This article is devoted to the canonical problem of the radio-wave propagation in the presence of multiple knife-edges. The system of integral equations in a spectral domain for the scattered field is derived. On the basis of its solution diffraction and reflection effects spawned by the multiple knife-edges may be accurately modeled. The electromagnetic field is generated by a source of the monochromatic radio waves with an arbitrary beam pattern. The efficient numerical solution to the proposed equation is given. The comparison with the two-way parabolic equation (PE) method, the uniform theory of diffraction (UTD) method, and the finite element method (FEM) is presented.