Weir Jetty Performance: Hydraulic and Sedimentary Considerations.

A hydraulic model investigation was performed to study important design parameters for a weir jetty system including weir length, elevation, orientation with respect to the shoreline and the conventional portion of the jetty structure, tidal currents over the weir section, flow patterns in the vicinity of the weir section, sediment movement over the weir and effects of the weir jetty on accretion, and erosion upcoast of the jetty system. The study was accomplished with a fixed-bed undistorted, 1:100 scale model. Large ocean and bay areas were reproduced in a 150-ft by 305-ft facility. Tides were reproduced in the model and two types of inlet-bay systems were simulated--one system in which the bay only partially fills (low Keulegan K value) and the other in which the bay only nearly fills (high Keulegan K value). The conditions provided extremes of velocity-tidal elevation flow relationships over the weir. Sediment tracers and a movable-bed beach section provided the means to examine deposition basin filling, fillet accretion patterns for upcoast waves, and fillet removal by waves from the downcoast direction for several weir jetty orientations, including weir angles with the shoreline of 30, 45, 60, and 90 deg.