This study investigates experimentally the flow structure between two identical square cylinders as well as in the wake of downstream cylinder that are in-line positioned in tandem. The experiments are performed in a large scale water channel under shallow water conditions. Time-averaged streamline pattern as well as vorticity and turbulence statistics were calculated using Particle Image Velocimetry (PIV) measurement method for different gap ratios (G/D = 0.5 to G/D = 5, where G is the distance between the cylinders and D is the diameter of cylinder) between the cylinders at a fixed Reynolds number of 4470. The measurements were conducted for both side view and plan view configurations at Froude number Fr = 0.186. The results obtained under shallow water conditions are compared with those obtained under deep water conditions by other researchers and it is found that, as explained in detail in the manuscript, the flow structures are remarkably different especially in the region between the two rectangular cylinders. (C) 2014 Elsevier Masson SAS. All rights reserved.