Waccamaw River Basin EarthCache

Every surficial drainage system is unique and as different from the others as the variation between individual people. Similar to humans, the character and health of each drainage system is dependent upon its inheritance from the gene pool, its physical location relative to the geometry, lithology, and paleotopography of the underlying geologic units and the types, magnitudes, and patterns of energy flow through the ecosystem.

The focus of this earth cache is The Waccamaw River Basin in North and South Carolina. The headwaters of the Waccamaw River originate in North Carolina just north of Lake Waccamaw. It drains roughly 804,400 acres of Bladen, Columbus, and Brunswick Counties there before crossing over into Horry and Georgetown Counties in South Carolina. There it encompasses 5 watersheds and 765 square miles. The black waters of the Waccamaw River Basin incorporate the Lower Coastal Plains of the both states.

Almost half million acres, 36.9% is forested wetland (swamp), 26.5% is agricultural land, 19.2% is forested land, 10.5% is urban land, 2.8% is scrub/shrub land, 2.2% is non-forested wetland (marsh), 1.7% is water, and 0.2% is barren land. There are approximately 784 stream miles, 2,373 acres of lake waters, and 22,910 acres of estuarine areas in this watershed. The Waccamaw River flows across the South Carolina state line from North Carolina then joins the Great Pee Dee River as it forms Winyah Bay and drains into the Atlantic Ocean.

Extensive forest communities cover the Waccamaw floodplain, including cypress-gum swamp and bottomland hardwood forests. The bottomland hardwood forests of the Waccamaw are unique in the Carolinas in containing abundant Atlantic white cedar and live oaks, along with the more typical laurel and overcup oak and loblolly pine. These forest communities provide excellent habitat for wildlife such as bobcat, river otter, and neotropical migratory songbirds.

The Waccamaw drainage system (WDS) is situated on the outer coastal plain and on top of a major structural feature called the Carolina Platform. This structural high in the crystalline basement rocks separates the adjacent Southeast Georgia Embayment to the south and Salisbury Embayment to the north. The Carolina Platform is interpreted to be an Early Mesozoic rift, a tectonic block left behind during the continental breakup of North America and Africa as rifting began about 225-200 million years ago. The Carolina Platform is responsible for creating the major seaward protrusion along the mid-Atlantic continental margin that forms a unique coastal system.

Extensive seismic studies on the modern continental shelf suggest the Carolina Platform is a fairly stable structural feature with only minor instability through most of the Tertiary Period of geologic time. Researchers believe that the Carolina Platform is a topographically high erosional feature that formed an oceanic headland and controlled coastal deposition and development of the Carolina continental margin for the last 100 million years. The Carolina Platform is an structural block with an eroded paleo-topographic surface, geologists renamed the topographically highest portion as the mid-Carolina Platform High. Many researchers believe that the emerged coastal plain has been tectonically active initially up warping during the Cretaceous and continuing to rise sporadically through to the Holocene. The Waccamaw Basin formed in response to an episodic uplift of the river during the Pleistocene Era. Location of the river terraces along the northeast side of the river valley and the ongoing southwest movement of the river within its valley, suggests that uplift of the arch occurred throughout the Quaternary and continues into here at present.

Cretaceous Period stratigraphic units were deposited over the Carolina Platform and constitute an extensive sediment sequence that forms the geologic framework underlying the Waccamaw River Basin. Three Cretaceous stratigraphic units form the basement sequence of sediments that occur as seaward dipping units. Only the youngest Pee Dee Formation crops out and has a direct impact upon the modern dynamics within the WDS.

Throughout the Tertiary, shallow marine and coastal sediments were deposited around the headland of Cretaceous rocks occurring on the mid-Carolina Platform High. Most Tertiary units occur as a seaward thickening sedimentary wedge deposited off the northeast flank of the Cretaceous units. These Tertiary units crop out on the continental shelf as they wrap around the seaward nose of the structure. The Waccamaw River Basin is situated high and along the axis of the mid-Carolina Platform High with no Tertiary units of Paleocene through Miocene age occurring within the region. Thus, there was up to 60 million years of time when the Cretaceous sediments were severely weathered and eroded. Coastal marine sediments were repeatedly deposited during sea-level highstands and severely eroded during subsequent sea-level lowstands. The result is a highly dissected series of Pliocene and Quaternary coastal sediments perched on top of a severely eroded surface with significant paleo-topography and a paleo-drainage system cut into the Cretaceous sediments.

Incised areas occurred in what appears to be the modern Waccamaw River with its very broad floodplain. However, this valley fill does not all represent modern floodplain and can be further subdivided into the Pleistocene and Holocene period units. Most of the valley fill represents an antecedent floodplain that has slightly higher elevations and is dominated by paleo-channels and associated point bar scrolls. Wherever the modern Waccamaw River is incised down the channel is wide, deep, and fairly straight with broad sweeping meanders. These channels are usually rock bound along one or more sides and are very high so that they are not overtopped during normal flooding conditions.

Since the entire WDS is situated on the outer coastal plain, it is a black-water drainage system characterized by low hydraulic gradients and dominated by wetlands. All of these wetland habitats are characterized by high water tables and organic-rich soils overlying clay-based sediments. The WDS is "a showcase of biological richness" due to the diverse and extensive wetland habitats characterized by a wide variety of plant communities. Land and aquatic life flourishes in the basin.

Two different types of river segments make up the Waccamaw Drainage System. They are determined by the underlying geologic characteristics of the antecedent floodplain. Within the portions of the antecedent floodplain where the underlying Cretaceous Period Formation is topographically high, the channel is incised into the rock and forms the straight, wide, and deep rock-bound river segments. Within the portions of the antecedent floodplain where the Cretaceous Formation is topographically low, the modern channel is actively meandering and reworking the old floodplain sediments. This process has resulted in a narrow and shallow, highly sinuous channel that has developed an adjacent zone of low, modern floodplain which is incised into the higher antecedent floodplain. Wherever the modern river channel flows totally within its own active floodplain it constitutes Holocene Period or modern geologic period channel. About 50% of the river length is dominated by an actively meandering channel and associated active floodplain.

By the way, did you know that you live in a river basin? We all do! Everyone lives in a river basin. Even if we don't live near the water, we live on land that drains to a river or estuary or lake. Our actions on that land affect water quality and quantity far downstream. The topography of each basin determines the area that it drains, and whether that water - from creeks, rivers, springs, and aquifers - flows into the Atlantic Ocean or Gulf of Mexico.

A River basin is the portion of land drained by a river and its tributaries. It encompasses all of the land surface dissected and drained by many streams and creeks that flow downhill into one another, and eventually into one river. The final destination is an estuary or an ocean. As a bathtub catches all the water that falls within its sides, a river basin sends all the water falling on the surrounding land into a central river and out to the sea. The basin valley contains the primary channel occupied by the flowing water on a day to day basis. During specific storm events or during seasonal increases in rainfall, there is too much water for the primary channel to carry. The water flow now spills into a secondary channel, or floodplain. The type of riverine channel and associated floodplain is dictated by the type and load of sediment, frequency and intensity of storm events, geology urrounding the stream valley, and the latitude and elevation of the basin.

The geometry of a drainage basin is like an open-ended, elongated bowl tipped on its edge forming a concave upward slope. The headwaters of the basin consist of many small streams with steep gradients.

The waters in the Waccamaw River have been under consideration for reclassification as Outstanding Resource Water(ORW). This supplemental classification would designate these water bodies as "unique and special waters having exceptional water quality and being of exceptional state or national ecological or recreational significance". The designation would provide additional protection for the water quality in this system which is home to a large number of rare and endangered aquatic species and includes important associated bottomland forest ecosystems, which possess ualities of state and national significance. Existing threats to the health of the river include pollution from point sources, such as wastewater treatment plants, pollution from non-point sources, such as storm water runoff containing oil, fertilizers, pesticides and animal wastes and runoff of sediment due to soil erosion resulting from development.

The Waccamaw drainage system is situated between these two major urban areas that are rapidly sprawling towards each other. Groundwater discharge (base flow) represents a major input of water into the drainage system. There will also be an ever-increasing impact upon the river system through time. Fluvial geologists are studying the Waccamaw River Basin Sedimentation to define the problem of sediment pollution by relating it to geologic framework and changing land-use patterns, and to evaluate the long-term impact upon the drainage system as it relates to the geologic framework of the area. Sediment pollution is intimately tied to processes associated with different land uses and patterns of changing land use, which in turn is directly dependent upon the geologic framework of the WDS.

The South Carolina Department of Health and Environmental Control (SCDHEC) has implemented the Watershed Water Quality Management Strategy in order to more efficiently protect and improve the quality of South Carolina's surface water resources. This management strategy recognizes the interdependence of water quality and all the activities that occur in the associated drainage basin. One solution to these challenges is Low Impact Development. Low Impact Development (LID) is a comprehensive technology-based approach to managing urban storm water. It combines a hydrologically functional site design with pollution prevention measures to compensate for land development impacts on hydrology and water quality.

Water Quality tests on the Waccamaw have shown adequate oxygen levels for the variety of fish, alligator and other wildlife that call the Waccamaw River Basin home. However, tests have shown levels of toxins that exceed levels for human consumption. This has prompted warning signs to be posted where fishermen launch so that no one consumes too much of chemical levels that have been registered in fish tested along it’s watersheds.

At the Waccamaw River County Park and Launch you will visit, students of nearby Carolina University are routinely sample water to ensure the quality of the water for human consumption of fish and drinking water, recreation and general overall health quality for aquatic life. To log this cache, email us the answers to the questions below. Be sure to visit EZ Track's Traditional Cache also located here!

1. Estimate the width of the Waccamaw River from the coordinates provided at the end of the launch dock.

A. 30 feet b. 50 feet c. 70 feet

2. Shoot an elevation from the boat launch dock to see how far above sea level you are.

3.Name one of the many fish listed on the warning sign near the boat launch that is considered be contaminated. State what the contamination is.

4. Note what type of sediment is along the banks of the shoreline here.

Take a picture of your GPS with the Black Waters of the Waccamaw River and it’s sandy shores in the background.

“Waccamaw- the little lake, out of which the long and crooked river with its dark cypress waters flowed to the sea. The paper canoe shot into the whirling current which rushes out of the lake through a narrow aperture into a great and dismal swamp. Down the tortuous, black, rolling current went the paper canoe with a giant forest covering the great swamp and screening me from the light of day. Festoons of gray Spanish moss hung from the weird limbs of monster trees, giving a funeral aspect to the gloomy forest, while owls hooted as though it were night. The creamy, wax-like berries of the mistletoe gave a Druidical aspect to the woods. Such is the character of the Waccamaw, this most crooked of rivers.” Quote, Waccamaw River Society.