The unsteady bore wave diffraction patterns generated by a bore impinging on a circular cylinder and that generated by a bore passing through a contraction-expansion channel are simulated using high resolution nonoscillatory schemes. The two-dimensional shallow water equations in general curvilinear coordinates are used and the Strang-type dimensional splitting is employed. It was demonstrated that truly nonstationary hydraulic wave diffraction involving regular to Mach reflection, bore-bore collisions and their resulting complex interactions can be accurately computed by the present method.