Frequently, flow measuring flumes placed in unlined channels settle at the flume exit because of the scouring action of the high velocity flow leaving the flume. Usually, this settlement condition goes uncorrected in the field. A more satisfactory solution to the problem would be in evaluating the effect of this settlement upon the discharge rating of the flume. Four cutthroat flumes were selected for hydraulic testing in the laboratory. These flumes had been previously rated with the flume floor horizontal. In this study, hydraulic data were collected under both free flow and submerged flow conditions for each flume at various degrees of flume floor slope. The experimental results show that there is a very definite effect upon the discharge rating of a flume due to settlement. The amount of correction increases as the tilt angle increases. Also, the amount of correction increases as the flume length is increased.