Morphology of the Kosi megafan channels

Kumar Gaurav (1) , François Métivier (1) , Olivier Devauchelle (1) , Rajiv Sinha (2) , Hugo Chauvet (1) , Morgane Houssais (3) , Hélène Bouquerel (1)

1 IPGP - Institut de Physique du Globe de Paris
2 IIT Kanpur - Indian Institute of Technology Kanpur
3 Levich Institute

We report on a new set of measurements on the morphology of braided and meandering threads of the Kosi megafan, North Bihar, India. All threads develop on a uniform sandy sediment and under a similar climate. The data set is composed of the width, depth, water discharge and grain size of 51 threads. Downstream slopes and sinuosity are also available. Using this data set, we show that braided and meandering threads share common hydraulic geometries. We then use the threshold theory to explain why the aspect ratio of threads is almost naturally detrended, and rescale the data according to this theory. As expected, the rescaled dimensions of braided and meandering threads are weakly correlated to water discharge. We propose that the large dispersion observed, which is common to meandering and braided threads, is the signature of sediment transport, vegetation or cohesion effects.

Domaines: Géomorphologie

Kumar Gaurav, François Métivier, Olivier Devauchelle, Rajiv Sinha, Hugo Chauvet, et al.. Morphology of the Kosi megafan channels. Earth Surface Dynamics, 2015, 3 (3), pp.321-331. ⟨10.5194/esurf-3-321-2015⟩. ⟨hal-01499419⟩