Aliso Creek (Orange County)
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Aliso Creek is a -long, mostly
urban stream An urban stream is a formerly natural waterway that flows through a heavily populated area. Urban streams are often polluted by urban runoff and combined sewer outflows. Water scarcity makes flow management in the rehabilitation of urban stream ...
in south Orange County,
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
. Originating in the
Cleveland National Forest Cleveland National Forest encompasses 460,000 acres (), mostly of chaparral, with a few riparian areas. A warm dry mediterranean climate prevails over the forest. It is the southernmost U.S. National Forest of California. It is administered by ...
in the
Santa Ana Mountains The Santa Ana Mountains are a short peninsular mountain range along the coast of Southern California in the United States. They extend for approximately southeast of the Los Angeles Basin largely along the border between Orange and Riverside ...
, it flows generally southwest and empties into the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...
at
Laguna Beach Laguna Beach (; ''Laguna'', Spanish for "Lagoon") is a seaside resort city located in southern Orange County, California, in the United States. It is known for its mild year-round climate, scenic coves, environmental preservation efforts, and ...
. The creek's
watershed Watershed is a hydrological term, which has been adopted in other fields in a more or less figurative sense. It may refer to: Hydrology * Drainage divide, the line that separates neighbouring drainage basins * Drainage basin, called a "watershe ...
drains , and it is joined by seven main
tributaries A tributary, or affluent, is a stream or river that flows into a larger stream or main stem (or parent) river or a lake. A tributary does not flow directly into a sea or ocean. Tributaries and the main stem river drain the surrounding drain ...
. As of 2018, the watershed had a population of 144,000 divided among seven incorporated cities. Aliso Creek flows over highly erosive marine
sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
of late
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...
to
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 What would become the Aliso Creek watershed originally lay at the bottom of the Pacific Ocean, before being uplifted as recently as 10 million years ago. About 1.2 million years ago, the
San Joaquin Hills The San Joaquin Hills are a low mountain range of the Peninsular Ranges System, located in coastal Orange County, California. They extend in a northwest–southeast direction, starting in the northwest in Newport Beach at the southern edge of t ...
began to uplift in the path of Aliso Creek. Occasionally swollen by wetter climates during
glacial period A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betwe ...
s, the creek carved the deep
water gap A water gap is a gap that flowing water has carved through a mountain range or mountain ridge and that still carries water today. Such gaps that no longer carry water currents are called wind gaps. Water gaps and wind gaps often offer a prac ...
known today as
Aliso Canyon Aliso Canyon is a canyon located in Orange County, California in the United States. The canyon is a water gap across the San Joaquin Hills carved out by Aliso Creek, possibly as recently as the last ice age. Located in a semi-arid climate, i ...
, the main feature of Aliso and Wood Canyons Wilderness Park. Historically, Aliso Creek served as the boundary between the
Acjachemem The Acjachemen (, alternate spelling: Acagchemem) are an Indigenous people of California. They historically lived south of what is known as Aliso Creek and north of the Las Pulgas Canyon in what are now the southern areas of Orange County and ...
(Juaneño) and
Tongva The Tongva ( ) are an Indigenous people of California from the Los Angeles Basin and the Southern Channel Islands, an area covering approximately . Some descendants of the people prefer Kizh as an endonym that, they argue, is more historically ...
(Gabrieleño) Native Americans. Spanish explorers and missionaries reached the area in the 1700s and established
Mission San Juan Capistrano Mission San Juan Capistrano ( es, Misión San Juan Capistrano) is a Spanish mission in San Juan Capistrano, Orange County, California. Founded November 1, 1776 in colonial ''Las Californias'' by Spanish Catholic missionaries of the Franciscan ...
, whose lands included part of the Aliso Creek watershed. In the 1840s the watershed was divided between several Mexican land grants. After California became part of the United States, the ranchos were gradually partitioned and sold off to farmers and settlers; starting in the 1950s, real estate companies acquired most of the land for development. By the 21st century, more than 70 percent of the Aliso Creek watershed was urbanized. Most of the creek's course has been channelized or otherwise impacted by development. Pollution and erosion from
urban runoff Urban runoff is surface runoff of rainwater, landscape irrigation, and car washing created by urbanization. Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development. During rain , storms and other precip ...
have become chronic issues. However, parts of the creek remain free flowing and provide important regional wildlife habitat, especially in the Aliso Canyon section. The creek has recently been the focus of projects to restore the stream channel and improve water quality.


Etymology

The first recorded use of the name "Aliso" was for the Rancho Cañada de los Alisos Mexican land grant in 1841. The rancho area was renamed El Toro sometime before 1900, but the name "Aliso Creek" persisted. The word ''aliso'' means "
alder Alders are trees comprising the genus ''Alnus'' in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few sp ...
" in Spanish, and refers to the riparian forests that historically occurred along the creek. The California sycamore, ''
Platanus racemosa ''Platanus racemosa'' is a species of plane tree known by several common names, including California sycamore, western sycamore, California plane tree, and in North American Spanish aliso. ''Platanus racemosa'' is native to California and Baja ...
'', is also known as ''aliso'' in Spanish, and is common in the area around the creek. According to the U.S. Geological Survey's
Geographic Names Information System The Geographic Names Information System (GNIS) is a database of name and locative information about more than two million physical and cultural features throughout the United States and its territories, Antarctica, and the associated states of ...
, the creek has also been historically called "Los Alisos Creek" and "Alisos Creek". Several nearby geographical features also share the name, including the city of Aliso Viejo, Aliso Beach, Aliso Peak (a
headland A headland, also known as a head, is a coastal landform, a point of land usually high and often with a sheer drop, that extends into a body of water. It is a type of promontory. A headland of considerable size often is called a cape.Whittow, J ...
near the creek's mouth), Los Alisos Intermediate School in
Mission Viejo Mission Viejo ( ; corruption of ''Misión Vieja'', Spanish for "Old Mission") is a commuter city in the Saddleback Valley in Orange County, California, United States. Mission Viejo is considered one of the largest master-planned communities e ...
, and Aliso Creek Road.


Course

Aliso Creek rises along the Loma Ridge in the foothills of the
Santa Ana Mountains The Santa Ana Mountains are a short peninsular mountain range along the coast of Southern California in the United States. They extend for approximately southeast of the Los Angeles Basin largely along the border between Orange and Riverside ...
, near the community of Portola Hills, Lake Forest. The creek's headwaters are at an elevation of in the
Cleveland National Forest Cleveland National Forest encompasses 460,000 acres (), mostly of chaparral, with a few riparian areas. A warm dry mediterranean climate prevails over the forest. It is the southernmost U.S. National Forest of California. It is administered by ...
near
Whiting Ranch Wilderness Park Whiting Ranch Wilderness Park is a public regional park in southern Orange County, California. Whiting Ranch features riparian, oak woodland, grassland, chaparral, and coastal sage scrub environments throughout various canyons and hillscapes. T ...
. The creek flows south along Country Home Road then begins to parallel Santiago Canyon Road, which becomes El Toro Road south of
Cook's Corner Cook's Corner is an Orange County, California bar built in 1884 that is popular with motorcyclists. It is located between the city of Lake Forest and the unincorporated community of Silverado. Cook's Corner is situated at the intersection o ...
. The creek enters
Mission Viejo Mission Viejo ( ; corruption of ''Misión Vieja'', Spanish for "Old Mission") is a commuter city in the Saddleback Valley in Orange County, California, United States. Mission Viejo is considered one of the largest master-planned communities e ...
, flowing freely in a natural streambed along the bottom of a brushy, shaded ravine. It turns southwest, crossing under the 241 toll road and passing
Saddleback Church Saddleback Church is a Baptist Evangelical multi-site megachurch, affiliated with the Southern Baptist Convention, located in Lake Forest, California. It is the largest church in California, and one of the largest in the United States of America ...
, then receives an unnamed tributary from the right. The creek then enters Lake Forest, where it receives Munger Creek from the right and English Canyon Creek from the left. Below English Canyon, Aliso Creek flows in a concrete channel through Heroes Park and then reverts to a natural channel once again in El Toro Park. Past Muirlands Boulevard the creek flows in a concrete channel, making a sharp turn to the southeast before veering back south towards
Interstate 5 Interstate 5 (I-5) is the main north–south Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels through the states of Californi ...
. Downstream of the freeway Aliso Creek flows through Laguna Hills then through Aliso Park in the retirement community of
Laguna Woods Village Laguna Woods Village is an age-restricted community for persons aged 55 and over in Laguna Woods, California. The development, formerly known as Leisure World, was developed by Ross Cortese, a former fruit stand owner turned retirement community de ...
. It enters Aliso Viejo at the Moulton Parkway bridge near Sheep Hills Park. Below this point the valley widens at the northernmost tip of Aliso and Wood Canyons Wilderness Park, the beginning of a
greenbelt A green belt is a policy and land-use zone designation used in land-use planning to retain areas of largely undeveloped, wild, or agricultural land surrounding or neighboring urban areas. Similar concepts are greenways or green wedges, which ...
that stretches from here nearly to the Pacific Ocean. Soon after entering the park, Aliso Creek is joined by the Dairy Fork from the right then the Aliso Hills Channel from the left, before passing under the 73 toll road. Below this point, the creek flows past Journey School, Aliso Niguel High School and Wood Canyon Elementary School as well as the Laguna Niguel Skate and Soccer Park, where it skirts the northwestern part of
Laguna Niguel Laguna Niguel () is a city in Orange County, California, United States. The name Laguna Niguel is derived from the words "Laguna" (Spanish for "lagoon") and "Niguili" (the name of a Native American village once located near Aliso Creek). As of ...
. Below Aliso Creek Road it is joined from the east by its largest tributary, Sulphur Creek. Sulphur Creek drains much of northern Laguna Niguel and is dammed to form
Laguna Niguel Lake Laguna Niguel Lake, formerly known as Sulphur Creek Reservoir, is an artificial fishing and recreational lake in Laguna Niguel, California. It is created by the Sulphur Creek Dam, which was completed in 1966. It is located at and is above se ...
, the main feature of
Laguna Niguel Regional Park Laguna Niguel Regional Park is a public park in Laguna Niguel, in southern Orange County, California. Its main feature is Laguna Niguel Lake (also known as Sulphur Creek Reservoir), located within the park's boundaries. Laguna Niguel's 4th of Ju ...
. From there, Aliso Creek turns west and enters Aliso Canyon, a nearly deep gorge which cuts through the
San Joaquin Hills The San Joaquin Hills are a low mountain range of the Peninsular Ranges System, located in coastal Orange County, California. They extend in a northwest–southeast direction, starting in the northwest in Newport Beach at the southern edge of t ...
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 Wood Canyon Creek is a perennial stream in Aliso and Wood Canyons Wilderness Park, Orange County, California. A tributary of Aliso Creek, it drains a deep undeveloped valley to the west of Aliso Viejo. The Wood Canyon was populated by the Acja ...
, to the south of
Soka University of America Soka University of America (SUA) is a private liberal arts college in Aliso Viejo, California. Originally founded in 1987, it was established on its current campus in 2001 by Daisaku Ikeda, the founder of the Soka Gakkai International Buddhist ...
. 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 Laguna Beach (; ''Laguna'', Spanish for "Lagoon") is a seaside resort city located in southern Orange County, California, in the United States. It is known for its mild year-round climate, scenic coves, environmental preservation efforts, and ...
. 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 The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
operated a stream gage on the creek at the El Toro Road bridge in
Mission Viejo Mission Viejo ( ; corruption of ''Misión Vieja'', Spanish for "Old Mission") is a commuter city in the Saddleback Valley in Orange County, California, United States. Mission Viejo is considered one of the largest master-planned communities e ...
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 was , with a high of in March and a low of in June. The largest flow recorded at the Laguna Beach gauge was during the
El Niño El Niño (; ; ) is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date ...
event on March 1, 1983. Urbanization is the main cause of increased winter flooding, due to the covering of land with impervious surfaces. From 1931 to 1960, the average annual peak flow at the El Toro gauge was , and between 1960 and 1980, the average peak flow was .


Watershed

The Aliso Creek
drainage basin A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
lies in the south central part of Orange County, roughly halfway between the
Santa Ana River The Santa Ana River is the largest river entirely within Southern California in the United States. It rises in the San Bernardino Mountains and flows for most of its length through San Bernardino and Riverside Counties, before cutting throug ...
and the border of
San Diego County San Diego County (), officially the County of San Diego, is a county in the southwestern corner of the U.S. state of California. As of the 2020 census, the population was 3,298,634, making it California's second-most populous county and the f ...
. It is an elongated area of , ranging from about a mile (1.6 km) in width in the north to wide in the south. The watershed is characterized by rolling hills, with very little flat land except in the alluvial valleys along Aliso Creek. The portion of the Santa Ana Mountains in the Aliso Creek watershed top out at approximately , while the San Joaquin Hills rise to at Temple Hill, locally called "Top of the World", in Laguna Beach west of Aliso Canyon. Aside from
Laguna Niguel Lake Laguna Niguel Lake, formerly known as Sulphur Creek Reservoir, is an artificial fishing and recreational lake in Laguna Niguel, California. It is created by the Sulphur Creek Dam, which was completed in 1966. It is located at and is above se ...
, an impoundment of the Sulphur Creek tributary, there are no major bodies of fresh water. The watershed experiences a dry
Mediterranean climate A Mediterranean climate (also called a dry summer temperate climate ''Cs'') is a temperate climate sub-type, generally characterized by warm, dry summers and mild, fairly wet winters; these weather conditions are typically experienced in the ...
. As of 2001, the average annual precipitation in the San Juan Hydrological Unit, which Aliso Creek is part of, was . The watershed borders five major Orange County watersheds:
Santiago Creek Santiago Creek is a major watercourse in Orange County in the U.S. state of California. About long, it drains most of the northern Santa Ana Mountains and is a tributary to the Santa Ana River. It is one of the longest watercourses entirely withi ...
to the north,
San Diego Creek San Diego Creek is a urban waterway flowing into Upper Newport Bay in Orange County, California in the United States. Its watershed covers in parts of eight cities, including Irvine, Tustin, and Costa Mesa. From its headwaters in Laguna W ...
to the west,
Laguna Canyon Laguna Canyon (also called Cañada de las Lagunas, meaning "Lake Canyon" in Spanish) is a canyon that cuts through the San Joaquin Hills in southern Orange County, California, in the United States, directly south of the city of Irvine. The ca ...
to the southwest, Salt Creek to the southeast, and San Juan Creek to the east. As of 2018, the Aliso Creek watershed had a population of 144,000 divided among seven incorporated cities, or a population density of 4,100 persons per square mile (1,600 persons per km2). Nine communities were established in the creek's watershed as it was developed in the 20th century. By 2001 seven of them had become cities (from mouth to source,
Laguna Beach Laguna Beach (; ''Laguna'', Spanish for "Lagoon") is a seaside resort city located in southern Orange County, California, in the United States. It is known for its mild year-round climate, scenic coves, environmental preservation efforts, and ...
,
Laguna Niguel Laguna Niguel () is a city in Orange County, California, United States. The name Laguna Niguel is derived from the words "Laguna" (Spanish for "lagoon") and "Niguili" (the name of a Native American village once located near Aliso Creek). As of ...
, Aliso Viejo, Laguna Hills,
Laguna Woods Laguna Woods (''Laguna'', Spanish for "Lagoon") is a city in Orange County, California, United States. The population was 16,192 at the 2010 census, down from 16,507 at the 2000 census, with a median age of 78. Laguna Woods became Orange Count ...
, Lake Forest (formerly El Toro), and
Mission Viejo Mission Viejo ( ; corruption of ''Misión Vieja'', Spanish for "Old Mission") is a commuter city in the Saddleback Valley in Orange County, California, United States. Mission Viejo is considered one of the largest master-planned communities e ...
), and the last two,
Foothill Ranch Foothill Ranch is a master planned community in Orange County, California, United States. The population was 10,899 at the 2000 census. Foothill Ranch was incorporated into the city of Lake Forest, California, in 2000. Prior to that, it was a ce ...
and Portola Hills, were incorporated into the city of Lake Forest in 2000. The largest land use in the watershed is residential, which as of 2009 accounted for 39.6 percent of the total area. Other urban land uses are commercial (10.7 percent), miscellaneous (4.9 percent), agriculture (3.7 percent) and industrial (1.6 percent). Public lands, including national forest and county parks, comprised 26.4 percent of the watershed, and another 13.1 percent was unincorporated. Much of the terrain in the watershed has been regraded to build homes and roads, and a number of smaller tributaries such as Munger Creek have been completely filled in.


Crossings

Crossings of the creek are listed from mouth to source (year built in parentheses)."South Orange Street Map- San Clemente/Mission Viejo". ''American Maps''. Langenscheidt Publishing Group, 2001. The creek is crossed by roughly 30 major bridges. * * Six footbridges in the Aliso Creek Golf Course * SOCWA Coastal Treatment Plant access road * Service Road for ACWHEP Dam * AWMA (Aliso Water Management Agency) Road * Aliso Creek Road (1988) * Pacific Park Drive * * Aliso Creek Trail * Moulton Parkway (northbound 1969, southbound 1987) * Laguna Hills Drive—twin bridges (1985) * Avenida Sevilla * Two footbridges in Aliso Park * Paseo de Valencia (1966) * Aliso Creek Trail * * Aliso Creek Trail * Los Alisos Boulevard (1973) * Muirlands Boulevard (1973) * Private road in Lake Forest Golf Center * Surf Line * Jeronimo Road (1974) * Aliso Creek Trail/2nd Street pedestrian bridge * Aliso Creek Trail * Trabuco Road—twin bridges (1975) * Creekside Drive (1980) * El Toro Road (1975) * Normandale Drive (1987) * Portola Parkway * Saddleback Parkway * * Aliso Creek Trail * Aliso Creek Trail * Glenn Ranch Road * Aliso Creek Trail * El Toro Road * El Toro Road * Santiago Canyon Road * Crystal Canyon Road * Country Home Road


Tributaries

From mouth to source, Aliso Creek is joined by seven major tributaries. Another forty-six minor streams and drains flow into the creek.


Geology

Most of
Southern California Southern California (commonly shortened to SoCal) is a geographic and cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most populous urban ...
, including all of Orange County, was part of the Pacific Ocean until about 10 million years ago (MYA) when regional uplift began. The Santa Ana Mountains, where the creek originates, began to rise about 5.5 million years ago along the Elsinore Fault. Most of the Aliso Creek watershed sits on several layers of marine sedimentary
strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as e ...
, the oldest dating from the
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...
(55.8–33.9 MYA) and the most recent, the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. ...
sediments range from in depth. The watershed includes outcrops of the Topanga Formation, Monterey Formation, San Onofre Breccia, Capistrano Formation and Niguel Formation. Generally throughout the watershed, there are five major soil and rock outcrop types—Capistrano sandy loam, Cieneba sandy loam, Marina loamy sand, Myford sandy loam, and Cieneba-rock outcrop. The
water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...
ranges from deep. About 1.22 million years ago, the
San Joaquin Hills The San Joaquin Hills are a low mountain range of the Peninsular Ranges System, located in coastal Orange County, California. They extend in a northwest–southeast direction, starting in the northwest in Newport Beach at the southern edge of t ...
along the Orange County coast began their uplift along the San Joaquin Hills blind
thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...
which extends south from the
Los Angeles Basin The Los Angeles Basin is a sedimentary basin located in Southern California, in a region known as the Peninsular Ranges. The basin is also connected to an anomalous group of east-west trending chains of mountains collectively known as the ...
. The hills rose directly in the path of Aliso Creek, which cut a
water gap A water gap is a gap that flowing water has carved through a mountain range or mountain ridge and that still carries water today. Such gaps that no longer carry water currents are called wind gaps. Water gaps and wind gaps often offer a prac ...
through the range, forming
Aliso Canyon Aliso Canyon is a canyon located in Orange County, California in the United States. The canyon is a water gap across the San Joaquin Hills carved out by Aliso Creek, possibly as recently as the last ice age. Located in a semi-arid climate, i ...
. The uplift also diverted Sulphur Creek, which originally flowed south into Salt Creek, to turn north and join Aliso Creek. During the last glacial period (110,000 to 10,000 years ago), especially in the
Wisconsinian glaciation The Wisconsin Glacial Episode, also called the Wisconsin glaciation, was the most recent glacial period of the North American ice sheet complex. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cord ...
(31,000 to 10,000 years ago), the climate of Southern California became periodically much wetter, with a climate similar to the present-day
Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Thou ...
. At these times Aliso Creek was a river carrying much more water than it does today. During glacial periods sea level was as much as lower, increasing the stream gradient and thus its erosive force. These factors led to Aliso Creek carving out a much larger series of valleys than would appear possible with its present-day volume. As sea levels rose after the Wisconsinian glaciation, Aliso Canyon became a long narrow bay. Over thousands of years Aliso Creek filled in the bay with sediment, creating the flat alluvial valley floor seen today, while the creek itself remains as an underfit stream.


Ecology


Plants

Before urbanization of the watershed, Aliso Creek and some of its tributaries supported a significant
riparian zone A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks a ...
dominated by native hardwoods such as
coast live oak ''Quercus agrifolia'', the California live oak, or coast live oak, is a highly variable, often evergreen oak tree, a type of live oak, native to the California Floristic Province. It may be shrubby, depending on age and growing location, but is ...
,
sycamore Sycamore is a name which has been applied to several types of trees, but with somewhat similar leaf forms. The name derives from the ancient Greek ' (''sūkomoros'') meaning "fig-mulberry". Species of trees known as sycamore: * ''Acer pseudoplata ...
,
alder Alders are trees comprising the genus ''Alnus'' in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few sp ...
, cottonwood and arroyo willow. Many of the trees in Aliso Creek's riparian zone, especially near the mouth of the creek, were cut down in the Spanish Mission period to construct colonial settlements. During the early 20th century, groundwater withdrawal for agriculture killed off many of the remaining trees along the creek. The most significant remaining riparian habitat today occurs in Aliso and Wood Canyons, and along the uppermost headwaters of Aliso Creek. Increased erosion and pollution caused by urban runoff have had adverse impacts on the riparian zone. Invasive plants, including tobacco tree,
castor bean ''Ricinus communis'', the castor bean or castor oil plant, is a species of perennial flowering plant in the spurge family, Euphorbiaceae. It is the sole species in the monotypic genus, ''Ricinus'', and subtribe, Ricininae. The evolution of ...
,
pampas grass Pampas grass or pampas-grass is a common name which may refer to any of several similar-looking, tall-growing species of grass: * Species of '' Cortaderia'' including: :* ''Cortaderia selloana'' and its selected cultivars :* ''Cortaderia jubata'' ( ...
, periwinkle, and artichoke thistle, but most notably the giant reed, have in many places replaced native trees. Giant reed was originally planted in the 1970s to control erosion. These invasive species are most prevalent along upper Sulphur Creek, the lower half of Aliso Creek, and Wood Canyon Creek. The hilly terrain of the watershed supports mostly grassland and coastal scrub vegetation. Native shrub species present in the watershed include California brittlebush,
California buckwheat ''Eriogonum fasciculatum'' is a species of wild buckwheat known by the common names California buckwheat and flat-topped buckwheat. Characterized by small, white and pink flower clusters that give off a cottony effect, this species grows vari ...
, California sagebrush, California goldenbush, coyote brush and mule fat. Like the riparian zones, native grassland and shrublands have been heavily impacted by invasive species. A 2009 survey conducted in the Aliso Creek watershed found non-native grass coverage of between 66 and 100 percent, and non-native shrub coverage of between 0 and 50 percent, across fourteen sample sites. Although most of the creek channel is tightly bound by urban development, it is considered a potential
wildlife corridor A wildlife corridor, habitat corridor, or green corridor is an area of habitat connecting wildlife populations separated by human activities or structures (such as roads, development, or logging). This allows an exchange of individuals between ...
between these two areas. The U.S. Army Corps of Engineers describes the corridor as "meager at best with several places where Aliso Creek is very narrow, concrete, or incorporates golf courses parks and school grounds." The watershed supports multiple native bird species, including California least tern,
least Bell's vireo Bell's vireo (''Vireo bellii'') is a songbird that migrates between a breeding range in Western North America and a winter range in Central America. It is dull olive-gray above and whitish below. It has a faint white eye ring and faint wing bars ...
, southwestern willow flycatcher,
California gnatcatcher The California gnatcatcher (''Polioptila californica'') is a small long insectivorous bird which frequents dense coastal sage scrub growth. This species was recently split from the similar black-tailed gnatcatcher of the Sonoran and Chihuahuan ...
, and western snowy plover. The loss of riparian zones has reduced bird habitat in the watershed. These species are mostly found in undeveloped areas of Aliso and Wood Canyons, the upper reaches of Aliso Creek, and some parts of English Canyon Creek. Aliso Canyon is one of the most diverse bird habitats in Orange County, with some 122 nesting and migratory species found there. The canyon also has raptors including
northern harrier The northern harrier (''Circus hudsonius''), or ring-tailed hawk, is a bird of prey. It breeds throughout the northern parts of the northern hemisphere in Canada and the northernmost USA. The northern harrier migrates to more southerly areas ...
,
Cooper's hawk Cooper's hawk (''Accipiter cooperii'') is a medium-sized hawk native to the North American continent and found from southern Canada to Mexico. This species is a member of the genus ''Accipiter'', sometimes referred to as true hawks, which are f ...
,
golden eagle The golden eagle (''Aquila chrysaetos'') is a bird of prey living in the Northern Hemisphere. It is the most widely distributed species of eagle. Like all eagles, it belongs to the family Accipitridae. They are one of the best-known bird ...
and
peregrine falcon The peregrine falcon (''Falco peregrinus''), also known as the peregrine, and historically as the duck hawk in North America, is a cosmopolitan bird of prey (raptor) in the family Falconidae. A large, crow-sized falcon, it has a blue-grey bac ...
.
, orange-throated whiptail, coastal western whiptail,
coast horned lizard The coast horned lizard (''Phrynosoma coronatum'') is a species of phrynosomatid lizard endemic to Baja California Sur in Mexico. As a defense the lizard can shoot high pressure streams of blood out of its eyes if threatened. Taxonomy It was ...
, California legless lizard, and two-striped garter snake.
s have been introduced to parts of the creek. The threatened south
western pond turtle The Western pond turtle (''Actinemys marmorata''), also known commonly as the Pacific pond turtle is a species of small to medium-sized turtle in the family Emydidae. The species is endemic to the western coast of the United States and Mexico, r ...
, the only indigenous turtle species to Orange County, is also found in the creek.Arkive The ...
, which can tolerate the low oxygen levels and high temperatures typical of the creek water. Aside from carp, several other native and introduced fish species were found in the creek until the 1980s, including
mosquito fish The western Mosquitofish (''Gambusia affinis'') is a North American freshwater fish, also known commonly, if ambiguously, as simply Mosquitofish or by its generic name, ''Gambusia'', or by the common name gambezi. Its sister species, the easte ...
,
bluegill The bluegill (''Lepomis macrochirus''), sometimes referred to as "bream", "brim", "sunny", or "copper nose" as is common in Texas, is a species of North American freshwater fish, native to and commonly found in streams, rivers, lakes, ponds an ...
,
bass Bass or Basses may refer to: Fish * Bass (fish), various saltwater and freshwater species Music * Bass (sound), describing low-frequency sound or one of several instruments in the bass range: ** Bass (instrument), including: ** Acoustic bass gui ...
, and
channel catfish The channel catfish (''Ictalurus punctatus'') is North America's most numerous catfish species. It is the official fish of Kansas, Missouri, Iowa, Nebraska, and Tennessee, and is informally referred to as a "channel cat". In the United States, the ...
. After flooding exacerbated by urban runoff destroyed much of the remaining riparian habitat, these species were reported to have disappeared from the area. The historical presence of endangered
steelhead trout Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout or redband trout (O. m. gairdneri). Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and ...
(''Oncorhynchus mykiss'') in Aliso Creek has been debated. Until 2006 the
National Marine Fisheries Service The National Marine Fisheries Service (NMFS), informally known as NOAA Fisheries, is a United States federal agency within the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) that is responsible for the stew ...
(NMFS) stated that there was "no evidence of historical or extant of ''O. mykiss'' in anadromous waters" in Aliso Creek. However, a 1998 study co-authored by the U.S. Army Corps of Engineers and US Fish & Wildlife Service declared that steelhead had inhabited the creek until the 1970s, when increased urbanization resulted in poor water quality conditions (pollution and low oxygen levels) that drove the migrational fish out. In 2009, after years of petitioning from local residents and environmental groups including Friends of the Aliso Creek Steelhead and Clean Water Now, the NMFS recognized the lower of Aliso Creek as former steelhead habitat and the creek was added to the Distinct Population Segment List under the jurisdictional domain of NOAA.National Marine Fisheries Service. ''Technical Memorandum #394 Steelhead of the South-Central/Southern California Coast: Population Characterization for Recovery Planning'' (2006). It is now considered a candidate for re-colonization. The evidence cited included Native American (Acjachemen) accounts of takings, as well as anglers who reported taking steelhead trout in the 1960s and 1970s from Aliso Creek's estuary and Aliso Canyon before suburban development began. The last reported observation of steelhead in Aliso Creek was in 1972. In the 1970s, a large population of the threatened
tidewater goby ''Eucyclogobius newberryi'', the Northern tidewater goby, is a species of goby native to lagoons of streams, Marsh, marshes, and creeks along the coast of California, United States. The Northern tidewater goby is one of six native goby species to ...
(10,000–15,000) was documented in the Aliso Creek estuary. The species has declined significantly since then due to pollution and reduction of its habitat. In 2011 the U.S. Fish and Wildlife Service designated the Aliso Creek estuary and several other coastal Southern California streams as critical habitat for the tidewater goby.


History


First inhabitants

Aliso Creek historically served as a boundary between the
Tongva The Tongva ( ) are an Indigenous people of California from the Los Angeles Basin and the Southern Channel Islands, an area covering approximately . Some descendants of the people prefer Kizh as an endonym that, they argue, is more historically ...
Native Americans in the north, and the
Acjachemen The Acjachemen (, alternate spelling: Acagchemem) are an Indigenous people of California. They historically lived south of what is known as Aliso Creek and north of the Las Pulgas Canyon in what are now the southern areas of Orange County and ...
(sometimes grouped with the larger Payómkawichum) in the south. The Tongva's territory extended north, past the
Santa Ana River The Santa Ana River is the largest river entirely within Southern California in the United States. It rises in the San Bernardino Mountains and flows for most of its length through San Bernardino and Riverside Counties, before cutting throug ...
and San Gabriel River, into present-day
Los Angeles County Los Angeles County, officially the County of Los Angeles, and sometimes abbreviated as L.A. County, is the List of the most populous counties in the United States, most populous county in the United States and in the U.S. state of California, ...
, while the Acjachemen's smaller territory extended from Aliso Creek south, past San Juan Creek, and to the vicinity of San Mateo Creek in present-day
San Diego County San Diego County (), officially the County of San Diego, is a county in the southwestern corner of the U.S. state of California. As of the 2020 census, the population was 3,298,634, making it California's second-most populous county and the f ...
. The availability of perennial water in some parts of the creek made it an attractive location for Native Americans to camp, hunt, gather and fish. The numerous oak groves along the creek provided an abundant supply of acorns, a staple of their diet. About 70 archaeological sites have been discovered along the creek, with 33 on the northwest side and 47 on the southeast side. An Acjachemen village situated near the confluence of Aliso Creek and Sulphur Creek was named Niguili, possibly meaning "a large spring" in the
Luiseño language The Luiseño language is a Uto-Aztecan language of California spoken by the Luiseño, a Native American people who at the time of first contact with the Spanish in the 16th century inhabited the coastal area of southern California, ranging fr ...
. The placement of the tribal boundary at Aliso Creek has been disputed, as the usual practice among indigenous peoples of this region was to claim watershed divides rather than stream channels as boundaries. Constance Cameron challenged this view in the paper ''Aliso Creek: The Great Divide?'' (1974) presented to the Southern California Academy of Sciences, arguing that the boundary lay north of Aliso Creek and that the entire stream lay within Acjachemen land. D. Earle (1992) further stated that "There is some evidence... that Gabrielino (Tongva) territory may have extended only as far south as the Tustin Plain" (a location about north of Aliso Creek). This contradicts the generally accepted theory originated by Alfred L. Kroeber (1925) who stated that "Juaneño (Acjachemen) place names do not extend north of Aliso Creek". ''The Master Key'' (1956) by Bernice Eastman Johnson and ''The First Angelinos'' (1996) by W. McCawley also place the boundary at Aliso Creek.


Spanish exploration and colonization

On July 24, 1769, the Spanish Portolà expedition led by
Gaspar de Portolá Gaspar de Portolá y Rovira (January 1, 1716 – October 10, 1786) was a Spanish military officer, best known for leading the Portolá expedition into California and for serving as the first Governor of the Californias. His expedition laid t ...
, traveling north from San Diego, reached a stream which Fray Joan Crespí described as "Alisos Creek", which was actually the
Arroyo Trabuco Arroyo Trabuco (known also as Trabuco Creek) is a -long stream in coastal southern California in the United States. Rising in a rugged canyon in the Santa Ana Mountains of Orange County, the creek flows west and southwest before emptying into S ...
. They camped there for two days before continuing on and crossing what is now known as Aliso Creek, where they found wild grapes and roses in abundance, on July 26. Crespí wrote in his diary, "So we went on over very open country, with hills and broad mesas, ascending and descending through three or four little valleys of good soil well grown with alders." He also wrote of the local Acjachemen people: "They came without arms and with a friendliness unequaled; they made us presents of their poor seeds and we made return with ribbons and gew-gaws." These first explorers were soon followed by Franciscan missionaries who established
Mission San Juan Capistrano Mission San Juan Capistrano ( es, Misión San Juan Capistrano) is a Spanish mission in San Juan Capistrano, Orange County, California. Founded November 1, 1776 in colonial ''Las Californias'' by Spanish Catholic missionaries of the Franciscan ...
in 1776 near the main population center of the Acjachemen people, on San Juan Creek about east of the mouth of Aliso Creek. The Spanish referred to the Acjachemen as the Juaneño, and to the Tongva as the Gabrielino, after the further away
Mission San Gabriel Arcángel Mission San Gabriel Arcángel ( es, Misión de San Gabriel Arcángel) is a Californian mission and historic landmark in San Gabriel, California. It was founded by Spaniards of the Franciscan order on "The Feast of the Birth of Mary," September ...
. The Aliso Creek watershed was part of the vast land holdings of Mission San Juan Capistrano. The El Camino Real ("King's Highway"), connecting the coastal missions in California, crossed Aliso Creek in the vicinity of El Toro (today's Lake Forest). The Spanish established Rancheria Niguel in what is now the city of Aliso Viejo and grazed their cattle there. Most of the Native Americans were relocated to the mission where they were forced into agricultural labor and converted to Spanish Catholicism. In order to provide timber for Spanish settlements, most of the riparian forests around Aliso Creek were heavily logged. It was said that the trees near the mouth of Aliso Canyon were especially tall and there were accounts of Spanish ships mooring in the large bay at the outlet of Aliso Canyon and men going ashore to chop down and take away these trees for constructing mission buildings, ships and other structures.


Mexican land grants

Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
won independence from Spain in 1822, keeping the
Alta California Alta California ('Upper California'), also known as ('New California') among other names, was a province of New Spain, formally established in 1804. Along with the Baja California peninsula, it had previously comprised the province of , but ...
province, and secularized the missions in the 1830s. Former mission lands were divided into private land grants. In 1842, Don Juan Avila received the
Rancho Niguel Rancho Niguel was a Mexican land grant in the San Joaquin Hills, within present-day Orange County, California. It was granted in 1842 by Governor Juan B. Alvarado to Juan Avila. The rancho was named for a local Indian village called "Niguili." ...
grant. The name of the rancho was derived from the original Rancheria Niguel, which in turn received its name from the Acjachemen village that once stood nearby. Rancho Niguel included the portion of the Aliso Creek watershed stretching from what is now I-5 nearly to the Pacific, as well as significant areas of land on either side. Don Juan became known as "El Rico" for his wealth and hospitality; he made a fortune driving beef cattle up to Northern California after the
gold rush A gold rush or gold fever is a discovery of gold—sometimes accompanied by other precious metals and rare-earth minerals—that brings an onrush of miners seeking their fortune. Major gold rushes took place in the 19th century in Australia, New ...
started in 1848. "The hospitality of the Avila’s were legendary. In 1846 and 1847 Generals Frémont and Kearny as well as Commodore Stockton were said to have been entertained. General Andreas Pico and the last two Mexican governors
Pío Pico Don Pío de Jesús Pico (May 5, 1801 – September 11, 1894) was a Californio politician, ranchero, and entrepreneur, famous for serving as the last governor of California (present-day U.S. state of California) under Mexican rule. A member of t ...
and
José María Flores General José María Flores was a Captain in the Mexican Army and was a member of ''la otra banda''. He was appointed Governor and ''Comandante General'' ''pro tem'' of Alta California from November 1846 to January 1847, and defended California ...
were also welcome visitors... There was always music and plenty of food. Whenever provisions ran low, locals knew that they could always count of the generosity of Don Juan." Rancho Cañada de los Alisos (translated as "Valley of the Alders" or "Valley of the Sycamores"), encompassing the northern half of the Aliso Creek watershed including what would become El Toro, was granted to Don José Antonio Fernando Serrano (Don Juan's brother-in-law) in 1842–1846. The nearly rancho would come to feature large tracts of grazing land as well as vineyards, orchards and vegetable gardens near Aliso Creek. El Camino Real provided the boundary between the two ranchos; Don José and Don Juan built adobes along Aliso Creek on either side of the road (though Don Juan's main residence was in San Juan Capistrano). Don José also had a racetrack and rodeo grounds near Aliso Creek, near the present day intersection of El Toro Road and Muirlands Blvd. The foundation of the Avila adobe still exists today, south of I-5 with a sign marking its location. There is no trace today of the original Serrano residence, although its precise location has been identified in Sycamore Park in Mission Viejo, on the east bank of Aliso Creek north of I-5. In 1996 descendants of the Serrano and Avila families and others dedicated a plaque at the site.


Statehood

Following the
Mexican–American War The Mexican–American War, also known in the United States as the Mexican War and in Mexico as the (''United States intervention in Mexico''), was an armed conflict between the United States and Mexico from 1846 to 1848. It followed the ...
, California was annexed by the United States, becoming the 31st state in 1850. In 1871, the first American settler along Aliso Creek, Eugene Salter, claimed near the mouth of the creek inside Aliso Canyon, but abandoned it soon after. The following year the land was acquired by homesteaders George and Sarah Thurston and their eight children, who converted the land surrounding the creek into orchards and vegetable gardens, and later helped establish a public campground at Aliso Beach. In 1914 most of the Thurston family left for Santa Ana, though their son Joe stayed until selling the land in 1921. It served as a Girl Scout camp for several years before the Laguna Beach Country Club, the precursor of the present day hotel and golf course, was built in 1950. After the severe drought of 1863–64, in which thousands of cattle died, Don José Serrano was forced to sell the Rancho Cañada de los Alisos to J.S. Slauson, a Los Angeles banker. The ranch passed through several owners before being acquired by Dwight Whiting in 1884. Whiting heavily promoted the settlement of the area, calling it "Aliso City". The name "El Toro" (of unclear origin, though it had been in use since 1838) was used after the U.S. Postal Service declined the name "Aliso" for a post office, citing that it was too similar to Alviso. He granted a right of way to the California Southern Railroad Company and even traveled to England to "encourage 'gentleman farmers' to come to El Toro to raise oranges and walnuts." The Surf Line was extended through the area in 1888, connecting Los Angeles to San Diego via Orange County. By 1932,
citrus ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is native to ...
and other fruit trees were the main crops in El Toro, irrigated by wells sunk into the shallow groundwater basins along Aliso creek. For similar reasons, Don Juan Avila sold the Rancho Niguel in 1865 to John Forster, and the property was eventually purchased by Lewis Moulton and Jean Pierre Daguerre in 1895. Daguerre was one of many
Basque Basque may refer to: * Basques, an ethnic group of Spain and France * Basque language, their language Places * Basque Country (greater region), the homeland of the Basque people with parts in both Spain and France * Basque Country (autonomous co ...
immigrants who arrived in this part of Orange County starting in the 1870s, introducing sheep ranching and crops of bean and barley to the area. Moulton and Daguerre purchased parts of adjoining ranches, bringing the total size of the property to . The ranch remained under their ownership for approximately thirty-eight years, and the Moulton family continued to own it until the 1960s. Cattle and sheep ranching and dryland farming continued on Rancho Niguel until the mid-20th century.


Urbanization and development

In 1927
Laguna Beach Laguna Beach (; ''Laguna'', Spanish for "Lagoon") is a seaside resort city located in southern Orange County, California, in the United States. It is known for its mild year-round climate, scenic coves, environmental preservation efforts, and ...
became the first city to be incorporated in the Aliso Creek watershed and the second in Orange County. Wells were drilled into the stream bed near its mouth and water was piped to homes in Laguna Beach. However, in 1928 the Aliso Creek supply was discontinued due to "the undesirable quality of the water" caused by high
chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride s ...
levels. The idea of using uncontaminated surface water from Aliso Creek was also considered, but this would require the construction of a large storage reservoir. In 1934, an A. J. Stead proposed to build a dam just above the mouth of the creek to store and provide a firm annual yield of of water. Lewis Moulton filed a lawsuit as the reservoir would flood part of the Rancho Niguel, but the dam project was upheld in a hearing in 1936. However, this dam was never built. With the exception of the farming community of El Toro, the rest of the watershed remained largely unpopulated into the 1950s. In the 1950s, Rancho Niguel was sold off to real estate developers to build the planned cities of Laguna Niguel, Aliso Viejo, and Laguna Hills, with an undeveloped portion to the south that would later become Aliso and Wood Canyons Wilderness Park. Up until the 1960s and 1970s, barely 15 percent of the watershed was urbanized, but by 1990, after doubling the rate of development in the past two decades, the watershed was roughly 60 percent urbanized. The cities of Mission Viejo and Laguna Niguel were incorporated in 1988 and 1989, respectively. In 1991 El Toro incorporated as the city of Lake Forest; Laguna Hills also incorporated in 1991, and Laguna Woods in 1999. By the early 21st century, more than 70 percent of the watershed was urbanized. The newest city in the watershed, Aliso Viejo, was incorporated in 2001.


Flood control

In the early 1900s, several significant floods wreaked havoc in southern California. The Orange County Flood Control District was created by Orange County Flood Control Act of 1927 in response to some of these flooding events. Over the following decades most streams in Orange County were channelized, with Aliso Creek being channelized to facilitate urban development starting in the 1960s. Although some parts of Aliso Creek were completely lined with concrete, it retains an earthen riverbed in most parts despite being confined to a narrow channel. A major weakness in the flood control system is at the south end of Aliso Canyon where the creek is confined by steep cliffs and the Aliso Creek golf course. This area has suffered severe flood damage several times in the 20th century. The 1998 flood was the largest on record. It inundated the Aliso Creek Inn and Golf Course, destroyed six footbridges across Aliso Creek and caused severe bank erosion in many places along the creek. Like most other coastal Orange County streams, the watershed of Aliso Creek is now heavily urbanized. With 70 percent of the original land surface now underneath impermeable surfaces such as pavement and buildings, far more runoff now enters the creek during storm events, greatly increasing the risk of flooding. Several tributaries of Aliso Creek—the Dairy Fork, Aliso Hills Channel, Munger Creek, and other smaller ones—have been replaced by storm drains. Parts of Sulphur Creek and English Canyon Creek have been channelized as well. The only tributary that closely resembles its natural condition is Wood Canyon Creek, although it is still affected considerably by urban runoff. There are several facilities capable of storing floodwaters, the largest of which is Laguna Niguel Lake formed by the Sulphur Creek Dam on Sulphur Creek. The Sulphur Creek Dam, completed in 1966, was built as an irrigation reservoir, but was acquired by the Orange County Flood Control District in 1970. In addition, there are two detention basins on the main stem of Aliso Creek. The first is El Toro Detention Basin, an off-stream basin in a portion of Heroes Park in Lake Forest, and the second is the on-stream Pacific Park Detention Basin in Aliso Viejo. There are also detention basins constructed on upper Wood Canyon Creek, Dairy Fork, and English Canyon Creek. Nineteen
drop structure A drop structure, also known as a grade control, sill, or weir, is a manmade structure, typically small and built on minor streams, or as part of a dam's spillway, to pass water to a lower elevation while controlling the energy and velocity of the ...
s have been constructed on Aliso Creek to mitigate the damaging erosion caused by increased flooding. Many of these structures were constructed in response to a 1969 flood that caused $1 million of damage along Aliso Creek, while others were necessary to mitigate erosion caused by artificial straightening of the stream channel. In one of the largest such projects, at Aliso Creek Road, the creek was realigned in an excavated channel through a ridge in order to accommodate the construction of the
Chet Holifield Federal Building The Chet Holifield Federal Building, colloquially known as "the Ziggurat Building", is a United States government building in Laguna Niguel, California. It was built between 1968 and 1971 for North American Aviation/Rockwell International, and de ...
and Alicia Parkway. Because this shortened the stream channel by about and increased its gradient, two drop structures were constructed to prevent the creek from eroding upstream.


Environmental issues

Aliso Creek is listed as a
Clean Water Act The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the responsibiliti ...
impaired water, which is defined by the
U.S. Environmental Protection Agency The Environmental Protection Agency (EPA) is an Independent agencies of the United States government, independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon pro ...
as "impaired by one or more pollutants that do not meet one or more water quality standards". The creek frequently exceeds bacterial limits set by California law. At Aliso Beach, the creek water is considered unsafe for swimming 99 percent of the time. Contact with seawater at the beach is discouraged for 72 hours (3 days) after a major storm event. The creek contains elevated levels of E. coli, phosphorus, nitrogen and selenium, which comes mainly from heavy application of fertilizer and manure, and other organic pollutants in urban runoff. High water temperatures, sometimes exceeding in the summer, promote the growth of bacteria as well as algae blooms leading to
eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phyt ...
. Runoff of chlorine, oils and heavy metals, mainly caused by irrigation and car washing, have killed off most fish and shrimp species in the creek, with the exception of carp. The ''
Los Angeles Times The ''Los Angeles Times'' (abbreviated as ''LA Times'') is a daily newspaper that started publishing in Los Angeles in 1881. Based in the LA-adjacent suburb of El Segundo since 2018, it is the sixth-largest newspaper by circulation in the ...
'' reported in 1997 that "County health officials acknowledge that the bacterial count at the mouth of the creek—which curls into a warm-water stagnant pond that flushes out onto the beach—is at times alarmingly high, often surpassing the legal limit for California. As a result, the area where the creek meets the sea, and the creek itself, are considered permanently off limits to swimmers and bear prominent signs that warn of the dangers of trespassing into such toxic waters. Nevertheless, people do, almost daily. Officials from the Orange County Environmental Health Department say that
skin rash A rash is a change of the human skin which affects its color, appearance, or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cr ...
es, infections, " pink eye" and other assorted ailments are not uncommon to those who use Aliso Beach and, unwittingly, come in contact with the creek and its invisible bacteria...". Urbanization has also changed sediment transport in the creek. The obstruction of natural sediment sources and increased water flow due to urban runoff has caused significant downcutting in the river bed. The creek has eroded to depths exceeding below its original bed in some areas, disconnecting the creek from its natural
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
and riparian zones. In 2017 the U.S. Army Corps of Engineers reported that $5 million of damage had been caused by erosion along lower Aliso Creek. This includes physical damage to creek banks, bridges, roads and water pipelines. Landslides have occurred along the creek and its tributaries, including at English Canyon in the 1990s. The creek is estimated to deliver 20,000–60,000 tons of sediment to the sea in an average year, and as much as 200,000 tons in wet years. The South Orange County Wastewater Authority (SOCWA) Coastal Treatment Plant is located next to Aliso Creek in Laguna Beach, and treats about 2.9 million gallons (11 million litres) of sewage each day. Treated wastewater is discharged into the Pacific Ocean about offshore from Aliso Beach via the Aliso Creek Ocean Outfall. A pipeline carrying raw sewage downstream to the treatment plant and two pipelines carrying treated sludge back upstream to SOCWA's Regional Treatment Plant in Laguna Niguel for recycling are buried roughly parallel to the creek within Aliso Canyon, and have been frequently threatened by flooding and erosion. Sewage spills have occasionally entered the creek, forcing the closure of Aliso Beach. In 2016, the
California Coastal Commission The California Coastal Commission (CCC) is a state agency within the California Natural Resources Agency with quasi-judicial control of land and public access along the state's coastline. Its mission as defined in the California Coastal Act is ...
approved a project to replace the two treated sludge lines, which had deteriorated extensively over the last 30 years.


Restoration projects

There have been several attempts to clean up the creek, stabilize its banks and restore native habitat. One of the earlier projects was Aliso Creek Wildlife Habitat Enhancement Project (ACWHEP), conceived and jointly funded by the County of Orange and the Mission Viejo Company, and intended to rehabilitate of former riparian areas that were dried up due to downcutting of the stream channel. A high concrete dam was built about downstream of Aliso Creek Road, inside Aliso Canyon, to increase the water level so that the riparian area could be restored. Due to poor design as well as storm damage from 1998 flooding, the dam ended up causing further erosion of the creek downstream due to the rapid flow of water cascading over the structure, and the project was abandoned. The dam is now considered a failure risk and must be periodically grouted to maintain its stability. In 2006 the U.S. Army Corps of Engineers began studies for the Aliso Creek Mainstem Ecosystem Restoration Project, which aims to control erosion and restore riparian habitat along the lower of the creek downstream of Pacific Park Drive, as well as short stretches of lower Wood Canyon and Sulphur Creeks. The project would remove the existing drop structures and barriers along this section of the creek and construct 47 low rock riffles to maintain a constant gradient. Parts of the creek prone to erosion would be realigned to slow down the water velocity, and the creek banks in several places would be stabilized with buried concrete walls. A total of of riparian areas would be reconnected to the creek's floodplain. All non-native plant species would be removed. As of 2017 this project had an estimated cost of $91 to $99 million. The USACE project has been criticized for its potential large impacts on Aliso and Wood Canyons Wilderness Park as it would require extensive re-grading of the stream channel and banks, with of excavations and more than of fill. In addition, many of the proposed structures are intended to protect the sewer lines along Aliso Creek in Aliso Canyon, rather than for environmental restoration. The
Sierra Club The Sierra Club is an environmental organization with chapters in all 50 United States, Washington D.C., and Puerto Rico. The club was founded on May 28, 1892, in San Francisco, California, by Scottish-American preservationist John Muir, who b ...
has advocated for the closure of the Coastal Treatment Plant in Aliso Canyon, and for wastewater to be recycled or treated at the nearby J.B. Latham plant instead, which would significantly reduce the cost of the Aliso Creek restoration project and reduce its environmental impacts. As of 2016, the Latham plant was operating at about 50 percent of its capacity. A number of artificial wetlands have been constructed in the Aliso Creek watershed to replace historic wetlands lost to urban development. The Wood Canyon Emergent Wetland was constructed in 2005 at the head of Wood Canyon Creek in Aliso Viejo, and consists of a series of retaining ponds that slow down stormwater and support the growth of riparian vegetation. In June 2017 the Dairy Fork Wetland and Habitat Restoration Project, also in Aliso Viejo, was completed at a cost of $1.3 million. The project was designed to collect and treat urban runoff from the Dairy Fork tributary basin. Water flows into a series of pools where it is filtered by vegetation and bacteria are killed by prolonged exposure to sunlight, before entering of restored riparian habitat along Aliso Creek. This was expected to reduce dry season pollutants by as much as 99 percent. In October 2017 the Laguna Ocean Foundation presented a concept restoration plan for the Aliso Creek estuary, which was endorsed by Orange County Supervisor Lisa Bartlett and Senator
Patricia Bates Patricia "Pat" Carmody Bates (born December 15, 1939) is an American Republican politician currently serving in the California State Senate, representing the 36th Senate district, which encompasses parts of Orange and San Diego counties. She ...
(R-Laguna Niguel). The project would remove a parking lot and artificial turf on the north side of Highway 1 in order to restore the estuary to its original size. The estuary restoration also depends on reducing the dry weather flow in Aliso Creek, which would be accomplished by diverting a portion of the creek's flow at the Coastal Treatment Plant and feeding it into the existing recycled water system. This would lower the frequency with which water breaches the sandbar separating the estuary from the Pacific Ocean, enhancing habitat stability for species such as the tidewater goby and western pond turtle. In 2018, the sandbar was not breached over the summer for the first time in ten years.


Parks and preservation

The
Cleveland National Forest Cleveland National Forest encompasses 460,000 acres (), mostly of chaparral, with a few riparian areas. A warm dry mediterranean climate prevails over the forest. It is the southernmost U.S. National Forest of California. It is administered by ...
is the oldest public land in the Aliso Creek watershed, although it only encompasses a very small portion of the headwaters. The upper Aliso Creek originally became part of the Trabuco Cañon Forest Reserve – one of the first established after the Forest Reserve Act of 1891 – in 1893, before President
Theodore Roosevelt Theodore Roosevelt Jr. ( ; October 27, 1858 – January 6, 1919), often referred to as Teddy or by his initials, T. R., was an American politician, statesman, soldier, conservationist, naturalist, historian, and writer who served as the 26t ...
formally established the Cleveland National Forest in 1908. Whiting Ranch Wilderness Park, which also contains a small portion of the Aliso Creek headwaters, was set aside in the early 1900s on land donated by Dwight Whiting from the Rancho Cañada de los Alisos. At the other end of the creek, Aliso Beach has been used as a recreation area since the early 20th century, when the Thurston family created the Aliso Canyon Wagon Trail and established a campground at the beach. The County of Orange began to manage the beach in 1949. A unique diamond shaped pier was constructed in 1970, but after damage caused by the 1998 storm it was permanently removed. Today, Aliso is one of the county's most popular beaches with over one million annual visitors. During the mid-20th century, certain tracts of land were set aside in the Aliso Creek watershed to preserve wildlife habitat and a partial greenway along the creek itself. Significant amounts of open space were also dedicated in many of the master planned communities developed along the creek. More than 35 percent of Laguna Niguel was designated as parks and open space in its master plan, as was 20 percent of Mission Viejo. The
Laguna Niguel Regional Park Laguna Niguel Regional Park is a public park in Laguna Niguel, in southern Orange County, California. Its main feature is Laguna Niguel Lake (also known as Sulphur Creek Reservoir), located within the park's boundaries. Laguna Niguel's 4th of Ju ...
, which surrounds Laguna Niguel Lake and part of Sulphur Creek, was created in 1973. Laguna Niguel Lake is regularly stocked with
catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...
,
bass Bass or Basses may refer to: Fish * Bass (fish), various saltwater and freshwater species Music * Bass (sound), describing low-frequency sound or one of several instruments in the bass range: ** Bass (instrument), including: ** Acoustic bass gui ...
,
bluegill The bluegill (''Lepomis macrochirus''), sometimes referred to as "bream", "brim", "sunny", or "copper nose" as is common in Texas, is a species of North American freshwater fish, native to and commonly found in streams, rivers, lakes, ponds an ...
, and
trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', '' Salmo'' and '' Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salm ...
during the winter months, and offers both shoreline fishing and boat rentals. The future of Aliso Canyon remained uncertain into the 1970s. As part of the original development plans for the former Rancho Niguel, a six-lane highway was planned for the length of Aliso Canyon, connecting inland cities with Laguna Beach. This would have sliced directly through what is now Aliso and Wood Canyons Wilderness Park and heavily impacted the only significant remaining natural stretch of Aliso Creek. Land for the wilderness park was first secured in April 1979 with , and small increments were added to the park until the early 1990s forming a total of . In the 1990s, Aliso and Wood Canyons became part of the South Coast Wilderness Area, a group of preserves which includes the Laguna Coast Wilderness Park and
Crystal Cove State Park Crystal Cove State Park is a state park of California, United States, encompassing of Pacific coastline, inland chaparral canyons, and the Crystal Cove Historic District of beach houses. The park is located in Newport Beach, and is part of the ...
. In 2004 a controversy arose as the Montage Resort, which had recently purchased the Aliso Creek Inn and Golf Course resort, proposed to dramatically remodel and expand the property and extending it well into the park. After opposition from environmentalists and Orange County Supervisor Tom Wilson, the plans were drastically scaled down. The paved Aliso Creek Riding and Hiking Trail, constructed in sections starting in the 1970s, extends along the creek from Aliso Canyon to the Cleveland National Forest. The approximately trail is used by hikers, bicyclists and equestrians, and connects most of the major city and county parks along the creek including Aliso and Wood Canyons Wilderness Park and Laguna Niguel Regional Park, Aliso Viejo, Creekside, Sheep Hills, Sycamore, El Toro, and Heroes Parks, and Whiting Ranch Wilderness Park. In May 2012, it was named a
National Recreation Trail The National Trails System is a series of trails in the United States designated "to promote the preservation of, public access to, travel within, and enjoyment and appreciation of the open-air, outdoor areas and historic resources of the Nati ...
. The southern end of the trail terminates less than a mile (1.6 km) from Aliso Beach, with the private Aliso Creek resort in between. The county has been trying to complete the trail for many years; an early attempt in 1989 was stymied by the property owners, and a later proposal was scuttled in 2009 after the
financial crisis A financial crisis is any of a broad variety of situations in which some financial assets suddenly lose a large part of their nominal value. In the 19th and early 20th centuries, many financial crises were associated with banking panics, and man ...
. In March 2015 Mark Christy, the new owner of the resort, agreed to commit $250,000 towards designing a trail through the property as part of the new "Ranch at Laguna Beach" development, though no date has been set for its completion.


See also

*
List of rivers of California This is a list of rivers in the U.S. state of California, grouped by region. Major lakes and reservoirs, if applicable, are indicated in italics. North Coast (north of Humboldt Bay) Rivers and streams between the Oregon border and Humboldt Bay th ...
*
List of rivers of Orange County, California This is a list of rivers of Orange County, California, part of the Greater Los Angeles Area in Southern California.The Santa Ana River and San Gabriel River are the largest in Orange County; their extensive watersheds extend into neighboring ...


References

Notes Bibliography * * Durham, David L. (2001). ''Durham's Place Names of Greater Los Angeles''. Clovis, Calif.: Word Dancer Press. . * Gudde, Erwin G.; Bright, William (2004). ''California Place Names: The Origin and Etymology of Current Geographical Names'' (4th ed.). Berkeley, Calif., and London: University of California Press. . * Marsh, Lindell L.; Porter, Douglas R.; Salvesen, David; Urban Land Institute (1996)
''Mitigation banking: theory and practice''
Washington, D.C.: Island Press. . Retrieved 2010-01-28. *


External links


Aliso Creek Watershed Programs
- OC Watersheds
Aliso Creek Mainstem Ecosystem Restoration Study
- U.S. Army Corps of Engineers
Aliso Creek Estuary Restoration
- Laguna Ocean Foundation {{Greater Los Angeles Area Rivers of Orange County, California Santa Ana Mountains San Joaquin Hills Aliso Viejo, California Laguna Beach, California Mission Viejo, California Rivers of Southern California