Study of contribution role of sub-basin in intense flooding;

One method of decreasing loss resulted from flooding is to determine flood productive regions and applying appropriate methods to control flooding. In this study، by using HEC-HMS model accompanied by GIS technology the contribution rate of different sub-basins located upstream of Chamchit hydrometry station in Dalaki basin based on 2،50 and 100 years return period is determined. In this research upper sub-basins of Chamchit hydrometry station ranked due to flooding using Single Successive Subwatershed Elimination method in HEC-HMS environment. Results of this study showed that sub-basin contribution rate in whole output not only affected by area and peak discharge of sub-basin but also factors like location of sub-basin، distance from output، CN، and Flood Routing role in main river have significant impact on the portion of sub-basin in production of the whole basin flood (sub-basin flooding). Except above mentioned، it was found that there is no significant change in sub-basin flooding priority in different return periods.