Dr. Helen Willemien Dow (maiden name: Beeson)

In this project, we exploited this idea to develop geomorphic signatures of the transient fluvial response to a variety of perturbations that move a river network away from equilibrium. We used a model composed of linked 1-D river profile evolution models to simulate the transient fluvial response to a uniform pulse of uplift, a step change in erodibility intended to simulate a change in climatic conditions, beheading of the mainstem river, and nonuniform uplift due to tilting. We simulated tilting about a horizontal axis perpendicular to the mainstem and located at the river mouth ("forward tilting"), as well as tilting about a horizontal axis perpendicular to the mainstem but located at the channel head and tilting about a horizontal axis located along the mainstem. We further simulated forward tilting over different durations and with heterogeneous lithology. We showed that each of these perturbations generate a suite of distinct signatures and that many allow for reconstruction of the timing and the magnitude of the perturbation. Lastly, we documented signatures of a rapid tilting event in a sample of rivers from Sierra Nevada, California, USA, and of a step increase in tilting rate in a sample of rivers from the Sierra San Pedro Mártir, Baja California, Mexico, two ranges thought to have been tilted westward in the late Cenozoic.