In active remote sensing of low-loss and scattering-dominant areas, the effect of volume scattering can be modelled as a half-space random medium with lateral and vertical fluctuations. Correlation functions are assumed to be gaussian laterally and exponential vertically. The radiative transfer theory is developed in this paper to calculate backscattering cross sections. An iteration process is used. When calculated to first order in albedo, the result gives the single-scattering effects and confirms previous work. Calculated to second order, we find that the backscattered power exhibits depolarization effects. This important consequence is studied numerically by illustrating the backscattering cross sections as a function of incidence angles and frequencies.