We propose an integrated electromagnetic-hydrodynamic inverse modeling approach for identifying field-scale unsaturated soil hydraulic properties and electric profiles from off-ground time-lapse ground-penetrating radar data. Hydrodynamic modeling based on the one-dimensional Richards' equation with homogeneous soil hydraulic parameters is used to physically constrain the full-wave radar electromagnetic inverse problem in a closed loop. Significant effects can be observed of water dynamics on the time-lapse radar data and numerical studies demonstrate the uniqueness of the inverse solution. The results suggest that the method is promising for non-invasive characterization of the shallow subsurface and monitoring of its dynamics.