A Modeling Approach to Identify Drainage Solutions for Downtown Columbus, Georgia

Abstract

Downtown Columbus is bordered on the west and south by the Chattahoochee River and by Weracoba Creek on the east. In many areas, the existing combined sewer system lacks the capacity to drain the highly urbanized area. In addition, the adjacent Weracoba Creek currently overflows into the low lying downtown area, increasing the threat of flood hazards on the already inadequate system. In order to investigate the behavior of the existing combined sewer system and to evaluate proposed improvements to mitigate localized flooding and flooding induced by Weracoba Creek, a comprehensive XP-SWMM model of the downtown area and the adjacent Weracoba Creek was developed. The modeling approach began with extensive field work to develop as-built maps of the existing combined sewer system to determine drainage structure locations, elevations, pipe configurations and invert data. A total of seventy six drainage sub basins were delineated and input into the model in conjunction with one hundred and six existing pipes. In addition to the complex pipe system, the model incorporates seven combined sewer overflow structures along the Chattahoochee River and a portion of Weracoba Creek that flows through an existing half mile long box culvert adjacent to downtown Columbus. The XP-SWMM model was calibrated by comparing the locations identified to flood in the model with actual recorded flood events using the 2, 10 and 25 year frequency storms. Currently, the model is being used to evaluate improvements to the existing combined sewer system and improvements to Weracoba Creek to reduce flood hazards in the downtown area for the 25 year design storm. The model will enable the design team to develop a strategic long range stormwater master plan to control flood hazards for the City of Columbus.