Newport and Tijuana Site Orientation Map

San Diego Creek drains a 112.2 square mile (291 km²) basin in Orange County, California and empties into Newport Bay. Newport Bay consists of a distinctly different lower and upper bay. The lower bay is a pleasure craft marina surrounded by dense development, and the upper bay is one of three state ecological reserves in southern California owned and managed by the California Department of Fish and Game. The Ecological Reserve is home to six federally- and state-listed threatened and endangered bird and plant species and is also a major asset for active recreation in the San Diego Creek watershed.

Flooding around Newport Bay can be triggered in several ways. Inland flooding can be caused by excess streamflow that spills out of the San Diego Creek channel and into the neighboring floodplain. Around Newport Bay, flooding is caused by high embayment water levels that result from a combination of high tides, positive ocean level anomalies from storms and/or inter-annual phenomena such as El Niño, and streamflow from San Diego Creek. Along the ocean facing Balboa Peninsula, flooding is caused by waves that run up and overtop the beach, typically during periods of coincident high tides and waves. The most severe flooding occurs with coincident streamflow, rainfall, high tides, positive sea level anomalies and waves. Currently, the region is experiencing flooding on an annual to decadal basis, including major flooding of Balboa Island and Balboa Peninsula in 1983 and 2005, and significant flooding of Balboa Peninsula in 2011 from a strong southerly swell superimposed on a high tide.