Collaborative Research: Defining controls on incisional avulsions in alluvial basins

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Collaborative Research: Defining controls on incisional avulsions in alluvial basinsRiver avulsion occurs when water is diverted out of a river and creates a new channel on the surrounding floodplain. The associated flooding can be catastrophic for people living along rivers, but hazard mitigation is difficult because models cannot predict the timing, location, or style of river avulsion. Incisional avulsion occurs when a new river channel is established through erosion rather than deposition, and, although it is common in some river systems, this avulsion style is particularly poorly understood. The goal of this study is to define the sedimentologic and hydrodynamic conditions associated with incisional avulsions. Using combined modeling and field approaches the PIs will evaluate how characteristics such as floodplain topography, slope, ground cover, and overbank deposition control avulsion styles and test the hypothesis that incisional avulsions occur in steep fluvial systems with topographically rough, unvegetated, well-drained floodplains that lack abundant overbank suspended-sediment supply. Modeling work will be conducted with Delft3D, a physics-based numerical model that solves the equations for water flow and sediment transport, and field-data collection will focus on ancient strata where channel and floodplain characteristics can be measured for large numbers of paleoavulsion deposits.The results from this project will help improve prediction of avulsion flood hazards and will enhance understanding of the relationships between channel avulsion and floodplain erosion and deposition. Avulsion is also a primary control on the distribution of fluvial hydrocarbon, groundwater, and CO2-storage reservoirs. Better understanding of avulsion processes gained through this research will aid subsurface predictions of reservoir quality and location. Broader impacts of this work also include development of a self-paced, web-based education module about rivers and avulsions. In collaboration with the Geoscience Outreach Foundation the PIs will design a Rivers from Above curriculum comprising guided tours of rivers and avulsions using Google Earth and Google Maps. Rivers from Above will focus on river forms and patterns, river avulsion, and avulsion impacts on society. The PIs will work with the outreach offices at Penn State and Boston College to develop, pilot test, and evaluate module activities in Pittsburgh- and Boston-area schools, targeting underserved communities in each region. Finally, this proposal will also support the education and training of several graduate and undergraduate students and the early careers of two junior faculty members.