Estimating flow properties of quasi-newtonian mass-movements

A variety of models exist in the literature to describe the flow behavior and rheological nature of debris flows. These include viscoplastic models, inertial grain flow models, fluid-solid momentum transport models and empirical Chezy-type models. For the purpose of planetary studies, the Chezy-type models have been found very useful. These models make few apriori assumptions on the physical processes ongoing in a debris flow, but rather parameterize the momentum transport and energy dissipation of debris flows with semi-empirical constants. When properly calibrated with appropriate field and laboratory evidence, these constants can provide a first order qualitative view into the behavior and rheological character, particularly water content, of a debris flow. Such a view permits the development and use of the more sophisticated debris flow models mentioned above where the physical processes are explicitly accounted for and from which, in conjunction with observation, quantitative rheological parameters can be determined. The strength of the Chezy-type models lies in that its parameterizing constants can be derived relatively easily from topographic data and airborne or space-based imaging and compared with a large body of terrestrial analogs. In this study, we will use a form of the Chezy model commonly applied to investigate quasi-Newtonian flows that are fast moving fluids bearing various kinds of loading or suspension. We will present a list of the Chezy constants for a wide-range of debris flows, ranging from water to water-rich landslides. This calibration table was determined by completing a literature search where velocity, channel slope, channel cross-sectional area, channel width and rheological characteristics of the debris flows were available. We show how rheological inferences, particularly water- content of one type of mass movement - debris flows - can be constrained using planetary data sets. These inferences are derived through judicious use of topography, imagery, field experience and geomorphology. Our analysis will include a discussion of the advantages and limitations of the Chezy model, as well as identify some of the pitfalls that may occur in a typical analysis.