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Church Creek Drainage Basin

Background

The Church Creek drainage basin drains a total of area of nearly 5,000 acres located along the western side of the Ashley River. Historically the area was composed mainly of old phosphate mines and marsh areas and today is approximately 80% developed with mainly residential and some commercial development. The present city limits consist of the residential neighborhoods of Shadowmoss, Hickory Hill, Hickory Farms, Grand Oaks, Village Green, Forest Lakes, and Canterbury Woods. The Church Creek drainage facilities consist of a natural drainage channel and marsh area located between the outlet 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.


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 know 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 4x8 ft. box culverts which created a second outfall to Church Creek.

In 2010 the city constructed a 4x12 box culvert to add additional capacity from the Bridge Pointe pond to the main channel. 

So far the city has spent $3,671,476 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.

Documents and Maps

Original 2001 Church Creek Drainage Basin Master Plan
Stormwater Master Plan Summary Report, Volume 1, December 2001
Stormwater Master Plan Technical Report, Volume 2, December 2001 Pt 1
Stormwater Master Plan Technical Report, Volume 2, December 2001 Pt 2
Stormwater Master Plan Technical Report, Volume 2, December 2001 Pt 3
ICPR Links & Nodes Map
Design Storm Floodplains - Map 1
Design Storm Floodplains - Map 2
Design Storm Floodplains - Map 3
Design Storm Floodplains - Map 4
Detention Summary Report and Figures

Volume 1 Sections
Church Creek Summary Report
Table 4 Existing Areas

Volume 2 Sections
Table of Contents
Technical Report
Section 8 ICPR Model Results

Volume 2 Appendices
Appendix B - ICPR Input File
Appendix C - House Elevations
Appendix C - Regressions
Appendix C - Charleston Airport Rainfall
Appendix C - Tide Means

2015 Updated Data
Church Creek Report Full 9-1-15
Link Node Map 9-1-15
Node Output 2-24-16
Cross Section Input
Drop Structures
Input Basins
Input Bridge
Input Channels
Input Nodes
Input Operating Table
Input Weirs
Subbasin Map

Additional Documents
2015 Church Creek Storm Event Memo 1-4-16
Church Creek Watershed Map
Check Valve Memo 7-18-16 Revised
Logging Road Summary Memo
Weir Memo 7-18-16 Revised
2016 Church Creek Drainage Network and Easements