Dynamics of an Emergency Jetty Repair at Coos Bay, Oregon

Abstract

The jetties and surrounding dynamics at the entrance of Coos Bay, Oregon form a unique and complex system that requires a systematic and comprehensive approach to its management. The deterioration of the north and south jetties due to channel deepening and movement, erosion of shoal foundation, lack of maintenance, and an increase in wave climate caused a breach of the north jetty at its root in November 2000. The emergency repair of the north jetty that followed provides an example of how the features and individual processes at work in an area can and must be incorporated into the successful design and maintenance of its structures. The evolution of the breach at Coos Bay can be used as a learning tool to show that it is imperative to understand the sediment pathways and their effect on navigation structures in order to maximize the efficiency and durability of a jettied entrance. This paper reviews the conditions that let up to the jetty breach, the emergency repair methods used at the north jetty, and the issues and concerns that will influence the decisions made about the future maintenance of the navigation entrance at Coos Bay.