Laguna Niguel Regional Park. From there, Aliso Creek turns west and enters Aliso Canyon, a nearly deep gorge which cuts through the San Joaquin Hills approaching the Pacific. About a mile (1.6 km) below Sulphur Creek, Aliso Creek is impounded at a small concrete dam. It then receives its second largest tributary, Wood Canyon Creek, to the south of Soka University of America. Below Wood Canyon it turns south, winding through the wilderness park then turning west at the South Orange County Wastewater Agency (SOCWA)'s Coastal Treatment Plant. It then flows through the former Aliso Creek Inn and Golf Course (now The Ranch at Laguna Beach), under Pacific Coast Highway, and empties into the sea at Aliso Beach in Laguna Beach. Aliso Creek forms a narrow tidal lagoon just above its mouth at Aliso Beach. The lagoon originally covered a large area at the outlet of Aliso Canyon, dammed by a sandbar that only breached during the rainy season. Due to development of the golf course and parking lots at the mouth of the creek, the lagoon has been significantly reduced from its original size. The increased freshwater inflow caused by urban runoff has further disrupted the hydrologic regime of the lagoon, which occasionally breaches causing large surge flows into the Pacific Ocean before the sandbar re-forms. Hydrology Aliso Creek was historically a seasonal stream with a few sections containing water year round, including the headwaters and lower Aliso Canyon. Significant flow only occurred in the rainy months of November through March. As recently as 1982, the creek was observed to be dry in the summer. As of 2012, urban runoff contributed a dry season flow of 5 million gallons (20,000 m3) per day, or approximately , at the creek's mouth. Urban runoff accounts for at least 80 percent of the creek's dry season flow. The United States Geological Survey operated a stream gage on the creek at the El Toro Road bridge in Mission Viejo from 1930 to 1980. This gage measured runoff from , or 26 percent of the watershed area. There was also a gauge in Laguna Beach which measured runoff from the entire watershed, but it operated only from 1982 to 1987. The average annual flow at El Toro was , ranging from in February to in July. The highest peak flow was on February 24, 1969. At the Laguna Beach gage, the average annual flow