Eroding shoreline bluffs, or feeder bluffs, are a recurring dynamic geologic process that can be found along Whatcom County’s marine shorelines. Bluffs provide materials necessary for forming and maintaining our beaches, as well as supporting the geologic, biologic, and aesthetic diversity of our shorelines.
Many bluffs are naturally unstable due to soil, slope, and water conditions and are subject to periodic erosion, sliding and slumping. The natural rate of bluff erosion on Whatcom County shorelines varies and depends on several factors, including: exposure to wave action (toe erosion and undercutting), geologic resistance to erosion, and the width and elevation of the beach below.
Sand, gravel, and other materials that come from the erosion of these
bluffs nourish nearby beaches, spits, and other types of accretion
shoreforms. Protection of the natural function of these sources of beach
material is vital for the long-term stability of shoreline habitat and
Risk of more frequent or more intense bluff erosion and slides can be
aggravated by increased development and human activities. Activities
that can have potential impacts include: increased or focused drainage
concentrations such as stormwater runoff or septic drain fields, removal
of trees and vegetation, road cuts, excavation, placement of fill
materials on a slope face, and so on.
Periodic efforts to
control erosion and stabilize shoreline bluffs to protect developing
shoreline areas are complicated by the fact that most of the marine
beaches in Whatcom County consist of materials contributed by erosion of
feeder bluffs. Not only can these efforts have significant financial
impacts, but they can also lead to significant environmental impacts.
Prevention of erosion and landsliding in some areas may actually result
in considerable declines in sediment supplies that continually
replenish our beaches. A reduction in materials can essentially starve
beaches and downshore areas, leading to the loss of beaches, fish and
wildlife habitat, and accelerate erosion of previously stable areas.