Double Bluff on South Whidbey Island is a classic feeder bluff, constantly sloughing sand. Photo: Pedersen
Feeder Bluff Survey

In 2006, the MRC contracted Jim Johannessen of Coastal Geologic Services Inc. to complete a comprehensive survey of feeder bluffs and accretion shoreforms along the entire shoreline of Whidbey and Camano islands.

The forage fish that form an essential link in the marine food chain rely on beach gravels of a specific character for optimum spawning conditions. Much of the Island County shoreline, with its glacially-carved high bluffs, provides a constantly replenishing supply of these gravels through natural erosion unless human activity interferes. We engaged Johannessen to map these feeder bluffs and related accretion shoreforms on both islands.

Johannessen not only conducted new field work but also reviewed historical data, aerial photography, maps and atlases. He compared the Beach Watchers' bulkhead inventory with the location of feeder bluffs to help assess the degree of impairment - sediment impoundment - for each drift cell.

Johannessen also developed a protocol for quantitative analysis of individual segments of feeder bluff. This included development of a systematic analysis that assesses the relative input of different size sediment from bluff to beach as well as the amount of mapped beach habitat (such as forage fish habitat mapped by others) maintained by the sediment input. The protocol, when implemented, produces a ranking for specific feeder bluff segments that indicates the relative value of the segment for the overall integrity of the mapped habitats.

The new information better equips the MRC to prioritize future restoration and conservation opportunities. During the course of Johannessen's survey he identified more than 100 sites worthy of future consideration. 

Feeder Bluff Survey