24Sep2024 – This month we are honored to have Dr. Karin Lehnigk, Postdoctoral Researcher at Georgia Tech, as our speaker.
Upper Grand Coulee, the largest flood-carved canyon in the Channeled Scabland, has long intrigued scientists and non-scientists alike. Due to its large size, researchers have thought that it likely took multiple glaciations to incise upper Grand Coulee. However, recent geochemical dating and hydraulic simulations of flooding in and around upper Grand Coulee suggest that the canyon was carved by <10 floods, and that this erosion took place entirely during the last Ice Age. The young age and rapid growth of upper Grand Coulee indicates that the Missoula Floods were exceptional agents of landscape change, even compared to other highly-erosive events.
The Channeled Scablands of eastern Washington is a perfect location to see how surface processes have changed the appearance of the landscape. Huge glacial outburst floods during the last ice age (Fraser) carved impressive canyons into the basalt bedrock, and the ice, water, and deposited sediment have left a complicated trail to decipher. Karin performed cosmogenic nuclide exposure dating on flood-transported boulders to determine what path the floods took at different points in time. Additionally, she simulated individual flood events by hydraulic modeling over various topographic reconstructions, to constrain the discharges of these floods. Her previous work has focused on river network geometry, using the shapes of fluvial networks on Mars to understand how volcanic activity influenced the movement of water during episodic meltwater floods.
Originally from Virginia, Karin was drawn to geomorphology by the range of landscapes she encountered throughout the Mid-Atlantic. She completed her PhD at UMass Amherst, where she studied the landscape impacts of outburst floods in the Channeled Scabland, as well as in Nepal and Norway. She is currently investigating water/sediment interactions in outburst floods in the Himalaya and on Mars, as well as hazards from modern dam-break floods, as a postdoc at Georgia Tech.