A versatile numerical model, the Virtual StreamLab, for carrying out high-resolution simulations of turbulent flows in natural streams is developed in this paper. The model is based on the curvilinear immersed boundary (CURVIB) method and features an efficient fractional step solver which is parallelized to enable highly-resolved simulations of real-life hydraulic engineering flows. The potential of the method is demonstrated by employing it to carry out large-eddy simulation of turbulent flow in the meandering stream currently installed in the St. Anthony falls Laboratory Outdoor StreamLab at University of Minnesota, MN, USA.