Semester

Spring

Date of Graduation

2007

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wood Science and Technology

Committee Chair

Jingxin Wang.

Abstract

In 1999, a study was initiated in two forested headwater channels to compare and contrast changes to in-stream suspended sediment and turbidity following the construction of a forest haul road. Turbidity (NTU), suspended sediment concentrations (SSC) (mg L-1) and streamflow (L s -1), were measured throughout May 2005. Both catchments are ephemeral/intermittent tributaries of the Left Fork of Clover Run in the Cheat River watershed. To exclude inputs of hillside sediment both catchments were continuously lined with silt fence from constructed gauging/sampling stations to the upper most portions of their drainage network. In July 2002, construction of a 0.93 km (0.58 mi) road (FS 973), encompassing 1.3 ha (3.3 ac) of the 32.7 ha (80.8 ac) treatment watershed, was initiated. FS 973 was completed in September 2003. Data were separated for comparison by road construction initiation (i.e. pretreatment and post-treatment), although, some analysis focused solely on the construction period independently. During the construction period, several tons of sediment were deposited in the stream channel. Following construction, the treatment watershed's stream turbidity, in relation to both watersheds pretreatment period and in respect to the reference watersheds post treatment period, increased significantly. While the highest turbidity value recorded in the treatment watershed (2352 Nephelometric turbidity units (NTU)) was 6.4 times larger than the highest turbidity sampled in the reference watershed, it was sampled during low streamflow (<1.4 L s-1 or <0.05 ft3s-1(CFS)). Fourteen post-treatment samples exceeded 100 NTU at discharges greater than 56.5 L s-1 (2.0 CFS) when the treatment watersheds average streamflow was 5.5 L s-1 (0.20 CFS). The reference watershed's samples stayed within expected ranges throughout the duration of this study. Turbidity increased significantly due to the construction of FS 973, specifically due to the prolonged period in a pioneered condition, construction of three culverted stream crossings, an inadequate cross-drain, and a constructed stream channel.

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