In order to investigate the development process of the flow field and bottom boundary layer under breaking wave, a series of dam break experiment was carried out to simulate the propagation of a bore over coastal area. Particle image velocimetry (PIV) method was applied to obtain 2D flow field in vertical and streamwise direction. Following the sudden movement of upstream gate, a breaking bore is generated and propagation of bore was done on four different initial water depth conditions, each with five repeats to investigate different flow motion and process of boundary layer development under the bores. The repeatability of the generated waveform is good, however, turbulent structure of breaking bore, especially on the surface is complex and as a result, difference in velocity measurement is unavoidable. From the resulted velocity profile, is seen that breaking bore in a dey bed undergoes one uniform flow regime. The high momentum and turbulence are transported in whole water column overtime, alongside with the development of a bottom boundary layer.