Civil/Structural Engineering, Vashon, Washington, USA 206-463-5311
Ellisport Engineering Blog
Stream Erosion Protection and Habitat Restoration

When we started our company in 1988, many of our early projects were protection of waterfront homes and properties.  I’ve long had an interest in balancing the structural protection aspects with the environmental implications of shoreline hard armor installations. 


An August 23rd article in The Spokesman-Review talked about a company (Wilson Precast Inc.)  in Spokane manufacturing “dolos”, 16,000 pound concrete structures used for shoreline protection.  They’re shaped roughly like giant child’s jacks, and they’re very big


Dolo’s are an old idea dating to at least 1965.  They are interlocking concrete structures used as breakwaters for shore protection against erosion and large waves.  They’re used around the world.


Recently, dolos are being used as erosion protection and habitat restoration in rivers.  Typically, they’re clustered together with interwoven logs, stumps, and branches at strategic river points for bank protection in high water situations; there are multiple installations on the Puyallup River.  The fancy engineering term is “Engineered Log Jam”, or ELJ. 


The application of dolos to rivers is relatively new.  The Spokesman-Review’s article states, “Biologists believe the dolo timber system creates partly submerged structures where fish and wildlife can hide, while also diverting the stream to protect vegetation and banks from erosion.”


Each dolo costs about $1800; though not terribly expensive, they’re probably beyond the reach of most waterfront property owners, especially when considering the barge and crane installation costs.


Overall, I think they’re an inexpensive and creative solution to mitigate erosion problems and protect against high wave damage.  They would seem to be a good solution for tsunami protection as well. 

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