Laguna de Santa Rosa
Diagram of the original course of the Russian River thousands of years ago when it emptied directly into the San Pablo Bay. An earthquake in the Petaluma area changed the land, reversed the flow of the Russian River back north. The new river channel became a shallow lake and marsh system. 6000 years ago the first Indians settled by the laguna. In the early 1800s the European settlers developed the laguna for agriculture and drained and channelized much of it, and removed the riparian forest. Now the Laguna de Santa Rosa is a fresh water marsh.