  Acoustic scattering from layered seafloors exhibits dependence on both the
mean geoacoustic layering, as well as the roughness properties of each layer.
Several theoretical treatments of this environment exist, including the small
roughness perturbation approximation, the Kirchhoff approximation, and three
different versions of the small slope approximation. All of these models give
different results for the scattering cross section and coherent reflection
coefficient, and there is currently no way to distinguish which model is the
most correct. In this work, an integral equation for scattering from a layered
seafloor with rough interfaces is presented, and compared with small roughness
perturbation method, and two of the small slope approximations. It is found
that the most recent small slope approximation by Jackson and Olson is the most
accurate when the root mean square (rms) roughness is large, and some models
are in close agreement with each other when the rms roughness is small.
