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City of Copperas Cove Stormwater Master Plan (Ph. I & II)

City of Copperas Cove Stormwater Master Plan (Ph. I & II)

Challenge
The City of Copperas Cove, experiencing high growth rates and a population boom, had been struggling with ways to maintain development while precluding it from further exacerbating its existing drainage infrastructure. Definitively, Copperas Cove sought to grasp the extent and severity of the floodplains and flood hazards located within the City’s incorporated limits. The City selected Walker Partners to provide a comprehensive action plan to address the existing flooding challenges while laying the road map for responsible future growth within the community. 

Solution
The first order of business was data collection. A broad spectrum of information was collected from many sources including the City’s planimetric maps, zoning maps, and land use maps; hydrologic soil group maps from the USDA; highway bridge “as-built” drawings from TxDOT; and current Flood Insurance Rate Maps (FIRM) from FEMA showing the existing floodplains. Walker Partners conducted field reconnaissance by performing a drainage structure inventory and field survey of the channels.

Following the acquisition of data, each of the identified streams within the City were analyzed hydrologically and hydraulically. Computer software from Autodesk and the U.S. Army Corps of Engineers (HEC-HMS and HEC-RAS) were used to model the floodplains. The hydrologic analysis leveraged the capabilities of HEC-HMS to calculate the runoff rates and perform the complex storm water routing within the large drainage basins for desired 10, 2, and 1 percent recurrence intervals, more commonly known as 10-year, 50-year, and 100-year events. As a compliment to HEC-HMS, HEC-RAS was used for its ability to generate flood water surface elevations. The data generated from HEC-HMS, in conjunction with the field surveyed data, were used to construct the outline of the model for each stream within Copperas Cove. The flood water surface profiles for the 10-year, 50-year, and 100-year storm events were determined.

After the modeling was completed, the data was thoroughly vetted and floodplain maps were drawn to illustrate the hazard locations. A list of conceptual Capital Improvement Projects (CIP) were identified and prioritized in order to reduce flooding and promote economic development.

Two deliverables were delivered as part of Copperas Cove’s Drainage Master Plan. The first was updating their Drainage Criteria Manual (DCM) and the second was preparing and submitting their Phase II Storm Water Permit. The goal of preparing the DCM was to utilize existing, current, and industry standards in a format that would be straightforward and easy to follow. A team approach was used to ensure the updated DCM and Phase II Storm Water Permit met the requirements and goals of the City.

Ultimately, the Drainage Master Plan and all of its components were adopted by the City Council and are current policy. 

Value
The Drainage Master Plan and Drainage Criteria Manual adopted by the City has given Copperas Cove a clear vision of both the current drainage-related needs of the City and future needs that can be systematically addressed during development. The long-term plan will enhance the quality of life, sustain property values, and effect quality economic development in the community for years to come.