Prospects of Modeling and Morpho-dynamic Study for Brahmaputra River
01 Jan 2017-pp 189-209
TL;DR: In this article, a 2D enhanced numerical model with boundary-fitted coordinate system for a braided stretch of the Brahmaputra River has been developed and verified for better and more realistic flow field assessment.
Abstract: The Brahmaputra River in the Northeastern State of Assam in India is characterized by its exceedingly high discharge with enormous sediment load, spatio-temporal variation in channel morphology, substantially high bed aggradations, and severe bank line erosion. The river maintains almost continuous channel braiding in most of its segments in the alluvial floodplains of Assam. One-dimensional (1-D) flow models are insufficient to tackle problems of braided streams due to lack of information with regard to transverse flow field. Hence, for better and more realistic flow field assessment, two-dimensional (2-D) or three-dimensional (3-D) numerical models are to be used. 3-D models are numerically too expensive for macro scale river reaches. Hence, 2-D enhanced model with secondary flow corrections in governing equations may be used. After successful implementation of 1-D mathematical model for a braided stretch of Brahmaputra River, 2-D enhanced numerical model with boundary-fitted coordinate system for the same stretch has been developed and verified. A new planform index is proposed namely braid power. It increases with decrease in incoming discharge into the reach in a particular instance of time. The measured braiding indicator, namely, Plan Form Index (PFI) using high-resolution satellite data application, is found to be quite useful for the monitoring and analysis of persistent and complex braiding behavior of a large river like the Brahmaputra. The erosion study based on satellite data based analysis conclusively identifies three to four major geological channel nodal points present along the Brahmaputra River. The variability of stream power with bank erosion and braiding process is investigated. A distinct behavioral pattern between these is observed. For example, with low stream power, braiding appears to intensify which in result may reflect a higher possibility of bank erosion.
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TL;DR: In this article , the authors synthesize the knowledge on braided rivers and an extensive review of the bio-morphological processes in the Brahmaputra River and integrate field investigated datasets along with geo-spatial imageries and Google Earth Engine computed fluvial information to conceptualize and understand the complex underlying processes.
Abstract: The spatio‐temporal heterogeneity in process–form–vegetation interactions has enabled the Brahmaputra river system to dissipate the fluvial energy at hierarchical scales. The present review article synthesizes the knowledge on braided rivers and an extensive review of the bio‐morphological processes in the Brahmaputra River. In addition, field investigated datasets along with geo‐spatial imageries and Google Earth Engine computed fluvial information are integrated to conceptualize and understand the complex underlying processes in the river. The review can be further used to propose rejuvenation frameworks and research directions concerning the implication of hierarchical energy dissipation potential in the Brahmaputra River.
4 citations
TL;DR: In this paper, the long-term temporal trends of temperature, precipitation, extreme climate indices, and river discharge were calculated to assess the variations and patterns of hydro-climatic variations in the urban watershed of Guwahati from 1991 to 2019.
Abstract: The urban watershed of Guwahati situated on the bank of the Brahmaputra River is one of the fastest growing cities of India. During the last two decades, water security concerns due to climatic variabilities have become a pronounced issue in the urban watershed of Guwahati. Thus, the study aims to calculate the long-term temporal trends of temperature, precipitation, extreme climate indices, and river discharge to assess the variations and patterns of hydro-climatic variations in the urban watershed of Guwahati from 1991 to 2019. Furthermore, the current study also tries to correlate these extreme climatic indices to river discharge to determine the degree of hydro-climatic variations. The Mann–Kendall statistical techniques and Sen’s estimator were used to calculate the statistical significance, stability, and averaged magnitude of trends in the hydro-meteorological data. The result shows that the wetness indices, R20 and RX5Day, reported a decline in Guwahati’s urban watershed from 1991 to 2019, resulting in a reduction in intensity and duration of heavy rainfalls while the dry spell (CDD) has been more distinct in the study area with a rise in the average temperature by 0.023 °C/year. Similarly, the most significant statistical trend was found in the monsoonal discharge of the Brahmaputra with a negative trend of − 204.16 m3/s/year. The results also show that fluctuations in rainfall patterns have a direct impact on the discharge of the Brahmaputra. These phenomena can affect the quantity of river water resulting in a severe impact on water security in the study area.
4 citations
References
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TL;DR: In this paper, a methode numerique par volume fini pour the resolution des equations de Navier-Stokes bidimensionnelles, incompressible, and stationnaires, en coordonnees generales curvilignes, is presented.
Abstract: Presentation d'une methode numerique par volume fini pour la resolution des equations de Navier-Stokes bidimensionnelles, incompressibles, et stationnaires, en coordonnees generales curvilignes Application de la methode aux ecoulements turbulents sur des profils avec et sans separation au bord de sortie posterieur Comparaison des calculs avec des donnees experimentales
4,356 citations
TL;DR: The research included pre—settlement vegetation reconstruction based on the General Land Office survey notes, a statistical comparison between historic rates of woodland expansion from aerial photographs and environmental variables, and a field study of seedling demography to isolate the factors controlling recruitment and survival in the modern river.
Abstract: This research was conducted to identify the factors that have permitted Populus—Salix woodland to expand into the formerly active channels of the Platte River and its two major tributaries, the South and North Platte rivers. The research included: pre—settlement vegetation reconstruction based on the General Land Office survey notes, a statistical comparison between historic rates of woodland expansion from aerial photographs and environmental variables, and a field study of seedling demography to isolate the factors controlling recruitment and survival in the modern river. Woodland expansion began in the South and North Platte rivers around 1900 and spread downstream into the Platte River. By the late 1930s, vegetation had occupied most of the former channel area of the South and North Platte rivers and was expanding into Platte River channels. Rates of channel loss in the Platte River have been as great as 10%/yr during droughts. By 1986, channel—to—woodland proportions were relatively uniform throughou...
541 citations
Book•
01 Jan 2020
TL;DR: In this article, the fundamentals of modeling flow and sediment transport in rivers are presented, treating both physical principles and numerical methods for various degrees of complexity, including 1-D, 2-D (both depth and width-averaged) and 3-D models.
Abstract: Comprehensive text on the fundamentals of modeling flow and sediment transport in rivers treating both physical principles and numerical methods for various degrees of complexity. Includes 1-D, 2-D (both depth- and width-averaged) and 3-D models, as well as the integration and coupling of these models. Contains a broad selection
409 citations
TL;DR: Bar formation and sediment distribution patterns were examined in a 4-mile braided reach of the upper Kicking Horse River at Field, British Columbia, which was mainly supplied by meltwater from icefields straddling the continental divide at the British Columbia-Alberta boundary in the southeastern Canadian Cordillera as mentioned in this paper.
Abstract: Bar formation and sediment distribution patterns were examined in a 4-mile braided reach of the upper Kicking Horse River at Field, British Columbia, which is mainly supplied by meltwater from icefields straddling the continental divide at the British Columbia-Alberta boundary in the southeastern Canadian Cordillera. Marked diurnal variations in discharge, suspended sediment concentration, and water temperature occur during peak summer melting periods when rates of sediment transport and bar formation are greatest. Bed material is mostly limestone and dolomite gravel which undergoes rapid fining in the downstream direction. Gravel bars occurring in a wide variety of shapes and sizes comprise the dominant bed forms. Most exposed braid bars have undergone complex depositional and erosional histories and rarely show simple or consistent patterns of grain size or structures, either internal or superficial. Active bars with simple histories and predominantly depositional morphologies are termed "unit bars." Fo...
370 citations