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

BIGFOOT: BIG-storm FOOTprint on California and future hazards



Surficial Geology Map of Unconsolidated Materials

The distribution of surficial materials and their physical properties exert strong controls on landscapes including erosion processes, ecosystems, and long-term landscape evolution. Large-footprint storms will likely generate floods in steep upland hillslope environments. In these environments, the response to large storms will depend on the physical properties of the materials on the slopes. How much water infiltrates or is partitioned to runoff, how much sediment is available to be mobilized as sheet or channelized flows, debris flow or landslides are all determined by the hillslope soils. However we currently have no means of effectively mapping these soils, nor the important characteristics of these soils. The interplay between hillslope soils and their underlying bedrock also effect other processes such as long term erosion rates, soil moisture available to ecosystems (important for fire threats, climate change resilience, etc) and groundwater recharge.

Objectives: To make maps of surficial geologic materials and their physical properties, with emphasis on steep upland catchments. The important physical properties will likely include depth to bedrock, infiltration capacity, cohesion, soil texture, and erodibility. The maps can be used to assess the likelihood for flooding and erosion as well as other applications. We will use a combination of traditional geologic mapping techniques, field and laboratory sampling, and spatial analysis. New techniques for mapping and describing spatially variable soil properties will be developed using a combination of field observations and measurements, with spatial analysis. In more mesic environments, it has been shown that steep upland soil properties vary with topographic/terrain attributes from Digital Elevation Models. The utility of combining terrain analysis to extrapolate measurements and field observations will be determined and, where possible used to the fullest extent. Field measurements will include traditional geologic observations as well as physical properties. Soil pits and probes will be used to determine soil depth, infiltrometers to determine infiltration capacity, grain size analysis and geotechnical methods to determine soil texture and mobility will be also utilized.


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