Madrona Marsh

The Madrona Marsh Preserve, in the city of Torrance in the South Bay region of Southern California, is a seasonal wetland with vernal pools. The 43 acres was a former site of oil wells and is one of the few natural areas remaining within an urban landscape.
Formed eons ago when the mountains of the Palos Verdes Peninsula rose to the south, Madrona Marsh is a shallow depression fed by wet season storms as the name "vernal" indicates. After the rainy season, evaporation, percolation and transpiration reduce the water depth by about one-quarter of an inch per day. By the end of August, the wetland is dry and remains so until the following rainy season. Situated on land that was set aside for oil production in 1924, Madrona Marsh was never developed while the city grew up around the site and remains a valuable natural habitat for birds, reptiles, insects and small mammals.

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