USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
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Methodology to predict total and fine sediment load reductions as a result of channel restoration in Lake Tahoe streams

Bank erosionPrincipal Investigator:
Nicole Beck, 2NDNATURE, LLC

Proposal [pdf]

Final Report [pdf]

Data Collection Sampling Plan [pdf]

Please contact Dr. Nicole Beck with questions regarding the final report and sampling plan.

Project Summary

Resource managers need tools to quantify the water quality benefits of stream environment zone (SEZ) restoration efforts in a manner comparable to and consistent with the stormwater quality load reduction tools that have been developed to support the Lake Tahoe Total Maximum Daily Load (Lahontan Regional Water Quality Control Board [LRWQCB] and Nevada Division of Environmental Protection [NDEP] 2010) and Lake Clarity Crediting Program (LRWQCB and NDEP 2009).

It is assumed that SEZ restoration actions that increase the frequency and duration of overbank flow events may result in substantial removal of the pollutants of concern, particularly fine sediment particles (FSP <16 μm), yet to date an accepted method for estimation and supporting data do not exist. This research provides a cost‐effective data collection and analysis technique that quantifies the fine sediment particle load reductions as a result of floodplain inundation, and this analysis shows that stream restoration is a potentially significant FSP load reduction opportunity.

This research provides evidence that FSP retention by floodplains does occur and may provide a significant FSP load reduction during overbank flow events. However, the load reduction estimates provided are not yet directly comparable to an estimate of load reductions achievable by stream restoration for Tahoe streams. The data from one floodplain over 3 water years is limited in both its spatial and temporal resolution; however it is a site‐specific and representative dataset, which is very challenging to obtain given the infrequency of overbank flow events.

This research only addressed the FSP retained on the floodplain, and does not include the expected FSP load reduction associated with reduced channel erosion. There are a number of critical components yet to be resolved, but the knowledge gained and lessons learned from this research will be applied to the continued development of a Stream Load Reduction Tool (SLRT) by the 2NDNATURE team. Upcoming research will explore methods to integrate both site‐specific and readily available regional data with critical geomorphic and FSP fate and transport principles and to provide resource managers with a reasonable approach to consistently predict the FSP load reduction expected from stream restoration actions in the Tahoe Basin.