Assessment of meander‐bend migration of a major distributary of the Ganges River within Bangladesh

Abstract

The Arial Khan is an important distributary river of the Ganges River within Bangladesh. The river is meandering, and channel shifting and bend migration are common. This study investigates the bend‐scale morphology of 37 characteristic bends of the river using Landsat imageries, river bathymetries, and hydrological data. The morphological changes of the river are correlated with the temporal shifting of its offtake, which in turn is linked to the dynamic behavior of the river in terms of sinuosity, bend geometry, and bend migration. Alterations in the offtake location, bed elevation, and in‐front bar formation are found to control the flow to the river. The sinuosity varies from 1.62 to 1.95 and is linked to the shifting of its offtake. The lifetimes of the bends increase from upstream to downstream with an average lifetime of 24 years. The radii of the bends vary from upper to lower reaches with an average radius of 921 m. The upper reach is more migration prone, and its average migration rate (108 m/year) is more than twice the other two reaches. A higher migration rate of 70–80 m/year is found for the river during 1981–1999 compared to the rates of 45–50 m/year for the rest of the study periods (1972–2021). An envelope curve depicting the relation between the relative curvature of a bend and its migration rate for the river is also developed. The overall morphology from 1972 to 2021 indicates that a significant increase in sinuosity and a reduction in river width and aspect ratio have occurred. The migration rate has declined slightly and the frequency of bend cutoffs has reduced notably in recent years. Nonetheless, due to the high rates of migration, there exists potential future threat to riverbank erosion in some critical bends, and hence damages to land, property, structure, and project on the vulnerable banks.

Effect of water depth and waterway obstructions on the divergence and confluence areas of Dongting Lake and the Yangtze River after the operation of the Three Gorges Project

“…The continuous curved river has wandering characteristics, and the plane position of the river changes greatly (Ferdoush et al, 2022). From 2012 to 2021, the Xiongjiazhou–Chenglingji reach in the inflow area of Dongting Lake was characterized by “scouring of point bars on the convex bank, and sedimentation of the river channel on the concave bank” (Figure 11a).…”

“…With the decrease in the Ouchikou diversion, the relative increase in the runoff of the Jingjiang reach caused the collapse of the right edge of Tianxingzhou and the erosion of the upper section of the Tuoyangshu point bar, consequently affecting channel conditions in the downstream reaches directly (Figure 10a The continuous curved river has wandering characteristics, and the plane position of the river changes greatly (Ferdoush et al, 2022). From 2012 to 2021, the Xiongjiazhou-Chenglingji reach in the inflow area of Dongting Lake was characterized by "scouring of point bars on the convex bank, and sedimentation of the river channel on the concave bank" (Figure 11a).…”

Integrated assessment of flood risk in Arial Khan floodplain of Bangladesh under changing climate and socioeconomic conditions

“…This causes severe hardship for the people living in the floodplain (Tingsanchali & Karim, 2005). The morphological processes and instabilities of the Arial Khan River have been the subject of a few studies (Akter et al, 2013; Ferdoush et al, 2022; Mamun, 2008; Winkley et al, 1994). The flood danger level of the river at the Madaripur gage station (SW5) is 4.20 m above the public works datum (PWD), which is crossed frequently during the monsoon.…”

Flow patterns at river bends and its response to surrounding infrastructures

“…This study focuses on the flow characteristics and changes in river morphology at the river bends. Changes in river morphology, especially at bends, will mostly affect the surrounding environment [13].…”