mass movement of material mostly finer than sand, along with some rock debris, lubricated with large amounts of water. The water tends to make mudflows move faster than earthflows or debris flows.
A well-mixed mass of water and alluvium which, because of its high viscosity and low fluidity as compared with water, moves at a much slower rate, usually piling up and spreading over the fan like a sheet of wet mortar or concrete. (Woolley, 1946, p. 75.)