Physical modelling to map the rheological and morphological dynamics along with entrainment mechanics of debris flow: a comprehensive review of the state of the art

Abstract Introduction Debris flows are climate change-driven geohazards that pose a significant threat to life and the built environment. These flows are unconfined, in which the water-laden mass comprising of soil, gravel, boulders, and trees surges down steep hill slopes and channelises into streams, trapping everything that encounters them. These hazardous flows impact the engineering and defence structures, transportation systems, and the environment. State of Knowledge Various researchers have performed numerous laboratory-to-field scale experiments to understand debris flow's dynamic morphological and rheological properties. The state-of-the-art approach to evaluating the effect of multiple factors, such as water content, pore water pressure, grain size distribution, topography, solid volume fraction, and basal friction parameters on the initiation mechanism, dynamics, and morphology, has evolved rapidly in the past few decades. Objective The present paper discusses the progress in the identification of rheological and morphological characteristics of the debris flow and the advancement in debris flow experimentation. Approach and Scope This review will help the readers get a consolidated overview of the recent advancements in debris flow experiments. The study complements the previous studies by identifying the latest developments in debris flow experiments, such as the effects of material and geometric parameters on flow dynamics, mechanisms of evolution of excess pore water pressure in saturated and unsaturated bed conditions, entrainment mechanisms, and the classification of experiments based on the type and size of experimentation. Discussion and Relevance The characteristics of debris flow are also discussed based on different phases in debris flows, such as the initiation phase, dynamic phase, morphological characteristics, and impact on the built environment.