After the August 13, 2016 storm event, storm water overflow from Webb Coulee, a tributary to the Vermilion River, was trapped in a large portion of the Derby Heights Subdivision for weeks following the event. The subdivision retained 2 feet of standing water that was unable to drain causing significant damage and inability to access properties for an extended duration. Lafayette Consolidated Government (LCG) obtained Community Development Block Grant (CDBG) funding to implement drainage improvements to improve storm water flow within and out of Derby Heights and surrounding low to moderate-income neighborhoods.
LCG selected DDG to conduct a modeling study to identify the root cause of flooding in the area, develop an alternative to reduce both the severity and duration of the flooding compared with the August, 2016 event, and design and implement the proposed solution. Solutions under consideration entail additional culverts under Carmel Drive, improved conveyance of the D-Man Outfall, and constructing a hydrologic barrier to limit flow from Webb Coulee.
DDG developed a new HEC-HMS and 1D/2D RAS model for the D-Man Outfall. This model was combined with a previously developed RAS model for the Webb Coulee to understand the transfer of water from the Webb Coulee to the D Man Outfall during extreme events. An existing RAS model for the Vermilion River was used to determine the new model’s downstream boundary condition.