EFFECTS OF DIFFUSIVE WAVE AND FLOOD INUNDATION ON TIME OF CONCENTRATION

摘要

Time of concentration Tc is defined as the wave travel time from the most hydraulically remote point to the point of study. Tc is an important element in hydrological studies, especially in drainage system designs and the estimations of flood arrival time. The common approach in the estimation of Tc is based on Kinematic Wave (KW) approximation for both overland flow and river routing. This approximation, however, may not be appropriate on a flood plain with inundations. The main objective of this study is to propose the estimation of Tc with Diffusive Wave (DW) approximation considering the effect of flood inundation. The proposed method is demonstrated in the Kelantan River basin, Malaysia, focusing on a severe flood event in December 2014. This study compares the estimated Tc with other estimations based a Rainfall-Runoff-Inundation simulation and with a simple correlation method between rainfall amount in different durations and peak river discharges. In consequence, the proposed method with DW approximation with flood inundation showed closer estimations of Tc by the other two methods.