Primeval Floods

Mark Catesby was a naturalist who spent time in Virginia, South Carolina, and the Bahamas between 1712-1726 with the exception of 3 years when he returned to England.  His specialties were botany and ornithology, and his accounts of the natural history of the south bridges the gap between those of John Lawson who was murdered by Indians in 1711 and those of the Bartrams who explored the region in the mid-18th century.  When Catesby resided in South Carolina, there were still mixed herds of elk and bison as far south as the piedmont region.  By the time William Bartram traversed the region, all he saw of these animals were the bones of specimens that had been killed years before.  Catesby often accompanied Indians on their hunts for bison, bear, and cougar.  He saw the region long before the ecosystem had been tamed and, in my opinion, spoiled.  In Catesby’s time, Europeans had settled just a narrow 5 mile strip along the coast, and much of the interior was wilderness thinly occupied by a declining Creek Indian population.

Circa 1680, European traders established a small post 4 miles south of present day Augusta, Georgia, and they gave it the name Savannah Town, not to be confused with the city of Savannah built on the coast of Georgia by order of General Oglethorpe decades later.  (The frequent use of the word, savannah, suggests an abundance of open grassy environments in these locations.)  The site of Savannah Town was as far as boats could travel up the Savannah River year round.  Twenty miles upstream, rocky cataracts prevented boat travel all year long, but near Savannah Town, sandbars intermittently formed, impeding boats for months at a time.  Indians traded deer skins , a leading export here till the late 18th century, for goods such as knives and iron pots.  However, the Indians didn’t understand the European concept of credit, and the European traders beat and enslaved Indians who didn’t pay off their debts.  This was in the days of indentured servitude when poor white people faced the same kind of punishment.  The Creek Indians retaliated by burning Savannah Town to the ground in 1715.  In response to this attack, the following year, traders and soldiers built Fort Moore on a nearby bluff overlooking a loop of the Savannah River.  Residents of Fort Moore witnessed an incredible flood in 1722 when, as if God wanted to wash away the wickedness of the Creek Indian vs. British merchant conflict, all of  New Savannah Town was destroyed.  The below passage is Mark Catesby’s description of this awesome and untamed act of nature.

“When great rains fall on the mountains, these rapid torrents are very sudden and violent; an instance of which may give a general idea of them and their ill consequences.

In September 1722, at Fort Moore, a little fortress on the Savannah River, about midway between the sea and the mountains, the waters rose 29 feet in less than 40 hours.  This proceeded only from what rain fell on the mountains, they at the fort having had none in that space of time.

It came rushing down the river so suddenly, and with that impetuosity that it not only destroyed all their grain, but swept away and drowned the cattle belonging to the garrison.  Islands were formed, and others joined to the land.  And in some places the course of the river was turned.  A large and fertile tract of low land, lying on the south side of the river, opposite to the fort, which was a former settlement of the Savannah Indians, was covered with sand 3 feet in depth and made unfit for cultivation.  This sterile land was not carried from the higher grounds, but was washed from the steep banks of the river.  Panthers, bears, and deer were drowned and found lodged on the limbs of trees.  The smaller animals suffered also in this calamity; even reptiles and insects were dislodged from their holes, and violently hurried away, and mixing with harder substances were beat in pieces, and their fragments (after the waters fell) were seen in many places to cover the ground.”

Map showing the location of New Savannah.  It was founded over 50 years before the better known modern city of Savannah, Georgia on the coast.

Flood of 1908 on Broad Street in Augusta, Georgia.  The city built higher levees after this one.  A flood of 1990 even breeched this, but it would have been much worse, if not for the construction of Clark Hill Dam upstream. 

It’s astonishing to realize this area didn’t even receive any rain, the flood resulting from storms that occurred many miles to the north.  Just imagine the aftermath of this flood: rotting corpses in the trees above, crushed animal parts strewn all over the ground, new islands formed, loops of the river completely rerouted, and much of the Fort’s food supply washed away.  Wow, what an example of nature’s fury.  In the Augusta area alone similar devastating floods occurred in 1796, 1840, 1865, 1887, 1888, and 1908, and this is just in recorded history.  But over the past 150 years, engineers have built drainage ditches, levees, and dams alongside and across every major river in Georgia, greatly reducing the frequency and intensity of floods, so a “freshet” like the one of 1722 is not likely to occur again as long as man maintains civilization.  This may be a good development for humans, but it has altered the natural environment in a way that has been detrimental to many species.  Below is an enumeration of the types of environments created or heavily influenced by primeval floods.

1. Canebrakes.  Floods that left standing water for any length of time killed trees by depriving them of oxygen, and thus opened up the canopy.  Floods also deposited sediment and greatly enriched the soil.  The combination of open sunny conditions with fertile soil led to the occurrence of vast stands of bamboo cane extending for many miles.  It seems counterintuitive, but soils especially rich in nitrogen host a low diversity of species, and canebrakes were an example of a single species occupying tracts of hundreds of square miles.  The bamboo canes provided forage for bison, feral livestock, and swamp rabbits, and during the Pleistocene would have fed mammoths and horses.  Bears and big cats liked to den in these dense thickets. (See:https://markgelbart.wordpress.com/2013/01/28/canebrakes-are-forlorn-landscapes/)

2. Buffalo Meadows. Mark Catesby found meadows where the grass grew 6 feet high.  It would be hard to find grass growing this tall on modern worn out soils in the south.  Settlers took advantage of the rich soils covered by bamboo cane and tall grass, converting them to field crops.  The yield was worth the risk of a once in 20 year flood.  Both these environments disappeared rapidly upon the onset of European colonization.

3. Bottomaland Forest.  Most of the modern day floodplains abandoned or left undeveloped have grown back to bottomland forests of sweetgum, mesic-loving species of oaks, sycamores, and loblolly pines.  On virgin soils enriched by floods, those trees grew to enormous size, much larger than most presently growing.

4. Sand Covered Patches.  I haven’t found anything abut this type of environment in the literature, but Catesby’s account of the 1722 flood mentions a barren area of river deposited sand 3 feet thick.  I hypothesize these areas gradually developed soil on top of the sand where young stages of forest succession would grow.  Perhaps because of the low soil nutrients, these patches stayed in scrub and brier for prolonged periods of time and would have attracted rabbits, not unlike the original environment of Coney Island, New York.

5. Oxbow Lakes.  Floods created cut-off meanders–habitat for fish that preferred lake over river.  Modern day dams have eliminated spawning grounds for once abundant sturgeon and other species. 

An oxbow lake forms when a meander of the river gets cut-off.

Events similar to the flood of 1722 explain how some fossil deposits originated.  Drowned animals and downed trees rapidly became covered in sediment.  Floods also destroyed fossil deposits by washing sediment downstream.

Floods were much less common during Ice Ages because the climate became more arid.  Floods were more common during interstadials and interglacials.  The time periods between 15,000 BP-12,900 BP and again from 11,000 BP-6,000 BP were ages of superfloods in the south.  Geologists have discovered evidence of super meanders in river valleys and large sandbars known as scrolls that date to these time periods when storms were stronger than those of today, probably due to rapid deglaciation releasing so much precipitation into earth’s atmosphere.

References:

Elliott, David; and Roy Doyou

“Archaeology and Historical Geography of the Savannah River Floodplain near Augusta, Georgia”

University of Georgia Lab of Archaeology Series #22 1981

Feduccia, Alan

Catesby’s Birds of North America

University of North Carolina Press 1985

 

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