A two-dimensional layer-averaged Bingham fluid numerical model has been used to explore the relative importance of yield stress, kinematic viscosity, bottom slope and initial failure height on the run-out distance of debris flows. The parameter ranges used include low values that are appropriate to marine conditions where debris flows can travel large distances on very low slopes. The sensitivity analyses demonstrate that the yield stress exercises much more control than the viscosity, especially within the value ranges that are often used to simulate the formation of marine debris flow deposits. In practice, low values of the Bingham fluid parameters are used in numerical simulations of observed deposits to compensate for a number of detailed flow phenomena that are not included in the model. These processes are described, and recommendations are made for including them in future models.