High Quality Content by WIKIPEDIA articles! San Diego Creek is a 16-mile (26 km) waterway flowing into Upper Newport Bay in central Orange County in the U.S. state of California. Its basin covers 112.2 square miles (291 km2) in parts of eight cities, including Irvine, Tustin, and Costa Mesa. The major tributary of the northeast-flowing stream is Peters Canyon Wash, which joins a few miles above its mouth. Now mostly channelized, San Diego Creek serves an important function for flood control, but it has been extensively monitored for sediment loads. The purpose of this studying is that Upper Newport Bay, which San Diego Creek is the primary freshwater input of, is a rich ecological habitat and preserve.