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Geomorphological Studies from Remote Sensing
Published in Prasad S. Thenkabail, Remote Sensing Handbook, 2015
James B. Campbell, Lynn M. Resler
Channel migration describes the lateral movement of a river channel across the alluvial floodplain, through incremental erosion and deposition, and especially through avulsion—the sudden translocation of a river channel, typically in response to flood events. Understanding channel migration is critical dimension of addressing geomorphological and river management problems. Because of the large magnitudes and episodic and rapid rates of change, special surveillance systems are needed to efficiently measure and monitor channel migration. Because channel migration must be observed at rather broad scales, at infrequent intervals, RS forms an important tool for recording and analyzing channel migration.
Proposing BEHI-NBS method for the estimation of river bank erosion on a river in Nepal
Published in Silke Wieprecht, Stefan Haun, Karolin Weber, Markus Noack, Kristina Terheiden, River Sedimentation, 2016
River bank erosion or channel migration is a natural and geomorphic process of change in river resulted by adjustment of channel size and shape. Such changes are quite variable in space, depending in part upon position within the basin, and influenced by local variation in geology, soil, bank characteristics, vegetation, hydraulics, and other factors that influence vulnerability such as various types of land use (Aher et al. 2012). River changes in response to variation of variables like discharge and sediment supply (Mossa & Coley 2004). Rivers always tend to remain in the dynamic equilibrium state and to maintain this state, river balances its flow and sediment transport. In a free-flowing river system this equilibrium is always maintained by process of erosion and deposition (CRJC 1996). Bank erosion are special features of meandering river, where river channel migration takes place by erosion of the cut bank and deposition of eroded materials on point bar forming point bar deposit (Briaud et al. 2007, Das et al. 2014a). When river reaches lower reach, most of its erosive force concentrates to cut laterally hence, forming the meandering pattern (Das et al. 2014a). The migrating stream has tendency to widen the channel and erode the bank by undercutting its toe material and caving the bank (Baishya 2013). The fertile upland soil is then washed away by flow of the channel and deposited in the floodplain. These floodplain provides better yield and because of this benefit, these land are over cultivated, trees are cut down and cultivated field are poorly managed (Kaunda & Chapotoka 2003). Hence, destruction of flood plain and a reduction in the resource value of the river is associated with serious bank erosion (Thorne 1999).
Process-based approach on tidal inlet evolution – Part 1
Published in C. Marjolein Dohmen-Janssen, Suzanne J.M.H. Hulscher, River, Coastal and Estuarine Morphodynamics: RCEM 2007, 2019
D.M.P.K. Dissanayake, J.A. Roelvink
It was concluded that the channel migration processes are triggered by bend erosion and floodplain crevassing. Furthermore, bar channeling along rills formed by sand fluidization – during low-water stages – could be a significant mechanism of the main channel relocation during the period of rising water stages.
An automated approach in estimation and prediction of riverbank shifting for flood-prone middle-lower course of the Subarnarekha river, India
Published in International Journal of River Basin Management, 2021
Subsequent flood-induced channel migration causes diverse natural and socio-economic hazards in terms of flood hazard, loss of riparian arable land and crop damage, sand deposition over arable land, compensation of customary dwellers and casualty. In the years of 1950, 1960 and 1971, the large-scale bank erosion and channel shifting took place due to the catastrophic flood in the middle-lower course of the Subarnarekha River. For instance, the advent of 1971 flood rubbed out the settlements of the Gokulnagar and Kamalapur villages (Nayagram block) at the right bank margin of the river course (zone B) with an average 900 m leftward riverbank shifting. Thus, the bank margin allows leftward shifting the course and formed a dry gap with shrubs and grasses at the place of the former active channel. Also, near Ashui (at Gopiballavpur II block of zone A), the right bank has shifted about 250 m on the landward side (rightward) and 1 km distance along the bank through eroding agricultural land and embankment breaching. However, after 1971, the bank shifting nature has changed with due effects of high magnitude floods in the years of 1972, 1989, 1990, 2000, 2005, 2008, 2013 and 2014, and moderate–low magnitude floods in the other years (during the considered period). The areas eroded by the 1971 flood somehow modified with the sediment accretion process in the different channel reaches. Such a condition is approved by the LRR and EPR model-based riverbank shifting. During 1973–1990, the left bank of the meander L1 and L2 and right bank of the meander R1 are shifted with an average distance of 350 and 300 m toward the right and left, respectively. Moreover, about 350 m leftward shifting is observed at the crest position of the meander bend R3. Near the Rajghat and Baliapal, the left bank shifts with an average accretion of 650 and 1250 m, respectively. Although, the erosive nature (about 720 m) is also observed at the right bank of the L12 meander bend near the Chaumukh section. In the later phase, during 1990–2015, only some sectional channel reaches have experienced with a significant level of accretion. However, these accreted stretches were remained as a part of the active channel during the 1970s. The abundant amount of channel shifting is experienced at the meandering stretch of the Baliapal section (Figure 13) with natural adjustment of the meandering channel pattern. Moreover, during 2014–2015, just 850 m upstream position of L1 meander, the right bank (near Athangi village, Gopiballavpur I block) eroded about 750 m rightward through eroding the bank margin agricultural land. Moreover, the tidal turbidity current is responsible for the riverbank shifting of the tide-dominated lower course (zone D). The impact of large floods on riverbank erosion and accretion, sand mining from bank margin riverbed and erosion protection embankment structures at different river stretch has resulted through the EPR model-based bank shifting analysis.