RAPID: Patterns of Fluvial Sedimentation and Geomorphic Change Following an Extreme Flood Event

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NATIONAL SCIENCE FOUNDATIONGEOGRAPHY SPATIAL SCIENCES (GSS) PROGRAMABSTRACT1615154Allan JamesJohn KupferUniversity of South CarolinaThis rapid-response research project will delineate and quantify the effects of large floods that occurred in early October 2015 on numerous rivers and streams in South Carolina. Extreme flooding generates considerable erosion and sedimentation and provides an excellent opportunity to study how a severe flood can modify channels and floodplains. The ephemeral data collected soon after the flooding ended will improve basic understanding of sediment transport and deposition dynamics during these large, rare floods as well as their importance in the sedimentary record. In particular, the duration of stream power above a threshold value will help predict where and how much bank and floodplain erosion will occur and when the rates of change in stream power will coincide with patterns of sedimentation. Project findings will enhance basic understanding of the magnitude and nature of geomorphic adjustments to large floods. They will help guide policy makers at city, county, state and federal levels and at local watershed associations, and they will enable research scientists to develop more effective watershed management plans for urban streams. The project also will guide the development of graduate and undergraduate students from underrepresented groups in science and engineering and will build STEM capacity by incorporating undergraduate and graduate students into the research process through their involvement in field-based data collection and analytical procedures.The researchers will investigate the use of longitudinal variations in unit stream power and stream gradient index (SGI) as potential indicators for reach-scale changes in sediment flux that identify sites that are vulnerable to future flooding. Using state-of-the-art mapping techniques including global positioning systems (GPS), unmanned aerial vehicles (UAVs), and light detection and ranging (LiDAR), the investigators will map and measure channel adjustments to test theories, explain patterns, and develop predictive models of river erosion and sedimentation. While modern mapping technologies will help identify, locate, and recognize patterns of channel and floodplain change, UAVs will acquire low-altitude aerial imagery, which will be used with "structure-from-motion" (SfM) photogrammetric techniques to develop high-resolution, large-scale maps of selected sites. Spatial patterns of erosion and sedimentation measured by these methods will be compared with patterns predicted by analysis of stream power to test theories based on the duration of critical power and spatial changes in stream power. Improvement in the ability to predict channel erosion and deposition and subsequent changes in flood stages has enormous socioeconomic implications that will help guide future flood-mitigation efforts.