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Temporal variation of braided intensity and morphodynamic changes in a regulated braided river using 2D modeling and satellite images
  • Behnam Balouchi,
  • Nils Rüther,
  • Kordula Schwarzwälder
Behnam Balouchi
Norges teknisk-naturvitenskapelige universitet

Corresponding Author:behnam.balouchi@ntnu.no

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Nils Rüther
Technische Universitat Munchen
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Kordula Schwarzwälder
Norges teknisk-naturvitenskapelige universitet
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The river morphology of a braided-type river is rather complex. High sediment transport rates and frequently changing discharges are the cause of dynamic planform evolution. Over the past few decades, scientific attention has been directed toward understanding the coexistence of alternating bars and the consequent emergence of confluences and divergences, all of which interact intricately with the process of bank erosion. It is still rather challenging to estimate or predict the total sediment transport rate in such type of rivers, especially by considering various hydrologic data and climate effects. This study is focused on a reach of the Devoll River in Albania, located upstream of the Banja dam. Understanding the morphodynamic of this river reach holds significance due to the expanding delta upstream of the dam reservoir. The objectives of the two-dimensional (2D) depth-averaged approach of the present study are to investigate the temporal variation of braided intensity of Devoll River due to using a discharge hydrograph from hydrologic data compared to the regulated one from the upstream dam on the morphodynamic of the river, and estimate the sediment transport rate of this complex braided river. After evaluating various parameters such as 11 different sediment transport functions, the best results were reached for a cell size of 5×5 m 2, Manning roughness coefficient of 0.03, Meyer-Peter and Müller’s sediment function, Hayashi et al. (1980) hiding function, and Van Rijn bed roughness predictor in this study. In addition, the results of comparing satellite images and modeling the river from 2019 to 2023 show that the braided index (BI) decreased, and this can be due to the fact that the real scenario of the river has a regulated discharge (scenario A) compared to the non-regulated discharge of hydrologic data (scenario B), in the mentioned period. Moreover, the study also estimates sediment transport rates, with scenario A showing higher values for total bed load rate (35.93 kg/s/m) and suspended load concentration (652.48 mg/l) compared to scenario B (16.32 kg/s/m and 152.39 mg/l). This research highlights the impact of regulated discharge on sediment transport in a complex braided river.