Dynamics of meander geometry and formation of neck cutoff of River Raidak-I within Himalayan foreland basin, India

Tectonic activities and catastrophic flood events significantly assist to the process of channel avulsion and formation of river cutoffs on alluvial floodplain. The principal objectives of this research are (i) to examine the mechanism and causes of neck cutoff formation of river Raidak-1, India applying geospatial techniques, old maps and bank facies (1955-2019) and (ii) to investigate the dynamics of meander channel geometry using fluvio-hydrological techniques. Geospatial techniques and field based bank facies analysis have been used in this study. The result showed that the river channel has been significantly shifted (during the time span 1955-2019) owing to lateral channel migration resulting into formation of several neck cutoffs on the floodplain. Meander geometry study revealed that radius of curvature, meander wavelength, meander amplitude and meander belt width have been fluctuated during the entire study periods. The threshold value (less than 5 degrees ) of apex angle of two tangents at meander loop and neck distance (less than 1 km) helps to form regular neck cutoffs. The results show that high sinuosity, threshold value of meander loops; major flood events, high discharge and non-cohesive bank materials are responsible for the development of neck cutoffs. Moreover, probable sites of future cutoff formation have also been identified. Therefore, this study would give proper insights for river management approach particularly on dynamic Himalayan foreland basin, India.