Guidelines Based on Physical and Numerical Modeling Studies for Jetty Spur Design at Coastal Inlets

A jetty spur is a relatively short structure that extends from the beachside of a jetty and diverts sediments from entering a navigation channel. A series of physical model laboratory tests with waves and currents was conducted in that varied spur length, spur crest elevation relative to the jetty structure, and spur orientation. Wide and narrow breaker zones were simulated. These experiments were augmented with numerical modeling that coupled waves, depth-averaged current, sediment transport, and morphology change at an inlet. Results indicated that a submerged spur was as effective as a surface-piercing structure in deflecting the seaward-moving current along the jetty, potentially saving construction and maintenance costs. Also it was noted that if the angle of the spur was such that the approaching waves broke initially at the seaward end and progressed breaking in an upcoast direction along the spur face, the ability to deflect a current moving along the jetty axis was enhanced. Recommendations for jetty spur location, elevation, length and angle are discussed.