NEWTONIAN FLUID-MECHANICS TREATMENT OF DEBRIS FLOWS AND AVALANCHES

Calculations are carried out first for steady fully developed laminar flow on a slope. Application of this result to field data published in a previous paper by another author suggests that many debris flows are laminar. Then singular perturbation techniques are used to obtain first-order solutions for unsteady nonuniform flow from a point source on a steep slope. Solutions are obtained for both laminar and turbulent flows, and it is found that the laminar flow model gives the best description of laboratory data obtained by a previous investigator. A number of differences are observed in the behavior of the outer (kinematic wave) solutions for laminar and turbulent flow, and it is suggested that it is probably not possible to describe all debris flows and avalanches with laminar now models. It is also suggested that more comparisons need to be made between theoretical results and field data measurements.