UC Santa Barbara

Determining where sediment goes and why is a problem that defines the field of geomorphology and has direct implications on the fields of soil science and ecology. The morphology of landscapes changes when they are perturbed from a balance between uplift and erosion – this leads to a state of transience where soil and sediment is shed or accumulated in order to reestablish steady-state. This dissertation looks at what happens to the landscape when the balance between uplift and erosion is upset by different timescales of perturbations: 1) tectonic uplift and sea-level rise induced base level change over tens of thousands of years and 2) human land-use induced decreases in soil cohesion over the last 200 years. I use the westernmost portion of the Transverse Range, CA for this research. Active tectonics and a spatial variation in lithology within a similar climate makes this region a natural laboratory for this work. This dissertation encompasses three, individual studies which contribute towards understanding landscape change over different timescales in the Western Transverse Range, CA. Collectively, these studies show that the interplay between climate and lithology influences the way this landscapes adjust to both long- and short-timescale perturbations to the balance between uplift and erosion. Specifically, the current semi-arid climate limits how soil is produced and where it can go in a landscape, and the erodibility of the underlying lithology sets how much soil can be produced and how erosion can be translated across catchments.