Scattered wave fields due to topographic features can influence surface vibrations significantly. Alluvial valleys present a special form, as they are often characterized by a complex geometry and have a different material than the halfspace. In this contribution, the Biot theory is assumed to describe relative displacements between fluid and solid phase in a 2D porous continuum. Moreover, the Wave Based Method (WBM) is introduced and extended to simulate efficiently wave scattering in a water-saturated system. This numerical method uses weighted wave functions, which fulfil exactly the underlying differential equations for a boundary value problem. A coupling procedure between a poroelastic halfspace and a poroelastic alluvial valley is formulated in the frequency domain. WBM models are formulated, compared with an example from literature, and tested for different degrees of coupling between fluid and solid phase. A Fourier synthesis approach is applied to model an incident wave front with a Ricker wavelet.