Comparison of Computed and Experimentally Assessed Times of Concentration for a V-Shaped Laboratory Watershed

Abstract

In comparison with a kinematic wave–based equation for estimation of the time of concentration, three methods, Ben-Zvi’s method, the modified Ben-Zvi method, and Izzard’s method, were applied to determine the time of concentration from the experimental hydrographs reaching an equilibrium flow state. The experiments were performed for stationary rainstorms on a V-shaped aluminum watershed in the watershed experimentation system (WES) at the University of Illinois in Urbana-Champaign, Illinois. The times of concentration determined by these three methods were compared to mathematical equations in the existing literature. It is found that the time corresponding to 89% of the maximum discharge as per the modified Ben-Zvi method yielded a generally agreeable time of concentration for the WES experimental hydrographs, while the criterion of 97% of the peak discharge as per Izzard’s method overestimates the time of concentration. It is found that Woolhiser and Liggett’s and Wong’s equations can predict the time of concentration acceptably well for the simplified laboratory watershed with overland slopes in the range of 0.5–5% and channel slopes in the range of 0.5–3%.