River Mouths, Brakish and Estuarine Coastal Wetlands
I. West coast vs. East Coast River Mouths

East coast rivers dump into large estuaries distributed from Canada to the Florida everglades. They drain broad coastal plains where watersheds extend hundreds of miles inland, catching rainfall and other drainage water from extremely large geographic areas. These rivers commonly flow throughout the year; river mouths are perennially open to the sea; and estuaries extend along the shore for great distances. Since significant amounts of river water are always present, humans are relatively unlikely to develop property beyond the river banks.

West coast rivers are very different, especially from northern California into Baja California. They typically drain very narrow and steep coastal watersheds covering much less geographic area than the east coast watersheds. The exception is the San Francisco Bay which receives drainage water from the Central Valley. Most rivers from central and southern California are often dry or closed to the sea in the summer and opened each winter with tractors.

Since the rivers are often dry, humans commonly encroach into river corridors and have severely degraded water resources (California Coastal Commission 1994). For example in the Salinas Valley almost every creek, river and marsh has been ditched into a narrow channel system devoid of vegetation, native or not. Salt water intrudes into the 180 and 400 foot aquifers ten miles into the valley (Greene 1970, Johnson 1983). The entire landscape has been dramatically shifted towards a desert in the last 150 years (Gordon 1996). Yet the California coast is similar to other warm temperate regions around the planet, where fresh water is often the most limiting natural resource to human beings and natural ecosystems (National Research Council 1992, Runnels 1995, Gordon 1996).