Understanding dynamics of wet granular flow-induced erosion and sediment entrainment on Narmada sand beds at lab scale

Abstract

The entrainment of erodible beds under wet granular flows is a fundamental process with significant implications for sediment transport and erosion dynamics. Lab-scale flume experiments are useful for understanding flow behavior

however, constructing erodible beds poses challenges, as their preparation must be carefully controlled to capture the complexity of natural conditions. This study investigates the entrainment behavior of wet granular flows over erodible beds of Narmada sand under varying bed angles (22°, 27°, and 32°) and water content (20–50 %). To achieve consistent erodible beds, a mist pluviation technique was adopted, ensuring reliable preparation that underpins the validity of our experiments. Controlled flume experiments were conducted to systematically evaluate the influence of bed slope and flow composition on erosion and deposition processes. The study shows that entrainment is predominantly governed by collisional stresses, strongly influenced by flow-front velocity, bed slope, and water content. At higher bed angles (32°), entrainment was more pronounced along the downstream end of the bed due to increased flow momentum, while lower slopes (22°) exhibited maximum erosion in the middle sections. Volumetric water content (w/c) of granular flow significantly influenced the entrainment pattern, with a parabolic relationship observed between entrainment rate and volumetric w/c of erodible bed. Our research findings demonstrate how properties such as water content, and slope angle directly influence erosion thresholds and entrainment depth. These quantified relationships provide critical input for sediment transport models. © 2025 Elsevier B.V., All rights reserved.