Available data for floods in the vicinity of Montgomery since the late 1800 's indicate that the flood of 1886 is the highest since settlement of the area in 1814. Profiles for floods in 1948, 1961, 1976, and 1979 were defined using floodmarks and recorded peak stages at gaging stations at Selma and Montgomery. The floods in 1948 and 1961 occurred before construction of Robert F. Henry Lock and Dam (formerly Jones Bluff Lock and Dam and Millers Ferry Lock and Dam). Considerable water-surface differences are indicated between the profiles for periods before and after construction of the dams. The investigation included a step-backwater model to reproduce profiles based on the actual flood profiles. After the actual flood profiles were reproduced, the model was used to compute additional profiles showing the effects of varying tributary inflow. The profiles were computed for discharges ranging from 80,000 ft3/s to 500 ,000 ft3/s. Stage-discharge relations were then developed for five sites upstream from Selma. Discharge coefficient curves for prevalent types of flow over the spillway at Robert F. Henry Lock and Dam were developed using discharges obtained from current-meter measurements and standard discharge equations for flow through gate-controlled spillways. (USGS)
