Definitions and Classifications

Water Definitions

Algal Bloom Rapidly occurring growth and accumulation of algae in a waterway resulting from excess nutrients that can lead to low dissolved oxygen levels and fish kills. (Sources: fertilizers, grass clippings, pet waste)

Biological Integrity The ability of an ecosystem to support and maintain a balanced and indigenous community of organisms.

Best Management Practice (BMP) or Stormwater Control Measure (SCM) Action or landscape modification that reduces the amount of pollution and/or the quantity of stormwater flowing into waterways. BMPs are actions, like picking up pet waste, or on-the-ground practices, such as rain barrels and rain gardens.

Chlorophyll a Allows plants to photosynthesize and gives plants their green color. Waters that have high chlorophyll a levels are typically high in nutrients (phosphorus and nitrogen), which cause algae to grow or bloom. When algae die, it depletes oxygen from the water and can cause fish kills.

Dissolved Oxygen (DO) The amount of oxygen available in water. Fish and aquatic organisms require adequate levels of DO to survive.

Fecal Coliform Bacteria Bacteria present in the intestines and feces of warm-blooded animals. High counts of fecal coliform bacteria in a waterway indicate the presence of other disease-causing pathogens, which can cause sickness and disease in humans and animals. (Sources: pet waste, sewer overflows, septic system failure)

Hypoxia Low dissolved oxygen levels in a waterway, which can result in fish kills.

Nutrients Substances (e.g. nitrogen and phosphorus) needed by plants and animals for growth; however, excessive nutrients in a waterway can lead to harmful aquatic weed and algae growth, low DO levels, and fish kills. (Sources: fertilizers, yard waste, pet waste)

Pathogens Disease-causing organisms, such as bacteria and viruses. (Source: pet waste)

PAHs (Polycyclic Aromatic Hydrocarbons) Toxic byproducts of petroleum and fossil fuels, which can be harmful to humans and aquatic life and can persist in the environment for a long time. (Sources: auto exhaust, motor oil, parking lot sealcoats, roofing tars, coal power plants)

Sediment Particles of silt, clay, dirt, or sand, caused by land-disturbing activities or natural weathering that wash into waterways. Sediment can settle to the bottom or remain suspended in water. (Sources: construction sites with failing erosion control, eroding streambanks, exposed soil)

Tidal Creek A saltwater creek that is influenced by tides. Many tidal creeks have oyster reefs along their shorelines.

Turbidity A cloudy condition in water caused by suspended sediment.

Watershed An area of land that drains into a specific body of water, such as a creek, lake, or river.

Water Classifications

The N.C. Division of Water Resources applies classifications to waterways, which define the best uses to be protected within those waters (e.g. swimming, fishing, drinking water supply, aquatic life). These classifications have an associated set of water quality standards to protect their designated uses. These standards may be designed to protect water quality, fish and wildlife, the free flowing nature of a stream, or other special characteristics. In addition, there may be a supplemental classification applied to protect several different uses or special characteristics within the same waterbody. Listed below are the freshwater and saltwater classifications that apply to Wilmington’s waterways

Freshwater Classifications

Class C Waters protected for secondary recreation (fishing, boating, and other activities involving minimal and infrequent skin contact), wildlife, agriculture, biological integrity, and fish/aquatic life propagation and survival.

Supplemental Classification
Swamp Waters (Sw) Waters that naturally have low flow and other characteristics which differ from creeks that drain land with steeper topography.

Saltwater Classifications

Class SC Saltwaters protected for secondary recreation (fishing, boating, and other activities involving minimal skin contact), fish and noncommercial shellfish consumption, fish/aquatic life propagation and survival, and wildlife.

Class SB Saltwaters used for primary recreation, such as swimming, and all Class SC uses.

Class SA Saltwaters used for commercial shellfishing and all Class SC/SB uses. SA waters are also High Quality Waters (HQW) by supplemental classification.

Supplemental Classifications
High Quality Waters (HQW) Waters rated excellent based on biological, physical, and chemical characteristics and having primary or functional nursery areas.

Outstanding Resource Waters (ORW) Unique and special waters having excellent water quality and being of exceptional state or national ecological
or recreational significance.

State Status/Reason

Indicates whether or not a creek is supporting its state classification/use and the reason why.

NC 303(d) List of Impaired Waters

Section 303(d) of the Clean Water Act requires states to develop and frequently update a list of waters that do not meet water quality standards or have impaired uses.

View NC's 303(d) list here.

Unfortunately, several of Wilmington’s waterways are on the 303(d) list because of pollution, such as fecal coliform bacteria and nutrients, which is washed from the land by stormwater runoff.