A one-dimensional step-backwater model was used to simulate flooding conditions for Catoma Creek near Montgomery, Alabama. A peak flow of 50,000 cubic feet per second was computed by the U.S. Geological Survey for the March 1990 flood at the Norman Bridge Road gaging station. Using this estimated peak flow, flood-plain surveys with associated roughness coefficients, and surveyed high-water marks for the March 1990 flood, a flow model was calibrated to closely match the known event. The calibrated model then was used to simulate flooding for the 10-, 50-, 100-, and 500-year recurrence-interval floods. The 100-year flood stage for the Alabama River also was computed in the vicinity of the Catoma Creek confluence using observed high-water profiles from the 1979 and 1990 floods and gaging-station data.
The results indicate that the 100-year flood profile for Catoma Creek within the 15-mile study reach is about 2.5 feet higher, on average, than the profile published by the Federal Emergency Management Agency. The maximum and minimum differences are 6.0 feet and 0.8 foot, respectively. All water-surface elevations computed for the 100-year flood are higher than those published by the Federal Emergency Management Agency. The 100-year flood stage computed for the Alabama River in the vicinity of the Catoma Creek confluence was about 4.5 feet lower than the elevation published by the Federal Emergency Management Agency. The results of this study provide the community with flood-profile information that can be used for flood-plain mitigation, future development, and safety plans for the city.
