Applying a Graphical Method in Evaluation of Empirical Methods for Estimating Time of Concentration in an Arid Region

At gauged watersheds, the time of concentration can be estimated using rainfall-runoff data; however, at ungauged empirical methods are used instead. Large errors in application may cause inaccurate modeling floods and unreliable structure design. In this paper, for calculating (Tc) were compared to identify best equation estimating Tc watersheds an arid region. The graphical method, based on measured data, was 15 determine which method returned results. applied 33 events four rural sub-watersheds located central parts Hormozgan province, Iran. A ranking-based procedure select performing methods. To minimize bias improve accuracy, modified by adjusting their formulas. According study, three methods: (1) Williams, (2) Pilgrim Mac Dermott, (3) Arizona DOT, performed study areas. results also showed that Williams DOT’s formulas able estimate with error lower than 1%.