Author(s): M. J. Kim; K. S. Jun
Linked Author(s): Kyung Soo Jun
Keywords: Longitudinal dispersion; Numerical model; Nonconservative contaminants; Flushing effect; The nakdong river
Abstract: A numerical model is presented for the unsteady dispersion of nonconservative contaminants in natural streams. The model is based on a fractional-step finite difference method splitting the onedimensional longitudinal dispersion equation for nonconservative substance into a set of three equations for pure advection, first-order decay, and pure diffusion, respectively. At each time step, the equations are solved successively over a 1/3 time step by the two-point fourth-order Holly-Preissmann scheme, a local analytic solution, and Crank-Nicholson schemes, respectively. The model is tested using an analytic solution for the longitudinal dispersion of continuous source released into a nonuniform flow field. The model is applied to hindcast the phenol spill accident which occurred in Nakdong River, South Korea in 1991. Also simulated is the dispersion of contaminants presuming that the same accident might occur for the current stream condition which has changed significantly after the Four Major Rivers Restoration Project of Korea. Simulations were made to evaluate flushing effect of various gate operation strategies of weir gates for mitigating the pollution due to the accident.