Thursday, March 20, 2008

Environment, geology, and wildlife


The Congaree River, 51 miles long from the confluence of the Saluda and Broad rivers at Gervais Street Bridge to the Wateree River, is a bottomland hardwood forest ecosystem. Bottomland hardwood forests are characterized by frequent flooding and by the deciduous trees that thrive in these wetlands. Bottomland hardwood support a diverse number of plant and animal species that rely on periodic flooding, abundance of natural cover, and foraging opportunities year round. They are commonly found in the floodplain of rivers in the Southeast and South Central U.S.

Two hundred years ago, old growth bottomland hardwood forests covered almost thirty million acres across the Southeast. Today, only a small percentage remains due in part to river impoundment, development, and the conversion of forest to farmland. Congaree National Park is home to one of the nation’s last significant tracts of old growth bottomland hardwood forest.


The fall line is a narrow zone of transition between the Piedmont and the Coastal Plain and is so named because it marks the last appearance of bedrock waterfalls in river channels along the Atlantic Coast. Upstream from this point, river channels are rocky and straight, with abundant rapids. Below the fall line, rivers tend to open up and bend gently back and forth as they flow over the coastal plain. From a geological perspective, it represents the contact between outcrops of crystalline Piedmont rocks (like granite) and the sedimentary deposits of the Coastal Plain.

The modern fall line crosses the Congaree River just south of the Gervais Street Bridge. If you watch closely you can see the character of the river, as well as the vegetation, begin to slowly change within a half-mile of the Gervais Street Bridge. The banks contain Coastal Plain vegetation starting just below the bridge, but there are outcrops of rock in the river channel down to just above the Cayce Landing. Historically the fall line marked the inland limit of major river travel, and is the reason for the location of Columbia, as well as several other major cities including Raleigh, NC, Richmond, VA, and Washington, DC.

The Congaree River Valley is a broad notch cut into the Upper Coastal Plain and filled with river deposits. These deposits are shaped into numerous terraces, which are flat surfaces representing old floodplains. Terraces are separated by fluvial scarps, which represent periods of significant erosion when the river cut deeper down into the earth. The younger terraces were deposited by rivers emptying into shorelines of the Middle and Lower Coastal Plains over the last 3 to 3.5 million years.

The Congaree River Floodplain contains many old river courses dating back at least 21,000 years, during the last ice age. From this colder time, we have pollen, which acts as a fingerprint for plants, from spruce trees. In order to find spruce trees growing at this elevation today, one needs to go as far north as Eastern Canada. Other deposits in the Congaree River Floodplain include an old river course that formed at a time when the river was not a single channel but a network of braided channels. This deposit, which formed under cold, ice age conditions, may be as old as 60,000 years. Other places in the Congaree River Floodplain contain sand dunes that were forming during the last ice age, likely as recently as 15,000 years ago.
Click here to learn more about South Carolina’s geology.


The Congaree River corridor is home to many mammal species. On a trip down the blue trail one is likely to encounter white tail deer, beaver, river otter, and the invasive feral hog. The federally endangered shortnose sturgeon is one of the many fish species that migrate from coastal waters to spawn in the Congaree River near Columbia. Other migrant species include striped bass, American shad, and blueback herring. Learn more about endangered and threatened species in South Carolina.

America’s national symbol, the bald eagle, often visits the Congaree River, especially near Columbia. The eagles fish for food among the river’s rocky shoals. Another stately bird, the swallowtail kite, is a rare sight in the lower river near Congaree National Park. Mississippi kites and red-shouldered hawks are fairly common sightings. Species you may see and are likely to hear include barred owl, pileated woodpecker, yellow-billed cuckoo, northern flicker, chimey swift, and belted kingfisher. Get a checklist of birds you may spot in Congaree National Park.

Fishing is a popular activity on the Congaree River. The upper section of the blue trail, through Columbia, supports a healthy population of smallmouth bass that have moved downstream from the Broad River in recent years. In the spring, large numbers of striped bass migrate up the Congaree River to spawn. Fish are typically in the 5-10 pound range with a few over 30 pounds caught every year. Largemouth bass are common throughout the river and provide good angling year round. Large blue catfish as well as flathead and channel catfish can be found in some of the deeper holes in the lower section of the trail. A South Carolina fishing license is required to fish on the Congaree River.

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