The Roanoke and Cashie Rivers are brown water and black water systems.

Brown Water
Swift moving water found in rivers and creeks that have their source west of the Coastal Plain. Brown water originates as runoff and contains an abundance of suspended sediments such as clay, sand and loam particles. It is rich in minerals and other nutrients, having the appearance of cream colored coffee. The Roanoke is a brown water river.

Black Water
Water found in slow moving rivers and creeks that have their source (or beginning) on the Coastal Plain. Many originate in backswamps and all have characteristic natural tannic acid, a product of decaying organic vegetation, giving the water the look of clear English tea. Such water is high in acidity and organic matter but low in minerals and other nutrients. The Cashie River and Gardner's Creek are examples of black water systems.