Authors: Joni Corbin*, The University of Alabama, Lisa Davis, The University of Alabama, Matthew Therrrell, The University of Alabama
Topics: Geomorphology, Water Resources and Hydrology
Keywords: paleofloods, dendrochronology, hydraulic modeling
Session Type: Paper
Presentation File: No File Uploaded
In this study, we use paleoflood hydrologic techniques to develop a chronology of flood events that pre-date stream gauge data for South Sauty Creek, a tributary of the Tennessee River in north Alabama. Paleoflood hydrology uses physical evidence of flooding to reconstruct the timing and magnitude of floods that occurred prior to historical and instrumental data. South Sauty’s gorge setting makes the stream highly prone to large floods, which as recently as 2019 resulted in loss of life. Streamflow data only begins in 2011, providing limited data for understanding the large floods generated by this stream. Tree core samples were collected from oak (Quercus) trees with flood impact scars in the riparian zone, and dated using standard dendrochronology techniques. The earliest dated flood in the cores occurred in 1758 C.E. Preliminary findings suggest that all of the tree scar heights correspond to stages associated with the 25-year event that occurred in 2015. Sediment entrainment equations based on the Shield’s parameter were used to determine the minimum water height necessary to move the 10 largest imbricated cobbles located in channel adjacent to the tree-sampling site. We use HEC-RAS 5.0.6 to determine the discharge and flow recurrence interval associated with the stage that transported the imbricated boulders. Transportation of 80% of the measured cobbles is associated with flows greater than the largest flows on record. Future work will expand the data set to include higher tree scars to isolate the dates of larger flood events based on inundation mapping of the floodplain.