Characteristics of thalweg profile and cross-sectional geometry along alluvial river bends

Abstract

ABSTRACT River bends have always drawn attention for their complicated hydraulic, geometric and migration nature. Laboratory as well as field experiments have been carried out to study the geometric behaviour of channel bends. This study aims to analyse the nature of the thalweg profile, longitudinal and transverse slope and distribution of depth in the cross-sectional geometry of both single and consecutive double bends of the channel. In the single bend, the thalweg approaches to the outer bank and becomes closest after the apex of the bend whereas in the successive bends of a double bend, the thalweg is closest before the apex of the bend. These results indicate that the thalweg of a bend depends on the previous consecutive bend. The longitudinal slopes vary periodically along the river bend creating the deepest pool before the apex of the bend. The centre line transverse slope varies periodically; however, the outer transverse slope with respect to the thalweg is maximum where the thalweg is closest to the outer bank. The thalweg and outer quarter line to centre line depth ratio is higher before the apex and reduces after the apex of the bend. The inner quarter line to centre line depth ratio varies periodically with a relatively smaller amplitude.