Abstract:
The forested slopes of north coastal California drain to a dense network of
streams that provide habitat for numerous threatened and endangered anadromous
salmonid species listed under the federal Endangered Species Act. Land surface
alterations in combination with a series of large storms in the region have increased
the amount of sediment delivered to stream channels from fluvial and landslide
erosion, contributing to the degradation of aquatic habitats. With concern for the
protection of public trust resources, natural resource managers at Redwood National
and State Parks (“the Park”) work to improve landuse practices on private timber and
ranch lands upstream of the Park in the Redwood Creek watershed. Geographic
information systems (GIS)-based, physical process driven models have been
developed to delineate areas with a high potential for shallow landsliding. This
project documents the application and evaluation of one such model, SHALSTAB, in
the Redwood Creek watershed of northwestern California. Model results were
interpreted in the context of existing shallow landslides. The utility of model output
to Park resource managers was evaluated. SHALSTAB model results flagged 13% of the Redwood Creek watershed as
having a high potential for shallow landsliding. Slopes in this category, including
inner gorge slopes, were shown to capture 75% of the shallow landslides mapped
within the watershed. Model output was field tested in the Lake Prairie Creek sub-watershed of upper Redwood Creek. Model results proved instructive to Park
geologists involved in the timber harvest review process. Equipped with maps of
model output, Park geologists prioritized timber harvest plans warranting field review
and evaluated slopes of potential concern during pre-harvest field inspections. Rather
than accepting model output at face value, Park geologists rely on their professional
judgement to evaluate slope stability once on site, discussing conditions with foresters
and state regulatory agencies, and recommending mitigation measures where
warranted.
Description:
Project (M.S.)--Humboldt State University, Natural Resources: Natural Resources Planning and Interpretation, 2003