Study of the maximum 24-hour rainfall to estimate the maximum probable flood in the basin Ajay Chai using the HEC-HMS model

Estimation of design flood is important components of hydrology studies, water resources projects and especially dam construction projects. Design of a flood barrier, is formed by a peak flood, volume and period appropriate to the dam safety and related structures during the operation ensures. Probable maximum flood would have taken if all physical, hydrological and meteorological factors had existed in a region. In This study in order to estimate PMF of the Ajichay basin, we have used HEC-HMS model from precipitation runoff mathematical models. Purposes were collected meteorological, synoptic and rain gauge data related to 40 stations from Meteorology and Tmab Company. In order to estimate probable maximum flood, the main basin were divided to smaller sub basin and then were determined physiographic properties in each basin. Rainfall pattern was selected 24- hour rainfall based on type II pattern and the largest 6-hour rainfall was extracted in different return periods. Then HMS model was applied in order to create hydrographs of probable maximum flood at different return periods and hydrographs of probable maximum flood were drawn for various sub basins. Probable maximum flood were calculated for all sub basin. Total Probable maximum flood was estimated at return periods of 2, 10, 25, 50, 100 and 200 years, respectively, 18261, 33073, 42212, 49207, 55845 and 62198 Cubic meters per second in Ajichay basin.