As mentioned in my previous post “Overflowing,” Charlotte-Mecklenburg became the first community in the country to include current FEMA floodplains and future projections (called Community Floodplains) on official floodplain maps. Community Floodplains show where flooding is likely to occur in the future based on projections of development upstream. Floodplain development restrictions in Charlotte therefore apply to both FEMA Floodplains and Community Floodplains. Across Mecklenburg County, almost 20,000 acres of land is within regulated floodplains. Despite the Floodplain Buyout Program that was started in 1999, there are still 2,700 commercial and residential structures within the regulated floodplain. During large rain events, many of these structures are at risk (CMSWS).
In browsing Charlotte’s Interactive Floodplain Map, I noticed the section of Little Sugar Creek after Freedom Park seems to include large sections of developed property within the floodplain. This is primarily all residential area.
Alluvial Soils
According to the Mecklenburg County Soil Survey, Monacan soils are the prevalent map unit along Little Sugar Creek. Monacan soils formed in recent alluvial sediments of the Piedmont and Coastal Plain, and slopes are commonly less than 2 percent. Soils of the Monacan series are deep, moderately well and somewhat poorly drained with moderate permeability.
In upland areas around Little Sugar Creek, Cecil and Pacelot are the predominant soils series, especially around Freedom Park. Pacelot soils consist of very deep, well-drained, moderately permeable soils that formed in material weathered mostly from acid crystalline rocks of the Piedmont uplands.
The “Cecil” is the official state soil of North Carolina, as more than 1.6 million acres of the NC landscape is covered by Cecil soils. Cecil soil consists of very deep, well-drained, moderately permeable, residual soils in upland areas of the Piedmont. These soils typically can be found overlying igneous and metamorphic rocks. Cecil soils are usually 6-8 feet deep and unweathered or slightly weathered bedrock can be found underneath. Since Ceci soils are upland soils, typically occuring on broad to narrow ridges, they are considered to be well-drained. Iron oxides observed in Cecil soils contribute to their characteristic red color (Linda, 2012).
As a well-drained soil, the Cecil soil series is used for a variety of purposes from agriculture to urban uses since the water table is far from the surface. The USDA considers Cecil soils to be prime farm land. Dominated by kaolinite clay, ceci soil is not prone ot swell and shrink as much as other soils comminated by clay. This means that houses and roads built on cecil soils are not as likely to be impacted from shrinking or swelling. However, with high amounts of clay also comes decreased permeability and susceptibility to erosion. Permeability issues are most often seen with urban land uses (Lindbo, 2012).
As a residual soil, the Cecil Series developed directly from the bedrock beneath it. The complex geology of the Southeast Piedmont bedrock is the result of the erosion of ancient mountain chains over several hundred million years. The metapmorphic and igneous bedrock that Cecil Soil overlays is described as felsic, or containing high amounts of quartz, feldspar and mica. The weathering of these and other minerals results in soils high in kaolinite clay (Lindbo, 2012). Along Little Sugar Creek in Freedom Park, there are several locations where you can observe large outcroppings of the native bedrock material, as seen in the bottom right of the image below.
References:
Lindbo, D., Lieberman , J., & Anderson , D. (2012). Cecil North Carolina State Soil. Madison, WI; Soil Science Society of America.
USDA. (1999, July). Monacan Series. Official Series Description - MONACAN Series. https://soilseries.sc.egov.usda.gov/