Modeling Subaqueous and Subaerial Muddy Debris Flows

Debris flows are notorious geohazards existing in both subaerial and subaqueous environments. They may cause catastrophic destructions to adjacent life and properties along their overriding path. As such, predictions of their movement are critical to future geohazard mitigations, and there is a need to develop an effective numerical model to achieve this purpose. In this paper, a two-dimensional depth-averaged numerical model is presented to simulate the movement of subaqueous and subaerial muddy debris flows. The Herschel-Bulkley rheological model is used to describe the rheology of debris flow. The conservation equations of mass and momentum in conservative forms are numerically solved using an explicit finite difference scheme. The model is applied to a series of one-dimensional laboratory experiments in subaerial environments. The model is also applied to a field setting within the Na Kika Basin, Gulf of Mexico. Modeling results of deposit thickness of debris flow agree with those laboratory and field observations. Furthermore, the model is applied to two synthetic two-dimensional field conditions, one with a uniform slope and the other with a sinuous canyon. Sensitivity analyses are performed to explore the relative importance of yield stress, dynamic viscosity, bottom slope, initial failure height, and initial failure shape for runout distances of debris flow. For the application with a sinuous canyon, two different dimensions of canyon are used to demonstrate possible deposition patterns of debris flow.