Puget Sound Feeder Bluffs photo

Puget Sound Feeder Bluffs

Feeder Bluff Mapping

Some bluffs, due to their height, erosion rate, or composition may be more significant sources of beach sediment than others. Knowing where these feeder bluffs are located is important information in the long-term management of our coastline. The purpose of mapping is to combine various sources of existing information with new field data to better map the distribution of feeder bluffs around Puget Sound.

There have been efforts in the past to delineate eroding bluffs on Puget Sound. In the 1970s, the Coastal Zone Atlas of Washington attempted to map sediment sources, but methods and criteria were not well documented. In the past decade, a number of county-scale projects have been carried out, although sometimes with slightly different objectives or methods. Until our most recent project (described below), we have lacked a complete dataset for all of Puget Sound.

A number of different types of information can be used to characterize and map coastal bluffs.  These are summarized in:

Double Bluff on Whidbey Island is one of the region’s classic examples of an exceptional feeder bluff.

2013 Mapping Project

In 2012 and 2013, Ecology received funding to complete the mapping of feeder bluffs throughout Puget Sound and to make this information available on the Coastal Atlas website. The funding was received from the Environmental Protection Agency, and was administered through the Puget Sound Marine and Nearshore Grant Program at Washington’s Department of Fish and Wildlife and Department of Natural Resources (see Acknowledgements).
 

The mapping was carried out by Coastal Geologic Services, a geologic consulting firm based in Bellingham, Washington. The mapping project combined previously collected feeder bluff data, geologic maps, remote sensing methods, with extensive new field work and analysis. The result was a map showing the character and distribution of feeder bluffs, along with other coastal landforms, for all of Puget Sound’s approximately 2500 miles of shoreline.

For more detailed information on how the mapping was carried out and on the structure of the resulting geographic database, see the full report: Feeder Bluff Mapping of Puget Sound (PDF, Coastal Geologic Services, 2013).

Feeder Bluff Maps In the Coastal Atlas

The new maps are available online at the Department of Ecology’s Coastal Atlas, where the information can be viewed in combination with other shoreline data. Feeder bluffs are included in the Coastal Landforms data layer. (These maps are also available for download at Ecology’s GIS Site under Feeder Bluffs and Landforms.)

The emphasis of this project was on delineating and characterizing coastal bluffs, but the nature of the study and the additional field work also allowed the completion of landform mapping for the entire shoreline. This includes coastal landforms such as barrier beaches (accretion shoreforms), rocky shores, estuarine shorelines, and artificial coastal features, along with feeder bluffs. For more on these, see:

These maps of coastal landforms are complemented by other geographic data already available on the Coastal Atlas, including littoral drift, slope stability, and oblique aerial photographs, in addition to many other types of information.


Example of landform maps from Coastal Atlas, showing central Whidbey and Camano Islands. Blue and purple represent feeder bluffs, yellow symbolizes spits and other accretion shoreforms, and red denotes beaches armored with bulkheads and revetments.

Distribution of Landforms on Puget Sound

These maps provide a broad accounting of different landforms on Puget Sound, as well as a more detailed look at the distribution of feeder bluffs within Puget Sound.  An overview of the mapping results is provided in:

 

 

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