In this work we propose a continuous system of differential equations to model the coupled dynamics of fluid and sediment under non-equilibrium saltation processes. The model is based on the equations of motion for fluid flow interacting with evolving landforms, combined with conservation laws for sediment flow integrated over the saltation layer. While drag force and grain-borne stress are calculated following the approachin Ref. [1], we reformulate the mass and momentum conservation laws without imposing restrictions on erosion rates or sediment velocities. This allows for a more accurate representation of sudden changes in fluid-sediment interactions over complex bedforms. A key aspect of our approach is the inclusion of a conservation law to track the evolution of the solid-fluid interface, which introduces additional forcing terms into the fluid momentum equations through dynamic modifications of the domain. A pivotal element of this study is the numerical solution of the coupled fluid-sediment equations of motion. We achieve this using a finite element method (FEM) designed for fluid flow over erodible beds and over non-removable materials [2]. A major innovation is the coupling of depth-integrated solutions for the sediment conservation laws within the saltation layer. The FEM formulation is implemented as a conservative, sign-preserving algorithm, commonly referred to as a non-oscillatory finite element method. This approach ensures accurate resolution of multiple evolving fronts and layers in the fluid-sediment flow by minimizing spurious residuals at interfaces during computation [3]. ACKNOWLEDGMENTS The research was supported by the Grant \#PID2020-115778GB-I00 funded by MCIN/AEI/10.13039/501100011033 References [1] G. Sauermann, K. Kroy, and H. Herrmann. Continuum saltation model for sand dunes. Phys. Rev. E, 64:031305, 2001. [2] J. Molina, P. Ortiz, and R. Bravo. A finite element method for partially erodible bed evolution coupled with multiphase flows. Comput. Methods in Appl. Mech. Eng., 405, 115853, 2023. [3] J. Molina, P. Ortiz, and R. Bravo. Fluid-evolving landform interaction by a surface-tracking method. Comput. Mech., 74, 993–1008, 2024.