Huang, M., Elshorbagy, A., Barbour, S. L., Zettl, J. D. and Si, B. C. 2011. System dynamics modeling of infiltration and drainage in layered coarse soil. Can. J. Soil Sci. 91: 185-197. A system dynamics (SD) model was developed to simulate transient infiltration and drainage processes in multilayered soils. STELLA Software was used as a stock-flow icon-based simulation environment. The developed SD model combined both physically based formulations and empirical assumptions to describe one-dimensional saturated-unsaturated water flow in the vadose zone. The model was successfully calibrated and validated using measured water contents during the infiltration and drainage phases, respectively, of a double-ring infiltration test. The simulation results were also compared with a finite element model of saturated/unsaturated flow (HYDRUS). The results showed that the SD model was capable of accurately simulating the various hydrological processes in multilayered soils, and could be a useful tool for designing reclamation covers. The simulated and measured results show that the presence of a finer sand layer overlying a coarse sand layer will increase the soil water storage at field capacity.