China

The major evolutionary transition from fish to amphibian included Late Devonian tetrapods that were neither fish nor amphibian. They had thick necks and small limbs with many digits on elongate flexuous bodies more suitable for water than land. Habitats of Devonian tetrapods are of interest in assessing selective pressures on their later evolution for land within three proposed habitats: 1, tidal flats, 2, desert ponds, and 3, woodland streams. Here we assess paleoenvironments of the Late Devonian tetrapod Sinostega from paleosols in Shixiagou Canyon near Zhongning, Ningxia, China. Fossil tetrapods, fish, molluscs, and plants of the Zhongning Formation are associated with different kinds of paleosols, representing early successional vegetation, seasonal wetlands, desert shrublands, and riparian woodlands, and paleoclimates ranging from semiarid moderately seasonal to monsoonal subhumid. The tetrapod Sinostega was found in a paleochannel of a meandering stream below a deep-calcic paleosol supporting well drained progymnosperm woodland in a monsoonal subhumid paleoclimate. This habitat is similar to that of the tetrapods Densignathus, Hynerpeton, and an indeterminate watcheeriid from Pennsylvania, USA. Chinese and Pennsylvanian Late Devonian tetrapods lived in productive woodland streams, choked with woody debris as a refuge from large predators. Habitats of other Devonian tetrapods have yet to be assessed from studies of associated paleosols as evidence for their ancient climate and vegetation.

Why river islands are formed after every big city

The perennial rivers have high and wide catchment areas that supply water continuously to the rivers. So, all through the year, they get water for their activities. Large cities emerge around such rivers and congregate as huge urban clusters like Delhi, Varanasi, and Patna. It was quite interesting to note that in all the big rivers like the Ganges, after crossing all big cities are invariably present, big river islands. The perceived cause of this is the heavy deposits by the people, or the slowing down of the river as it flattens up. The cause of the river islands is only partly the dirt thrown into the river by the people but largely because of the soap detergents and acids that produce large amounts of salts leading to precipitate and coagulation through a process called Cataphoresis of the colloidal impurities while crossing the cities. Since the river is slender in the cities due to concertized/solid embankment the flow is fairly fast. So, the whole material is pushed beyond the precincts of the cities. But as the river meanders beyond the city's ambit it spreads wider and slows down. So it gives enough opportunity to the colloids to settle down over some time the same enlarges to form River Island.

Confluence simulations based on dynamic channel parameters in the grasslands lacking historical measurements

Technology has greatly promoted ecohydrological model development, but runoff generation and confluence simulations have fallen behind in ecohydrological model development due to limited innovations. To fully understand ecohydrological processes and accurately describe the coupling between ecological and hydrological processes, a distributed ecohydrological model was constructed by integrating multisource information into distributed dynamic process model (DDPM). We mainly describe runoff generation and convergence modules. Based on the improved HBV model and degree-3 h factor method, runoff generation and snow routines were constructed for semiarid grassland basins. In view of meandering and variable steppe river channels and steep hydrological relief characteristics, a confluence module was constructed; the 1-km bend radius equivalent concept was innovatively proposed to unify river channel bend degrees. The daily runoff simulation validation results obtained using two datasets were R2 = 0.947 and 0.932, NSE = 0.945 and 0.905, KGE = 0.971 and 0.680. In the 3-hour flood simulations, the DDPM could better restore small long-distance water flows than the confluence method that did not consider actual river lengths or bend energy losses; the DDPM more accurately simulated the flood peak arrival time than the confluence method that did not consider overflow. The simulated mainstream overflow frequency increased by 0.84/10 years, and significant interaction periods of 10 to 13 years occurred with local precipitation, ecological status, and global climate change. An approximately 2-year lag occurred in the global climate change response. This study helps us further understand and reveal the ecohydrological processes of steppe rivers in semiarid regions.

Spatial and Temporal Characteristics of Channel Disturbance Zones in Big River, Southeast Missouri (1937-2018)

Ozarks watersheds have responded to land clearing and settlement disturbances by transporting large amounts of gravel and sediment to main valleys of medium-large river systems. Historical gravel and sediment accumulate in disturbance zones, which are areas of excessive channel activity that can be detected over time using historical aerial photographs. This project uses a series of aerial photos from 1937-2018 to identify disturbance zones in the Big River of southeast Missouri, which has a history of lead mining and ore processing that has caused widespread contamination of the channel and floodplain deposits. Variations in active areas of the historical meander belt show that disturbance zones account for 24 percent of the channel length at an interval of one per 2.5 km of channel. Megabars and extensions are the most prominent types of disturbance zones, but translations and cutoffs are larger with higher potential for sediment storage. From 1937 to 1976, areas of channel activity have cycled between expansion and contraction. However, after a period of recovery prior to 1976, disturbance zone areas have been expanding over the last 40 years likely in response to an increase in flood magnitude and frequency from more high intensity rainfall events since 1973.

Meander geometry characteristics as a response to hydraulic and lithologic control in the active floodplains of Lower Nagar basin

ABSTRACT The present work aims to evaluate the controlling factor of meander geometry in the alluvial rivers. The assimilation of lithologic and hydraulic analysis of the meandering channels puts new insight to the understanding of the meander geometry. The study compares two highly contrasting meandering rivers of Nagar and Kulik in the Lower Nagar Basin, India. To assess the connection between the meandering nature with the hydraulic and lithologic factors, extensive field survey was made during the bank-full monsoon period. The principal component analysis between the hydraulic variables and meandering components suggests that the hydraulic factors of Nagar more effectively control the bend structure of the river, whereas the lithology of the Kulik river controls the meandering planforms. The meander patterns have shown significant transition flowing over different lithologies of grainsize combinations. The statistical prediction based on the hydraulic functions was used to predict the future possible changes in meandering planform. Moreover, the implication of the result was validated with the past century changes and thus can be suitable for the river management practices. In general, the meandering dimensions (in terms of λ, Am and Rc) are found to be maximized when finer materials are prevalent and vice-versa.

Assessment of Groundwater Response Scenarios for Surrounding Areas After Filling the Proposed Badush Dam Reservoir, Northern Iraq

In the current study, the depth of groundwater was detected in (39) wells in the banks surrounding Tigris River between Mosul and Badush dams, and then the maps of depth and level of groundwater were drawn. To predict the response of groundwater behavior in the banks of Badush reservoir in the strips adjacent to the river when starting the filling process, the lines of selected water levels in Badush dam were plotted on the map of groundwater equipotential lines to detect the areas confined between the water level in the reservoir and the same level for groundwater. It is assumed that these areas are affected by the bank storage; therefore, they are prone to leakage or geotechnical problems within the zone of engineering facilities foundations including Badush Dam itself, the regulatory dam and infrastructure projects. In the pre-storage stage, it is noted that the area of influence of the bank storage is very limited and does not exceed 2 km2 on each side of the river in the area very close to the dam. When the water level raises more at the beginning of the storage, the area of influence of the bank storage will extend towards the upstream close to the river meandering. The effect on the eastern bank (left) will be wider compared to the situation in the western bank (right) where the effect is limited. The eastern side is characterized by having a higher population density and more urban establishments; therefore, the foundations of these establishments will be more affected. The area affected by the bank storage continues to widen towards upstream with the increase in the level of the dam reservoir until the effect reaches the maximum limit and approaches the shoulders of the regulatory dam, when the water levels in Badush reservoir are more than 245 m above sea level (a. s. l.). The variation in the groundwater extension effect with the continuous or gradual filling of reservoir requires monitoring and caution during filling, for fear of affecting the geotechnical properties of the soil and rocks within the foundations zone, and thus affecting the stability of the two dams.