ABSTRACT
The watershed boundary outlines the hydrologic system within which all living things are inextricably linked by the common waterway. Watershed is also called basin or catchment. A watershed is defined by its boundaries that can be delineated from the topographic maps and then verified by field inspections. Watershed area is the most important parameter to select a proper hydrologic method for flood flow predictions. The length of a waterway has a direct impact on the flood wave travel time through the watershed. Waterway slope is an important factor in determining the water flow velocity. The basic principle of flood routing is to solve the continuity principle with consideration to the change in the storage volume. Based on the surface textures, a watershed is divided into impervious and pervious areas. The major hydrologic losses considered in the rainfall and runoff modeling techniques include vegetal interception, depression storage, and soil infiltration.
