Abstract Understanding how heterogeneous sedimentary deposits affect fluid flow and contaminant transport has been greatly improved through outcrop studies. Such studies have aided in hydrogeological site characterization by identifying sedimentary structures that greatly impact flow and transport. The use of geophysical methods for delineating structures relevant to flow and transport such as fast paths, which control the initial breakthrough of contaminants, or sand-rich regions, which retard reactive contaminants, is beginning to receive much attention. In particular, ground-penetrating radar (GPR) was recently evaluated for this purpose within the framework of an aquifer analog study. Using models derived from digitized outcrop images, GPR simulations showed that field data were largely affected by non-uniform water saturation in addition to sediment heterogeneity. In the present work, we begin to explore the possibility of using GPR during transient flow to further aid in hydrogeological site characterization. A case study is presented in which a digitized outcrop image is chosen for the simultaneous simulation of variably saturated flow and GPR (for crosshole and surface reflection configurations). The sensitivity of the fluid distribution and of the GPR response to model parameters is investigated for the outcrop model during steady state and induced transient flow (ponding infiltration). In some cases, synthetic time-lapsed measurements are shown to offer information pertinent to hydrogeological site characterization.