Assessing Geomorphic Change in Support of Science-Based Restoration, Trinity River, CA

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Historic landuse, dam construction, water storage and flow diversion within the Trinity River watershed resulted in downstream geomorphic changes that simplified the river planform and lead to dramatic losses of salmonid habitat and significant population declines. The Trinity River Restoration Program (TRRP) requested the USGS complete an assessment of geomorphic change that could be used to inform the Phase 2 planning process for additional restoration work. This project is proposed to conduct a geomorphic assessment of the upper 42 miles of the mainstem Trinity River to quantify geomorphic change related to river restoration actions mandated in 2000 as part of the Mainstem Trinity River Fishery Restoration Final EIS/EIR Record of Decision (USDOI, 2000).

Map of Trinity River Watershed.

Map of Trinity River Watershed.

(Public domain.)

The cumulative influence of restoration actions on river geomorphology will be assessed by quantifying the nature, rate, and extent of geomorphic change throughout the 42-mile TRRP restoration reach during pre and post restoration time periods. Local conditions promoting active alluvial features will be identified and if possible documented changes will be related to both anthropogenic work and natural drivers of geomorphic change.

Activities for this program include: review of existing data ; study plan development; geomorphic mapping using historic aerial photography and topographic surveys; and estimation of the nature, extent and rates of geomorphic change.