Feeder bluffs are significant sources of beach sediment. Knowing the location of feeder bluffs is important for the long-term management of our coastline. Mapping helps combine what we already know with new field data to better show the distribution of feeder bluffs around Puget Sound. About 426 miles — 17 percent — of Puget Sound's shoreline are currently made up of bluffs classified as feeder bluffs or exceptional feeder bluffs.
What makes up mapping data?
Several types of geologic and topographic information sources help us map feeder bluffs.These include:
- Geologic maps that indicate bluff composition
- Slope stability maps that identify slide-prone areas and types of landslides
- Topographic data that provide bluff height and indications of erosion
Maps of coastal processes and units, such as longshore transport and drift cells, provide context and help define the area influenced by a particular bluff. Aerial photographs can give us clues about recent erosion patterns, bluff characteristics, or the presence of seawalls or other structures that might disrupt natural patterns of erosion.
Combined with field observations, maps and aerial photos provide a good picture of the distribution of feeder bluffs throughout the region.
Efforts to map Puget Sound
In 2012 and 2013, we received funding from the EPA to map feeder bluffs throughout Puget Sound and make this information publicly available.
The project combined previously collected feeder bluff data, geologic maps, and remote sensing methods with extensive new field work and analysis. Mapping shows us the character and distribution of feeder bluffs, along with other coastal land forms, for all of Puget Sound’s approximately 2,500 miles of shoreline.
How to view coastal maps
You can view our maps on the Coastal Atlas. Information can be viewed in combination with other shoreline data. Feeder bluffs are included in the Coastal Landforms data layer. The maps are also available for download on our GIS Data webpage.