| Abstrakt: |
This study aims to analyze the impacts of anthropogenic interventions on channel planform adjustments of the sub-Himalayan Mahananda-Balason River system for 52 years (1968–2020). In the studied period, Siliguri, a small urban sprawl, has largely grown to the 3rd largest in West Bengal, India, just after Kolkata and Asansol and, alongside with this the studied river system, flowing through Siliguri urban region, has adjusted its planform largely. Now, this study is chiefly framed to study the interrelationship between these. A total of 6 satellite images (1968, 1979, 1989, 1998, 2008, and 2020) have been used to measure anthropogenic interventions that include embanking, sediment extraction, land use changes, longitudinal obstructions, and channel planform properties comprising channel width, area, length, bar coverage, and channel pattern. All these quantifications are done reach-wise as both the river systems, that is, Mahananda and Balason, are sub-divided into 5 equidistant reaches each. Considering the nature of the generated data structure, initially, a two-tailed "t"-test was performed to measure the statistical significance of the change rate of the indicators followed by the panel data regression using the fixed effect model (FE) to measure the intensity of ongoing alterations on channel planform adjustments. Results showed that, with significantly increasing urbanization, embanking and in-channel sediment extraction, channels get narrowed by > 50%. Alike to channel width, the channel length and bar coverage were also reduced in reaches 2–5, and reaches 7–9. Ultimately, the inherent braided nature of the channel planform had adjusted largely and even transformed sinuous (reaches 3, 4, 9, and 10). Obtained R2 values inferred that the anthropogenic interventions were highly responsible for such intensive channel adjustments. Relatively, upper reaches (reaches 1 and 6), having fewer human interventions, are still managing their pre-existing channel morphology, although undersupply of sediments at the lower reaches and gradual engulfment of rural areas adjacent to upper reaches for urbanization is driving these reaches towards adjusting their channels accordingly. An economically viable and robust assessment like this is needed to prevent the possible undersupply of riverine resources and to develop policies on its sustainability. Such studies are immensely suitable in data-scarce regions also where investigations do not take place in the past and secondary data are also inadequate. [ABSTRACT FROM AUTHOR] |
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