Richland County is located in the central portion of South Carolina. The total land area within the county limits is 748 square miles. According to U.S. Census Bureau figures, the population has increased from 233,868 in 1970 to 292,601 in 1996.

The past history of flooding on the streams in Richland County indicates that flooding may occur during any season of the year. However, floods on the larger streams, the Broad, Congaree, and Wateree Rivers, are most likely to occur from June through October as a result of tropical hurricanes.

Flood records for the Congaree River, Broad River, and Gills Creek were available in the USGS Water Supply Paper 1673. The three worst floods on the Congaree and Broad Rivers occurred in August 1908, August 1928 and October 1929. Peak discharges for these events at the Congaree River gage below Gervais Street at Columbia were 364,000 cubic feet per second (cfs), 311,000 cfs and 303,000 cfs, respectively.

The maximum stage recorded on the Congaree River at the Gervais Street gage was 152.8 feet, National Geodetic Vertical Datum of 1929 (NGVD). The 100-year flood under existing conditions would reach an elevation of 155.8 feet NGVD at the gage.

Principal flood problems along Reeder Point Branch and Mill Creek are generally on the upstream side of railroad embankments for the CSX Transportation and Southern Railway. Although there is little development in the floodplain at present, development that is under construction or planned for construction could be subject to fairly deep flooding.

The flood problems along Gills Creek are compounded by a number of large and small lakes formed by dams across Gills Creek and two tributary streams, Jackson Creek and Little Creek. In the past some of these dams have failed and others have been purposely breached to prevent failure. Results indicate that Lake Katherine Dam, Forest Lake Dam and several other dams upstream from Forest Lake would fail during floods of 50-year frequency or greater. Dam failures in the upper basin would increase peak flood discharges at Forest Lake and Lake Katherine, but results indicate that both dams would fail during floods of 50-year frequency or greater even if none of the upstream dams failed. Both the Forest Lake Dam and the Lake Katherine Dam failed during major floods in the 1940’s and were rebuilt or repaired under military supervision. At the time these events occurred, there was very little development in the downstream floodplain. A major flood under existing conditions would overtop Forest Lake Dam and Lake Katherine Dam. The high water velocities would erode the downstream faces of both dams, causing them to fail. The combined effect of deep flooding and high-water velocities would result in extensive damage to homes, commercial structures and other facilities between Forest Lake and Garners Ferry Road.

Along Bay Branch between Sunset Drive and the Columbia corporate limits, several residential structures are located dangerously close to the stream. During major floods, some of these structures will be subjected to deep flooding and high water velocities. Smith Branch, Eightmile Branch and the other streams studied in detail are capable of reaching developed property at various locations, and during major floods, they could cause significant damage.

Flood problems along Jackson Creek and Little Jackson Creek are located primarily along those portions, which are downstream of dams that would fail during major floods. Spring Lake Dam, Arcadia Lake Dam, Windsor Lake Dam, Pine Lake Dam, and Parliament Lake Dam are located on Jackson Creek and would fail during a major flood. Springwood Lake Dam in Little Jackson Creek could also be expected to fail during a major flood. Development immediately downstream from these dam ranges from intense commercial development downstream of Springwood Lake, to residential areas downstream of the other lakes.

Along Stop Creek, Smith Branch, and the three tributaries to Crane Creek are mostly undeveloped at this time. However, development in the area is expected and floodplain management information is needed to prevent unwise use of the floodplains.