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.