An assessment of road removal and erosion control treatment effectiveness : a comparison of 1997 storm erosion response between treated and untreated roads in Redwood Creek Basin, Northwestern California

Author

Anna L. Bloom

Graduation Date

1998

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Environmental Systems: Geology, 1998

Committee Chair Name

Mary Ann Madej

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Soil conservation, Roads, Humboldt State University -- Theses -- Geology, California, Redwood Creek, Environmental aspects, Design and construction, Watershed management, Redwood Creek Watershed

Abstract

Since rehabilitation of deforested watersheds has begun in the Pacific Northwest, published large scale evaluations of road removal and respective erosion control techniques have been brief and scarce. In 1997, a 12 year recurrence interval storm provided an opportunity to assess the effectiveness of watershed rehabilitation efforts in Redwood National Park, Northwestern California. This study compares 1997 storm erosion and resulting sediment delivery to streams between 91 miles of untreated roads and 21 miles of treated roads in the Redwood Creek basin. The treated roads yielded significantly less 1997 storm erosion and sediment delivery to streams than untreated roads. This comparison also indicated that more intensive erosion control treatments resulted in less overall 1997 storm erosion than minimal treatments; however, the difference in sediment yielded to streams is not pronounced. On stable hillslopes, minimal treatments seem effective and may be a cost effective alternative for reducing sediment input into streams. Among the more extensive erosion control treatments, export outsloping experienced significantly more erosion and resulting sediment delivery to streams than outsloping. Further investigation is recommended for more effective treatment of these road reaches where excess water is present. Fill sites experienced minor erosion resulting from post-treatment adjustments. Most of the erosion occurring on treated roads may be attributed to their location in the Bridge Creek Lineament, a zone marked by excessively sheared schist. Locations with excess water, such as a spring, produced more erosion than the other treated road segments.

https://scholarworks.calstate.edu/concern/theses/fj2364507

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