This study will assess watershed conditions prior to significant Euro-American modification, as a basis for understanding subsequent changes in watershed structure and function, and potential options for future environmental management.

The tidal-terrestrial transition zone has been recognized as an important component of the San Francisco Bay, and has been identified as a high priority for restoration in the South Bay and for the Bay as a whole. This project reconstructs the approximate extent of the South Bay T-zone and characterizes it in terms of the adjoining terrestrial and intertidal habitat types and features that were historically prevalent in the region.

The study area encompasses the estuarine and alluvial portions of the Tijuana River watershed from the river mouth in southern San Diego County to the U.S.-Mexico international border. Limited research will also be conducted on an approximately 10 mile stretch of the river extending through Tijuana, Mexico.