Ecological Effects of Hydrological Process on Time of Concentration

Ecological theory emphasizes headwater streams and wetlands as hotspots for metabolism of terrestrially derived organic matter and biogeochemical transformations. Time of concentration T-c is defined as the wave travel time from the most hydraulically remote point to the point of study. T-c 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 T-c 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 T-c 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 T-c 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 T-c by the other two methods.