Can an annual flood induce changes in channel geomorphology?

• Published in: Natural hazards (Dordrecht) Vol. 111; no. 1; pp. 1019 - 1046
• Main Authors: Islam, Aznarul, Sarkar, Biplab, Saha, Ujwal Deep, Islam, Mainul, Ghosh, Susmita
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.03.2022; Springer Nature B.V
• Subjects: Anthropogenic factors; Asymmetry; Channel morphology; Civil Engineering; Cross-sections; Depth; Earth and Environmental Science; Earth Sciences; Environmental Management; Floods; Fluid flow; Froude number; Geomorphology; Geomorphology of rivers; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Hydraulic radius; Hydraulics; Hydrogeology; Monsoon floods; Natural Hazards; Original Paper; Reynolds number; River channels; Rivers; Sand; Sandbanks; Width; Mayurakshi River; Hydraulic behaviour; Channel morphology; Sand mining; Fluvial architecture
• ISSN: 0921-030X; 1573-0840
• DOI: 10.1007/s11069-021-05089-7

The present study has been a pioneering effort examining the role of an annual flood as a potent stimulus inducing changes in channel geomorphology of the Mayurakshi River, India. Twenty cross sections have been considered for the measurement of various hydro-geomorphic attributes of the river in both the pre- and post-flood conditions in 2018. The study sensed an escalating trend for channel width, width/depth ratio, and wetted perimeter while the reverse was also detected for average depth, maximum depth, cross-sectional area, and hydraulic radius. For example, the width/depth ratio recorded an increase of ~ 11%, and the hydraulic radius depicted a decrease of ~ 8%. Furthermore, channel asymmetry, bed asymmetry and bed relief index experienced a decrease after the flood. The sudden hydraulic impulse during monsoon flood as manifested in velocity, discharge, specific stream power, Reynolds number, Froude number increases the erosivity of the fluid. Besides the hydraulic factors, bank material (massive sandbank susceptible to hydraulic action and mixed bank constituted by alternate bands of sand and silt, and vulnerable to failure by piping action) brings substantial changes in channel morphology. Moreover, anthropogenic interventions such as sand mining are found to play a significant role in channel behaviour. The role of the multiple factors driving the morphological changes of the cross sections has been unpacked using canonical component analysis.