Mostafa Aram - MS.c student of Watershed Management. Yazd University, Iran.
Abghari Hirad - Assistant Professor, Faculty of Natural Resources, Urmia University, Iran.
Hossein Malekinezhad - Assistant Professor, Faculty of Natural Resources Yazd University, Iran.

Estimation of Peak flow discharge is an important subject in the watersheds modeling, Increases of population and urbanization development leads the increasing of human usage of water systems. considering the development of construction affecting watershed hydrologic responses. Therefore, in this study, we evaluate these effects on hydrologic responses base on peak hydrograph of Castro watershed located in North California. The date that selected was 16 January 1973 rainstorm recorded in the outlet. In order to estimate losses, excess runoff and loose flow in the Hec-Hms Hydrologic Model primary constant, Snyder’s Unit Hydrograph and Current Recession methods are used. Results shows that urban development leads to at least 2% increase in peak hydrograph as changes in infiltration Coefficient and time to peak of the floods.

HEC-HMS, Castro Strait watershed, Urbanization. Rainfall- Runoff Modeling