This book describe the modeling approach for the flood flows for gauged and ungauged catchments. This book comprise of modeling approaches of intensity duration frequency curve, unit hydrograph, geomorphologic instantaneous unit hydrograph, rainfall excess computations, parameter estimation, hydraulic modeling, etc. Apart from this, application of Geographic Information System (GIS) in surface hydrology is described in the book. This book will provide the good understanding of using the hydrologic models for estimating the flood flows. For replication of the approches, computer programmes appended in the book will be very helpful to users. This book will be beneficial to the hydrologist, researchers, civil and agricultural engineers.