RAPID: Effect of massive, exceptional floods on sediment-associated isotope concentrations - implications for sediment source identification and erosion rate estimation

Skidmore College, Saratoga Springs NY

Investigators

Abstract

In response to unprecedented 2011 floods in southern Africa, this RAPID project will sample isotope concentrations in recently transported fluvial sediments in Namibia before these sediments are disturbed in the subsequent rainy season. With the 2011 'flood of record' occurring over much of the area that has been sampled on three previous occasions in the past 14 years, this project seizes a unique opportunity to test a fundamental (and virtually untested) assumption underlying the inference of basin-scale erosion rates from in situ Berilium-10 concentrations--that nuclide concentrations at a given location are consistent over time, even after major flood events. The PIs will also test inferences made about sediment sources from other sediment-associated isotopes (meteoric 10Be, 210Pb and 137Cs). Understanding the temporal variability of in situ 10Be and meteoric 10Be, 210Pb, and 137Cs concentrations in river sediment, as well as how each isotopic system responds to massive storm events, is a prerequisite to applying these isotopes responsibly as sediment tracers and erosion rate monitors. Sediment-associated isotopes of 10Be, 210Pb, and 137Cs are popular and widely applied for such purposes, yet their interpretation depends on whether or not nuclide concentrations are consistent over time at a given location. This project will provide a test of this key assumption.