Silver Strand Littoral Cell extends from Point Loma (26 km or 16 mi on the US side of the international border) to Ensenada, Mexico. The major sediment source was the Tijuana River, with a watershed area of 4,465 sq km (1,725 sq mi), but dams have caused a 72% reduction in beach sand supply. The US portion of the cell is unusual in that transport is northward due to the wave shadow of Point Loma. Zuniga Jetty, completed in 1904 to stabilize the entrance to San Diego Bay, has altered the cell’s transport path. Sediment sinks are Zuniga shoal and an offshore cell in deep water. The bay is not a sink because its tidal prism and tidal range induce self-scouring tidal currents at the entrance and send sand offshore. Hence the importance of not altering the tidal prism of the bay. Most of the Silver Strand consists of low dunes only 3 m in elevation, making storm overwash and sea level rise a future concern.