Sirevag Berm Breakwater, Design, Construction and Experience after Design Storm

Sirervag harbor is located in a narrow bay on the west coast of Norway approximately 50km south of the city of Stavanger. The area outside the harbor is an open coast with no reefs or shoals that give shelter from waves. The wave height reducing effects are refraction and in shallow water also wave breaking. A new breakwater was constructed in Sirevag, which started in January 200 and ended in July 2001. The primary reason for the new breakwater was to give better protection of the harbor and to improve the sailing conditions in and out of the harbor. The breakwater was designed and constructed as a statically stable Icelandic type berm breakwater for a wave height with a 100-year return period. The design 100-year recurrence wave height at the location of the breakwater was established as H(s,100) = 7.0m. During the first winter in service the breakwater experienced a storm reaching the design level. The breakwater survived the storm without any reshaping. However, stability model tests showed that there should have been a marked recession of the berm. The apparent discrepancy between the model test results and the field behavior of the Srevag berm breakwater are discussed in this paper.