Arrangement for fairways in brackish water tidal zones to prevent or minimize deposits of silt and/or sand in a branch or enlargement of such fairways. The invention is realized by the installation of a flow wall system. At the entrance to the branch or expansion, a current deflection wall is submerged in the fairway at an upper level some distance from the bank so that a channel is formed near the entrance to the branch or enlargement to direct an flood tide into the branch or enlargement and a deflection sill is juxtaposed with the partition at a lower level to divert an incoming near-bed current of the fairway away from the entrance to the branch or enlargement. The cross sectional area of the channel is small when compared with the cross sectional area of the entrance to the branch or enlargement.