This book presents the mathematical modeling aspects of rainfall-runoff-erosion processes in the watershed, in which the watershed''s hydrodynamics and erosion process were suitably considered using the kinematic wave with variable overland resistance, and upland erosion model, respectively. To account for the infiltration process in the watershed, parametric two-term Philip model was applied. Further, to generalize the application of the process-based model, this model was extended for the ungauged watersheds. This book also comprise of several monograms developed from the analysis of various watersheds of different geophysical characteristics for ready reference to the field engineers. This book will be especially helpful to the scientists, engineers, researchers working in the field of hydrology, watershed management and hydrological design.