|A pair of dolosse reinforcing the harbor jetty of Crescent City, Del Norte County, California|
During summer month, waves typically are not so hazardous. Fishermen, recreationists and tourist then take the risk. Go out when the tide is going out and the seawater level drops to its low.
The jetty was built to protect the harbor of Crescent City. The dolosse you will see in great numbers toward the end of the jetty provide further protection by dissipating the energy of strong ocean waves and weakening their erosive force. A paper posted next to a path on the lighthouse islet informs about the dolosse (using a different spelling: doloes): they were put in place on the jetty in 1986 to break up the force of the water during tremendous winter storms (when you definitely do not want to be on the jetty). Each dolos (spelling on post: dolo) consists of concrete with steel rods, weighing 42 tons (84,000 lbs.). 750 dolosse are in place, 20 red ones with transmitters to monitor possible movement. Note that even a dolos with 400 times your weight (or more) may fail to stay in place when hit by a really forceful wave. Therefore, dolosse are individually numbered to track their displacement.
|A single dolos: H-shaped concrete block engineered with one side turned through 90 degrees|
Invented in South Africa, a dolos roughly has the geometry of a letter H with one side turned through 90 degrees to create the distinctive shape that ensures interlocking with each other when arranged by a crane. Although entangled, a “dolos wall” leaves holes such that wave energy gets dissipated. Depending on position and wave action, it happens that one dolos hammers a neighbor dolos into pieces.
|End of the walkable jetty: turning around at the dolos jungle|
References, resources and more to explore
 The full story behind the dolos and its SA creator. IOL, August 2016 [www.iol.co.za/news/the-full-story-behind-the-dolos-and-its-sa-creator-2055577].
 Gary L. Howell: Measurement of Forces on Dolos Armor Units at Prototype Scale [icce-ojs-tamu.tdl.org/icce/index.php/icce/article/viewFile/4381/4062].
 Diana Tolerico: Crescent City. Life on the Open Road, September 2010 [lifeontheopenroad.blogspot.com/2010/09/crescent-city.html].