Abstract

Large earthflows are a significant source of sediment in the highly sheared and easily eroded Franciscan melange of the northern California Coast Ranges. They are active during the winter wet season, and their movement averages 2.4 to 4.0 m/yr. Fluvial sediment yield from the gullied and broken earthflow surface is about equal to sediment yield by mass movement. Indirect evidence suggests that changes in vegetation cover due to grazing beginning in the nineteenth century may have increased the rate of earthflow movement.

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