Resistance to flow due to an obstruction in the form of bridge piers give rise to many problems which are of engineering interests. An experimental study of the effects caused to some of these problems due the introduction of a vertical longitudinal slot to an obstruction in the form of a pier is carried out. Experiments are performed in the subcritical range of Froude number to measure the drag force and the energy loss with various slot width to pier thickness ratios, and the results are compared with those of conventional solid piers. The results obtained show a substantial reduction in the drag coefficient for slotted piers compared to the solid ones under the same flow conditions. Experiments also indicate the existence of an optimum value of slot width to pier thickness ratio. The loss in the total energy of the flow is also found to be smaller for the slotted pier compared to a similar solid pier.