اثر ارتقاع بر بارندگي هاي يك روزه سيل زا براي برآورد دبي اوج در حوزه آبخيز سد سفيدرود

Effect of Altitude on Daily Flooding Rainfall for Estimation of Peak Flow

One of the most important factors which affect the flooding behavior in every watershed is high rainfall. The daily rainfall data are the most available data with non-linear mathematical relations (between daily rainfall and short duration rainfalls) having been established and accepted in Iran. If there existed some relationships between daily flooding rainfall and altitude, the creating of precise mathematical models would be possible. Such asituation will facilitate precise estimation of peak flows. In this research 262 hydrographs were selected in three subwatersheds and their corresponding daily rainfal data extracted from 38 raingauges scattered all over their areas. The correlation cofficience between altitudes for raingauges and daily flooding rainfalls indicate that there are direct correlation at a confidence level of 1% for two watersheds and at 5% for others. Also the correlation between coefficient of variation (CV) in daily flooding rainfalls and altitudes were significant by linear negative regressions at a confidence level of 1% in one subwatershed and at 5% for others. Also the correlation between peak flows of hydrographs and corresponding daily flooding rainfalls was significant at a confidence level of 1% in all subwatersheds. This research indicated that introducing altitude as a variable factor in producing mathematical equations for short duration rainfalls (from daily rainfalls) can help improve the models of estimation of peak flows at ungauged watersheds.