Church Creek Drainage Basin

Background

The Church Creek drainage basin today drains a total of area of over 10,000 acres located along the western side of the Ashley River. This area has been studied for over 20 years, and its flat terrain made it difficult to estimate the extent until the advent of modern high-resolution topographic information. We can now appreciate that historically, the area of watershed was much smaller. Early ditches, road construction, and stormwater management have redirected water towards Church Creek and away from other flow paths, enlarging the drainage area. 

The area that flows into Church Creek today was once composed mainly of marsh and lowland hardwood forests that were ditched and converted to rice fields and phosphate mines. Today the lower sections of the basin  are largely developed. The residential neighborhoods of Shadowmoss, Hickory Hill, Hickory Farms, Grand Oaks, Village Green, Forest Lakes, and Canterbury Woods fall within the Church Creek watershed. Church Creek passes through these neighborhoods in straightened ditches and flows down to marsh and then into the Ashley River under U.S. Highway 61 and the Seaboard Systems Railroad. Upstream of the Seaboard Systems Railroad, portions of the existing channel have been improved between Bees Ferry Road and the railroad.

Timeline

Significant development of the Church Creek drainage basin began in the early to mid-1970s. In 1986 townhomes constructed on Two Loch Drive flooded during a rain event. In response to this flood, Charleston County, SCDOT, and the City of Charleston combined efforts to increase the capacity of the basin's main outfall beneath the CSX railroad, adding three 72-inch culverts to the existing 66-inch culvert.

  • In the 1990s, new homes were constructed in the Still Shadow section of Shadowmoss. Throughout the 1990s these new homes were flooded during several rain events. After determining that the accepted engineering standards applied to stormwater system design were not effective in this drainage basin, the city approved a nine-month building moratorium and initiated a detailed study of the drainage basin.
  • In 2001 the city, through its consultant, developed an ICPR model of the basin which was calibrated through comparison of known flood events. The study resulted in new design standards for new development in the basin and recommendations for system improvements that could lower flood levels.
  • In 2005, capacity was added to provide additional stormwater storage in conjunction with construction of the Middleboro section of Shadowmoss.
  • In 2007, the city completed a diversion project that intercepted a significant portion of stormwater runoff from the eastern side of Shadowmoss Plantation. The new system included a new canal and dual 4 by 8 feet box culverts which created a second outfall to Church Creek.
  • In 2010, the city constructed a 4 by 12 box culvert to add additional capacity from the Bridge Pointe pond to the main channel.
  • In 2017, after several flooding events in succession, the city began coordinating with FEMA to buy the Bridge Pointe Town Homes site and convert it to open space.   
  • In 2019, the Dutch Dialogues focused on Church Creek in the final report (HYPERLINK: https://www.charleston-sc.gov/DocumentCenter/View/25055/Dutch-Dialogues-Charleston_Final-Report-September-2019) and the City led a grant application to the National Fish and Wildlife Foundation’s (NFWF) Emergency Coastal Resilience Fund for Habitat Restoration and Flood Protection. The grant was successfully submitted with community partners such as the Nature Conservancy and Clemson Extension.
  • In 2020, the city released new stormwater regulations for the basin to minimize the flood risk associated with development. They include comprehensive site planning and the integration of low impact design approaches that decentralize stormwater management. 
  • In late 2020, the city hired a consultant team to undertake wetland design on select properties owned by the city or collaborative partners in accordance with the NFWF grant. 

Updates

Given the history of augmentation and alteration in the watershed, no single action or installation of a nature-based practice will resolve the flooding. Instead, a holistic, basin-wide suite of practices will be required. These include adherence to the new stormwater regulations for new development, increased water storage in the mid and upper sections of the watershed, flood-prevention improvements to stormwater pond management, and homeowner retrofits to increase water infiltration. The city is actively pursuing each of these solutions.

So far the city has spent $4,196,476 to construct improvements and monitor the effect of stormwater runoff from new development so that it does not adversely affect existing development. Determined to continue to alleviate the drainage challenges in this basin, the City of Charleston is continuing to update the existing ICPR model, review proposed development designs to ensure adherence to the strict stormwater design standards for the basin, maintain the existing collection and conveyance system, and seek out additional capital improvement projects to improve drainage. 

As of the summer of 2021, the city has completed preliminary engineering and design on three sites that offer opportunities to reduce flood risk: the Bridge Pointe Town Homes, city-owned property near Wolk Drive and Mowler Court, and Crosstowne Church. 

Community Meetings


Bridge Pointe Town Homes Site Meeting

Meeting with design team to review and discuss the proposed concept plans with project engineers.

Thursday July 29, 2021 
7:00 PM – 8:30 PM
21 Dunvegan Drive, Charleston, SC 29412

 

Donuts with Designers: Wolk Drive and Mowler Court

An informal discussion over coffee and donuts to share proposed concept plans for the city-owned properties along Wolk Drive. 

Saturday July 31, 2021 
8:30 AM – 10:00 AM
63 Wolk Drive, Charleston, SC 29412

Documents & Maps

Original 2001 Church Creek Drainage Basin Master Plan

Volume 1 Sections

Volume 2 Sections

Volume 2 Appendices

2015 Updated Data

Additional Documents