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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #173606
Title: INFLUENCE OF TWO WOODY RIPARIAN SPECIES ON CRITICAL CONDITIONS FOR STREAMBANK STABILITY: UPPER TRUCKEE RIVER, CALIFORNIA

Author
item Simon, Andrew
item POLLEN, NATASHA - 6408-05-10
item Langendoen, Eddy

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2005
Publication Date: 2/1/2006
Citation: Simon, A., Pollen, N.L., Langendoen, E.J. 2006. Influence of two woody riparian species on critical conditions for streambank stability: Upper Truckee River, California. Journal of the American Water Resources Association. 41: 99-113.

Interpretive Summary: Over the past 35 years, water clarity has decreased in Lake Tahoe, partly due to the delivery of sediment from upland and channel erosion. A recent study (Simon et al., 2003) showed that the Upper Truckee River is the largest contributor of sediment to Lake Tahoe with a large proportion of the sediment coming from streambanks. This study combines field data with numerical modeling to identify the conditions that cause banks along the Upper Truckee River to fail. Bank failures occur during winter and spring months, brought on by repeated basal melting of snow and rain-on-snow events. Field study of young lodgepole pines and Lemmon's willow were used to quantify the effects of riparian vegetation on streambank stability. Lemmon's willow provided much more root-reinforcement (5.5 kPa) than the lodgepole pines (0.5 kPa), with the hydrologic effects of the species varying in time and space. Overall, Lemmon's willow provided a significant increased in bank strength, reducing the number of bank failures and delivery of sediment to the Upper Truckee River.

Technical Abstract: Over the past 35 years, a trend of decreasing water clarity has been documented in lake Tahoe, attributable iin part to the delivery of fine-grained sediment emanating from upland and channel erosion. A recent study (Simon et al., 20030 showed that the Upper Truckee River is the single largest contributor of sediment to Lake Tahoe with a large proportion of the sediment load emanating from streambanks. This study combines field data with numerical modeling to identify the critical conditions for bank stability along an unstable reach of the Upper Truckee River, California. Bank failures occur during winter and spring months, brought on by repeated basal melting of snow packs and rain-on-snow events. Field study of young lodgepole pines and Lemmon's willow were used to quantify the mechanical, hydrologic and net effects of riparian vegetation on streambank stability. Lemmon's willow provided an order of magnitude more root-reinforcement (5.5 kPa) than the lodgepole pines (0.5 kPa), with the hydrologic effects of the species varying spatially and temporally. Overall, Lemmon's willow provided a significant increase in bank strength, reducing the frequency of bank failures and delivery of fine-grained sediment to the study reach of the Upper Truckee River.