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GMEG - Geology, Minerals, Energy, & Geophysics Science Center

BIGFOOT: BIG-storm FOOTprint on California and future hazards

 

 

Terrestrial Climate and Sedimentation Records

Varved sediment records from the Santa Barbara Basin (SBB) suggest the recurrence of large storm and related flood events in southern California at ~200 yr intervals. Evidence for these events comes from distinct gray, inorganic horizons, which are interpreted as flood deposits from the Ventura and Santa Clara Rivers. One complication with the data from the Santa Barbara Basin record is the difficulty in determining whether or not the clay layers are indeed a result of flood events or, rather, are reworked sediment from the nearby coastal shelf. If the clay horizons in the SBB sediment column derive from flood events, there should be a signal of recurrent large storms recorded in onshore sites. To date, there has been little effort to identify and examine onshore sites that might replicate the climate signal in the SBB record to test the author's conclusions.


The primary objective of this task is to identify evidence for large storm/flooding events in sediment cores from onshore sites in central and southern California. Paleoclimate records of sufficient temporal resolution (annual-decadal) will provide us with the ability to analyze landscape response to such events at a watershed scale by quantifying changes in erosion, vegetation, fire frequency, and limnologic conditions. This will allow us to

  1. test conclusions that recurring gray/inorganic layers in the SBB sediment column represent deposition from large flood events from the Ventura/Santa Clara Rivers,
  2. more fully understand site specific responses and thresholds to large storm/flooding events
  3. extrapolate observed responses, to the degree possible (tying in with other task results from watersheds with similar geologic frameworks), to more fully understand hazards and landscape processes.

We also seek to place the impacts of large storm/flooding events in the larger context of late Holocene climate variability and anthropogenic impacts. By correlating temporally short, high-resolution records with longer time series of climate variability, we can assess the relationship between recent climate anomalies (Medieval Warm Period, Little Ice Age) and large storm/flooding events in California. This will greatly increase our ability to predict impacts of projected climate change associated with greenhouse gas emissions. Finally, the suite of sediment cores involved in this study will span the period of European contact in California and, as a result, contain proxy evidence of landscape response to dramatic shifts in land use. By using the arrival of non-native pollen in the sediment sequence to constrain this transition, we will be able to measure how the resultant changes in vegetation and fire frequency affected watershed response to large storm/flooding events.

Highlights and Key Findings:

We reconnoitered a number of small to mid-sized lakes in the Santa Barbara area that hold potential to provide evidence of climate variability on a variety of temporal scales. Natural lakes are rare in coastal CA and these sites will provide the framework for developing a record of regional climate variability and, where possible, a history of large storm events to compare with the marine record from the Santa Barbara Basin. Results from this preliminary sampling (Figure 11 A, B) will determine which sites are best suited for a more robust coring effort in the future.

Preliminary coring of Lake Los Carneros in Goleta, Examination of core stratigraphy for continuous record.
Preliminary coring of Lake Los Carneros in Goleta. Examination of core stratigraphy for continuous record.

 

   

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