Decadal to Millennial-Scale Erosion Rates in South-Central California

Bookhagen, Bodo; Meelack, John; Potapenko, John; and Perroy, Ryan
[email protected]

Landscape denudation in southern California is controlled by the interplay of tectonics, lithology, climate, vegetation, and anthropogenic influences. The relative importance of these driving factors changes with the timescale considered. In this study, we present landscape-denudation rates from different timescales and we evaluate the importance of high-impact events (e.g., wildfires, rainstorms) on long-term (>104 yr) mass fluxes. Our methodologies include repeated airborne and ground-based lidar, cosmogenic nuclide inventories and geostatistical analyses. We quantify short-time scale erosion events from the Santa Barbara foothills and Santa Cruz Island using sediment flux measurements and repeated lidar surveys. We show that short-lived events with significant landscape disturbances have large impact on channel evolution, especially in the form or arroyo formation and channel-head migration. For example, wildfires followed by rainstorms resulted in rapid lowering of the channel base level that ultimately lead to arroyo formation throughout the Mission Canyon area in the Santa Barbara Foothills. On longer timescales (~104 yr), catchment-mean erosion rates derived from cosmogenic nuclides follow roughly landscape steepness, irrespective of vegetation cover and lithology. We attempt to link sediment fluxes into the Santa Barbara Channel with centennial-to-millennial scale sedimentary archives.

AAPG Search and Discovery Article #90162©2013 Pacific Section AAPG, SPE and SEPM Joint Technical Conference, Monterey, California, April 19-25, 2013