Rodeo Lagoon

Rodeo Lagoon is a coastal lagoon located in the Marin Headlands division of the Golden Gate National Recreation Area, which is in southern Marin County, California. This brackish water body is separated from the Pacific Ocean by a sand bar that forms Rodeo Beach. Rodeo Lagoon stretches approximately 900 meters (3000 ft) by 250 meters (820 feet), and is about 2 meters (6.6 ft) deep at its maximum depth. It covers a surface area of about 15 ha (37 acres).Inflows and outflowsRodeo Lagoon empties into the Pacific Ocean when the water level reaches a high enough level to erode through the sand bar. This high water level usually occurs in the winter months. The outlet channel, shown at left looking southeast towards Rodeo Lagoon, is spanned by a pedestrian bridge that provides access to Rodeo Beach. Like many other coastal lagoons in California, the outlet becomes completely blocked by a sand bar during the dry summer months, resulting in negligible exchange between the lagoon and ocean during that time.The depth, surface area, and volume of the lagoon all vary depending on the configuration of the sand berm (high or low) and rainfall (wet or dry). Depths in the center range from less than 1.5 meters (5 feet) in a dry summer to nearly 3 meters (10 feet) in a wet winter.Tides do not have a significant effect on the circulation of water in Rodeo Lagoon. Instead, the circulation of water in Rodeo Lagoon is driven almost entirely by the wind. Since the Marin Headlands are often quite windy, it is not unusual to see Langmuir circulation form windrows of foam on the surface of the lagoon.