Geophysical mass flows, such as landslides, avalanches or debris flows, are frequent mass movement processes in mountain areas and often cause disastrous damage. This book lays a foundation for formulating the depth-averaged equations describing the shallow geophysical mass flows over non-trivial topography. It consists of the detailed derivation of the model equations. The stimulating numerical examples demonstrate how the proposed models are applied. All this make this book accessible to a wide variety of readers, especially senior undergraduate and graduate students of fluid mechanics, civil engineering, applied mathematics, engineering geology, geophysics or engineers who are responsible for hazard management.