This volume discusses the general physics of debris flows and various approaches to modeling - including the SEGMENT-Landslide approach - as well as the pros and cons of these approaches and how other approaches are sub-sets of the SEGMENT-Landslide approach. In addition, this volume will systematically unify the concepts of vadose zone hydrology and geotechnical engineering, with special emphasis on quantifying ecosystem consequences of storm-triggered landslides in a warmer climate setting. The reader will find a comprehensive coverage of concepts ranging from hillslope hydrology, porous granular material rheology and the fundamentals of soil properties, to state-of-the-art concepts of enhanced hydrological cycle with climate warming and a discussion of new approaches for future research.