Date of Award

2012

Degree Type

Report

Degree Name

Master of Science (MS)

Department

Watershed Sciences

First Advisor

John C. Schmidt

Abstract

Stream restoration activities in Reach 6 of Blackwood Creek involved constructing a new stream channel in a reach that had been eroding and adjusting to historic land uses since the 1960s. In 2010, the spring after restoration work was completed, the project had a 2.3-year recurrence peak flow of 12.3 m3/s. This post-project assessment looks at the impacts of restoration work in Reach 6 in the short time since the project was completed. Project objectives for restoration work were to: increase the extent of floodplain inundation for seasonal flooding, reduce the rate of bank erosion, and to encourage sediment deposition, particularly fine sediment, on the floodplain. Using HEC-RAS, a one dimensional hydrologic model, I predict that the extent of flooding over a wide range of recurrences will increase as a result of restoration work, with the largest proportional increase for small magnitude, high recurrence floods. To assess the impact restoration activities will have on stream channel erosion, the average predicted shear stress was compared between pre-restoration and post-restoration conditions. This work indicates that there will be a decrease in average shear stress for all floods, with a 39% decrease for the 1.5-year recurrence flow and a 48% decrease for a 20-year recurrence flow. In 2010, areas of deposition iii and scour were mapped in Reach 6 to assess whether the project reach was accumulating sediment on the floodplain. I found that 1,129 m3 of sediment had been deposited and 142 m3 of sediment has been scoured. Of the 1,541 Mg of sediment deposited within Reach 6, 40% was gravel and coarser sizes, 50% was sand, 7% was silt, and 2% was clay.

Comments

This work made publicly available electronically on May 7, 2012.

5-7-2012

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