2.1 Model descriptions
Based on the field investigation in the upper reach of the Inbuk Stream, Korea, we have developed a 2-Dimensional finite element flow model using FEFLOW 7.0 (Liu et al., 2009). In this study, we adopt and improved the model to simulate water exchanges across the stream-to-riparian continuum induced by flood waves. Two improvements have been made to the model. First, the free development of seepage was taken into account in the stream-aquifer interface of the model, that is, the original time-varying head condition (Dirichlet) was replaced by the mixed boundary condition that combines the Dirichlet condition with flow constraints, as shown in Fig. 1. Second, the improved model considered the poroelastic response of the aquifer media caused by the change of hydrostatic load and hence the corresponding governing equation was modified, similar to Reeves et al. (2000), Gardner and Wilson (2006) and Boutt (2010). Considering the above improvements, some input parameters of the model, including the maximum saturation (S s), effective porosity (n e) and specific storage (S 0), were re-calibrated (Table 1). TheS s was re-calibrated because the mixed boundary conditions of the model would avoid the infiltration of unsaturated boundary nodes and lead to the relative decrease in maximum saturation of the VG model involved in the Richards’ equation. Then e and S 0 were re-calibrated because of the compressibility of fluid and solid media as well as the poroelastic response. The input parameters of the improved model are shown in Table 1.