1. Why Does North County Have So Much Trouble Retaining Sandy Beaches? Southern California Beach Processes Study O’Reilly, Guza, Seymour, Flick, Yates, Thomas, et al Scripps Institution of Oceanography

5. Island Sheltering Wave Refraction/Focussing “Hot Spots”

6. CDIP Buoys Wave Climate : Oceanside Littoral Cell Alongshore Wave Climate Reconstruction Incident waves Cross-shore Component Alongshore Component

7. Oceanside Littoral Cell: The “River of Sand” Wave-Driven Net Southward Sand Transport Sand Leaves Cell at Scripps Submarine Canyon

8. Wave-driven Lagoon Sub-Cells Batiquitos Sub-Cell Moonlight Sub-Cell San Elijo Sub-Cell Fletcher Sub-Cell San Diegito Sub-Cell Penesquitos Sub-Cell Torrey Pines Sub-Cell

9. Coastal Lagoon Incident waves drive net southward sand transport between lagoons. Waves refract over offshore sediment fan south of the lagoon entrance. EROSION HOT SPOT Waves focus south of lagoon entrance eroding the coast, disrupting southward sediment flow, and moving sand offshore towards the sediment fan. The disrupted net longshore transport rate increases between lagoons resulting in net longshore erosion of sand. Longshore Transport Ocean 20m depth contour COASTAL LAGOON LITTORAL SUB-CELLS 3. 1. 2. 4. The net longshore transport rate decreases rapidly to near zero in front of the lagoon, resulting in deposition of sand. 5. Cross-shore Transport shoreline 30m

10. Coastal Lagoon Sand Borrow Sites Sand feeder site to maximize residence time in lagoon cell? Ocean 20m depth contour COASTAL LAGOON LITTORAL SUB-CELLS Naturally sand-deprived section of coast along base of cliffs between lagoons? Natural Erosion Hot Spot. Artificial surfing reefs to reduce erosion & cross-shore sand loss? Sand Borrow Sites Natural clogging of lagoon entrances?

11. Conclusions We have no conclusions! We have no conclusions! We do have new ideas, models, and data. We do have new ideas, models, and data. We think it is an appropriate time to begin sharing our SCBPS research with SANDAG on a routine basis. We think it is an appropriate time to begin sharing our SCBPS research with SANDAG on a routine basis.