This earthcache will bring you to a small, historic, stone bridge allowing Swamp Rabbit Trail to cross a minor tributary of the Reedy River.
The Reedy River, a tributary of the Saluda River, is about 65 miles long and spans across Greenville and Laurens counties in northwestern South Carolina. It begins in Travelers Rest, SC at the foothills of the Blue Ridge Mountains and flows generally south-southeastwardly through Greenville, Lake Conestee Nature Park, and the Piedmont region into Laurens County. It joins Lake Greenwood in Laurens County, which is formed by a dam on the Saluda River. Bedrock in this region is dominated by biotite-quartz-feldspar gneiss with interlayered sillimanite-mica schist and amphibolite.
Geomorphology is the study of the form or shape of the landscape, and how it changes through time. In the case of rivers, the focus is on the shape of the river channel and its floodplain. Changes to a river happen both naturally and as a result of human actions. For example, during extreme flood events, river channels often get wider and/or deeper, and may change their course completely.
All of these features of the river are shaped and influenced by the interaction of flow (highs and lows), sediment, and riparian vegetation. Erosion naturally happens at the outside of river bends where water is moving quickly. At the inside of stream bends, where water is moving slowly, sediment builds up. The result is a stream channel that is always slowly migrating in the direction of the outside of the bend. As the channel migrates, it leaves behind old channels, which can become side channels with slower-moving water. Side channels can also form around or behind mid-channel bars and islands that might form where sediment naturally deposits, or during large flood events where new channels are carved out of the floodplain. Riparian vegetation often serves to slow down channel migration, anchor sediment on bars and islands, narrow the channel, and create complex habitat conditions. When a river is flowing normally, it slows down in its backwater stretch and drops sediment onto the riverbed. However, when floods occur, the larger volume of faster-moving water can erode the riverbed.
While erosion will happen naturally, certain factors can speed up the process and cause problems. One of the most common issues is a lack of a soil-stabilizing root system. Grass or sparse vegetation doesn’t have the same effect as larger plants. Without a tree or shrub root system to hold soil in place, both surface water and the current can work together to erode the bank. In contrast, structures installed within a stream channel can actually accelerate stream bank erosion. Whether its large rocks or rubble, a bridge or culvert, or other kinds of structures, anything that restricts the water flow can increase water velocity and may create problems for downstream properties. Some signs of serious erosion problems include: a large area of bare soil on a steep shoreline bank, leaning or downed trees with exposed roots on the shoreline, unusually muddy streams during periods of high water or following a rainstorm, or wide, shallow areas in a stream.
To log this earthcache, please include a picture of yourself or a personal item in front of the stone bridge and send me the answers to the following questions:
1. Compare the current stream conditions to this historic photo of the stone bridge when it was first built. How has the shoreline at this location changed over the last century?
2. Describe how the stream flow, sediment, and vegetation has contributed to these changes or lack of change.
Cox Collection. Greenville County Historical Society. https://greenvillehistory.org/photogallery/coxe-collection-1/
Geomorphology. Four Corners Water. https://www.fourcornerswater.org/dolores-river/geomorphology#:~:text=Changes%20to%20a%20river%20happen,may%20change% 20their%20course%20completely.
Greenville. Perry-Castañeda Library Map Collection. https://maps.lib.utexas.edu/maps/topo/south_carolina/txu-pclmaps-topo-sc-greenville-1935.jpg
Greenville, South Carolina. Pickatrail. https://www.pickatrail.com/topo-map/g/7.5x7.5/greenville-sc.html
Rivers can suddenly change course, study says. Earthsky. https://earthsky.org/earth/rivers-suddenly-change-course-satellites/
Measom, K. Geomorphology of the Reedy River in the Vacinity of Lake Conestee Nature Park, Greenville County, South Carolina. The Geological Society of America. https://gsa.confex.com/gsa/2015SE/webprogram/Paper253581.html#:~:text=Historic% 20topographic%20maps%20and%20land%20records%20also,the%20region%20is%20 dominated%20by%20biotite%2Dquartz%2Dfeldspar%20gneiss
Shoreline Erosion: Causes, Prevention, and Control Options. Wisconsin Department of Natural Resources. https://dnr.wisconsin.gov/topic/Waterways/shoreline/info-erosion.html
Streambank Erosion. 2023, June 30. Snohomish Conservation District. https://snohomishcd.org/sound-nature-fact-sheets/2018/2/16/streambank-erosion
The Reedy River. Friends of the Reedy River. https://www.friendsofthereedyriver.org/the-reedy-river
What Causes River to Meander? Essential Wilderness. https://essentialwilderness.com/what-causes-river-to-meander/