Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Merced Electronic Theses and Dissertations (2009)

This research examined the in-stream sediment sources for four 1 km2 headwater catchments in the central Sierra Nevada, California. Erosion of material from two major sediment sources within headwater channels was estimated: headcut erosion and bank erosion. Repeat surveys of channel headcuts were conducted; measurements of channel geometry were used in conjunction with bank erosion measurements in a bank migration model to estimate bank erosion for the length of the channel. High amounts of variability were found in the measured stream parameters and eroded volumes both within each catchment and across the four catchments, but values were within one order of magnitude for all four study watersheds. Results also showed that though migration rates were similar in headcuts and bank bends, bank erosion totals were much higher than headcut erosion totals for three of the four catchments and roughly equal in the remaining catchment. Values ranged from 0.89 m3 to 4.24 m3 per year for total headcut erosion and 1.43 m3 to 23.61m3 per year for total bank erosion in the four study catchments. Finally, a scaled down version of a linear meander migration model based on the sediment continuity equation, shows potential as a tool for managers to estimate bank erosion, as it appears to give reasonable values using a few relatively simple to measure model inputs.

    • Article
    • Peer Reviewed
    UC Merced Previously Published Works (2014)
    Seasonal turbidity patterns and event-level hysteresis analysis of turbidity verses discharge in four 1 km2 headwater catchments in California's Sierra Nevada indicate localized in-channel sediment sources and seasonal accumulation-depletion patterns of stream sediments. Turbidity signals were analyzed for three years in order to look at the relationships between seasonal turbidity trends, event turbidity patterns, and precipitation type to stream sediment production and transport. Seasonal patterns showed more turbidity events associated with fall and early to mid- winter events than with peak snow-melt. No significant turbidity patterns emerged for periods of snow melt vs. rain. Single event hysteresis loops showed clockwise patterns were dominant suggesting local sediment sources. In successive discharge events, the largest turbidity spike was often associated with the first but not necessarily the largest discharge event-indicating seasonal depletion of local sediment stores. In multi-peaked discharge events, hysteresis loops shifted from clockwise to linear or random patterns suggesting that localized sediment stores are being used up and sufficient flow energy must be reached to start entraining the more consolidated bank/bed sediment or that dominant sediment sources may be shifting to less localized areas such as hill slopes. A conceptual model with phases of accumulation and transport is proposed.
      Top