Lamellar settlers are used for stormwater treatment in order to separate suspended matter form water. In these settlers, the effective decantation area is increased thanks to the presence of many successive inclined plates.The problem of lamella settling tank is the inhomogeneous distribution of flow velocity between the inclined plates so this work focuses on the study of turbulent flow and its interaction with the successive plates.In this perspective, we propose a coupling of Euler and Lagrange approaches in order to model flow and sediment transport. The numerical model has been implemented in the Fortrancode. The finite volume scheme (ADI) was adopted as it ensures good precision with reasonable computation time. The model introduces the Lagrangian time constant CL to determine the size and lifetime of the eddies where the particles move.For testing our program we first studied the case of turbulent flow around a single plate and then two plates where we found satisfying results.Then we enlarged our study to study several plates. The obtained results show that the lamellar elements are efficient to reduce flow velocity and increase the sedimentation rate comparatively to conventional tanks with vertical obstacles or without barriers.