In this study, the effects of land subsidence on water-surface elevation and depth profiles during flood conditions were investigated for a large, hypothetical, slope-controlled stream. Subsidence depressions, with a range of vertical magnitudes and areas were imposed on a hypothetical stream reach. Step-backwater computations were made to determine water-surface and depth profiles for a large hypothetical flood. Changes in the water-surface and depth profiles were related to the assumed subsidence to determine relative effects on flood profiles. The results may be useful in understanding and evaluating flood hazards where subsidence coincides with the flood plain of a large, upland stream.