Sulphur Creek (California)

Course

The creek begins as a storm culvert exiting into daylight downstream of a shopping center near the intersection of Crown Valley Parkway and Greenfield Drive. It then flows generally south through a concrete storm channel, then diverted into another culvert that takes it underneath a small access road. For the next few miles, the creek parallels Crown Valley Parkway as it winds west and south through a valley almost entirely filled by residential development. The creek flows through a concrete channel and three more culverts before regaining its natural riverbed. At the third of these four culverts, the creek enters Sulphur Creek Park, which follows the Sulphur Creek riparian corridor to where it turns west-northwest into Crown Valley Park, just upstream of Laguna Niguel Regional Park. Here, it receives two small tributaries (Niguel Storm Drain and an unnamed creek flowing from a spring on the hillside) on the left bank. The creek then enters a box-cut concrete channel that takes it to Sulphur Creek Reservoir, a 44-acre (0.18 km²) lake about 1.5 miles (2.4 km) long, formed by a dam at its north end. At the lake, another small unnamed tributary, from a filled-in canyon on the east side, joins Sulphur Creek.

The creek then exits the dam from the concrete spillway on the east side, flowing into a small valley inside Laguna Niguel Regional Park. About 0.5 miles (0.80 km) downstream from Sulphur Creek Reservoir, it receives the water of a large storm drain on the right bank. This storm drain is responsible for much of the pollution problems in the Sulphur Creek watershed. It then flows past a small mountain on the north, known as Kite Hill, and is diverted into a large culvert underneath Alicia Parkway that drains it to a small canyon. The creek then flows into Aliso Creek, just outside the boundary of Aliso and Wood Canyons Regional Park.

Geology

About ten million years ago, much of western and southern Orange County and most of coastal Southern California was part of a warm and shallow sea. This sea receded over time, leaving a large and flat coastal plain. Over 1.22 million years ago, the uplift of the San Joaquin Hills began along a blind thrust fault that stretches north into the Los Angeles Basin, eventually rising to an average of 500 to 700 feet (150 to 210 m) above sea level, with the highest peaks topping out at about 1,000 feet (300 m). Rising at about 0.6 to 0.8 feet (0.18 to 0.24 m) per one thousand years, a series of marine terraces formed along with the hills' uplift. This uplift changed the course of Sulphur Creek to run north to Aliso Creek, instead of flowing south to Salt Creek (see Watershed).

River sediments helped to create the broad and flat terrain and river valleys between the San Joaquin Hills and the much higher Santa Ana Mountains to the east. Sulphur Creek's watershed is located in a southern area of the San Joaquin Hills where many smaller hills have formed in a wider area instead of a single, tall, narrow mountain chain. These lower hills are composed primarily of sedimentary rocks and date from the Miocene period. The oldest rocks in this area are referred to as the Vaqueros Formation, while the younger are named the Monterey Formation. This hilly area is drained by Sulphur Creek to the northwest, Salt Creek to the south, small and unnamed coastal canyons to the southwest, and small tributaries of Trabuco and Oso Creeks to the east. This area is located northwest of the San Juan Creek valley, southeast of the Aliso Creek valley, and west of the Oso Creek drainage.

Watershed

The Sulphur Creek subwatershed covers about 17 percent of the entire Aliso Creek watershed, encompassing about 6 square miles (16 km²) in the southwesternmost corner of the 35-square-mile (91 km²) Aliso Creek basin. Primarily residential, it is bordered on the north by the Aliso Hills Channel drainage area (tributary to Aliso Creek), on the south and southwest by the basin of Salt Creek, and to the west by the Oso Creek watershed, a tributary basin of the Trabuco Creek watershed. Most of the basin of Sulphur Creek is hilly, but not very mountainous, although the creek has been largely changed by human occupation. Several canyons that originally drained into the creek have been filled in with material excavated from the surrounding mountain-tops, creating smoother terrain. Many present-day storm drains still follow the original course of these canyons. About 30 percent of the creek's course has been inundated by the Sulphur Creek Reservoir, formed in the 1950s by a large dam across a broad north-trending valley.

The Sulphur Creek watershed has had a long history of water pollution, which can be attributed to residential development. While no raw sewage flows into the creek, the creek is contaminated by large quantities of urban runoff from impervious paved surfaces that collects toxins before pouring untreated into the creek. There are over four large storm drain outlets that pour directly into Sulphur Creek. Such untreated runoff has caused E. coli and Enterovirus to increasingly harm the creek and its remaining biodiversity. Channelization is also another factor, and standing water in the Sulphur Creek Reservoir has suffered eutrophication. The primary source of bacteria contamination is the largest tributary of Sulphur Creek, now mostly underground. The channel joins the creek not too far from its mouth. It has been proved that 87 percent of the Sulphur Creek mainstem is severely degraded.

History

Located to the southwest of Aliso Creek, Sulphur Creek historically lay in the territory of the Acjachemen Indian group, whose main population center was actually farther south, at the confluence of San Juan and Trabuco creeks. A nearby village, Niguili, was located near the mouth of Aliso Creek likely near the confluence of Aliso and Sulphur Creeks. Present-day Laguna Niguel takes its name from this settlement. The Acjachemen were renamed the Juaneño by Spanish priests in the 18th century, who established a mission at the present-day location of San Juan Capistrano. Following the Spanish arrival, most Juaneño clustered around the mission in the south. Like many other once widespread Juaneño villages, Niguili was likely abandoned soon after, and there is no trace of it remaining.

From 1842 to the 1960s, the entire land area was known as Rancho Niguel, a Mexican land grant originally belonging to Juan Avila. Eventually, after passing through several ownerships, the ranch was purchased in 1881 by Lewis Moulton and Jean Pierre Daguerre, who expanded it to 21,000 acres (85 km²). By the 1960s, the City of Laguna Niguel bought a large portion of the ranch from the Moulton family; it was later donated to the county for recreational use. Resultantly, the upper and lower sections of the creek are now under county ownership, and the Sulphur Creek Reservoir is managed by the Orange County Flood Control District.

In the 1950s, a large dam, about 485 feet (148 m) long and 42 feet (13 m) high, was raised across lower Sulphur Creek by the U.S. Army Corps of Engineers to create Sulphur Creek Reservoir (otherwise known as Laguna Niguel Lake). This flooded 1.5 miles (2.4 km) and 44 acres (0.18 km²) of the original course of the creek, creating a 520 acre foot (640,000 m³) impoundment. This lake was annually stocked with fish, and by the 1960s, residential communities began to rise on the hills west of the main (southward-flowing) segment of the creek, while increasingly contaminated urban runoff began to contribute to the creek's flow. These hills originally consisted of high, narrow ridges dissected by steep but shallow and short canyons but were leveled to make way for buildings. In 1973 the 236-acre (0.96 km²) Laguna Niguel Regional Park was established in the lower third of the creek course, covering the extent of the creek from the head of Sulphur Creek Reservoir to where the creek crosses Alicia Parkway through a large culvert. In 1990 the final reach of the creek became part of Aliso and Wood Canyons Regional Park.

Wildlife and flora

Historically, the Sulphur Creek watershed was mostly hilly terrain consisting of chaparral and coastal sage scrub, with native riparian vegetation, likely consisting of live oak, sycamores, and alders (the namesake of Aliso Creek; Aliso is the Spanish translation of Alder) and other small trees, lined the small and seasonally flowing creek. Fish were likely nonexistent in the historic Sulphur Creek watershed - although Aliso Creek was perennial, steelhead trout were found to not have inhabited Aliso Creek even during flow periods, despite claims of some residents. (See Wildlife of Aliso Creek for a detailed explanation on the absence of steelhead.)

With the introduction of non-native species, predominantly giant reed, castor bean and tobacco tree, native plant species in the watershed began to die out. As giant reed is not suitable habitat for many species, areas infested by giant reed are biologically dead in comparison with unaffected areas. It can grow extremely fast, removing too much water from the creek, and during flood events, many parts of the giant reed can wash downstream and re-establish themselves as a new colony, increasing the problem. Along with increasing concentrations of nutrients from fertilizer and other substances contained in runoff, algal blooms began to hurt the water quality of the creek, especially above Sulphur Creek Reservoir. The historically seasonal creek was replaced with a constant flow of polluted water from several large storm drains and many smaller ones. Fish thrived for a limited time in Sulphur Creek between the introduction of perennial flows and the devastating floods at the end of the 20th century. These floods wiped out many of the remaining riparian areas lining waterways in the watershed. Despite the massive environmental degradation in the Sulphur Creek watershed, it is not biologically dead, yet and still supports some native species. Work is under way in the watershed to remove non-native species and restore native riparian vegetation.

Aliso and Wood Canyons Regional Park, which is located at the lower extreme of Sulphur Creek, supports far more native species than the Sulphur Creek watershed (see Wildlife of Aliso Creek for detail).

Recreation

Sulphur Creek Reservoir is the primary recreational facility in the watershed and is said to be one of the largest fisheries of Southern Orange County. The lake is annually stocked with bluegill, catfish, and bass. Aside from the reservoir, there is no body of water in the watershed that is navigable. There are several other parks in the watershed; these are Crown Valley Park, Sulphur Creek Park, and others. A paved trail follows Sulphur Creek from near the terminus of Crown Valley Park to near its mouth at Alicia Parkway.

Etymology

The Geographic Names Information System lists "Arroyo Salada" (Spanish: Salt Canyon) as a variant name. Cañada Salada, translated to "Valley of Salt" or "Salt Canyon" (Durham's Place Names of the Greater Los Angeles Area, 2001) is another name for the lower section of the creek. These names, dating to Spanish times, imply that the creek was naturally salty or briny. As Salt Creek to the south bears a name of similar meaning, and that the "Arroyo Salada" Storm Channel occupies the lower section of the prehistoric Sulphur Creek watershed, there is further proof by salt concentrations that the two watersheds were once linked (see Watershed).