The Arroyo Seco, meaning "dry stream" in

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...

, is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline data. , accessed March 16, 2011 seasonal river, canyon, watershed, and cultural area in Los Angeles County, California. The area was explored by

Gaspar de Portolà Gaspar is a given and/or surname of French, German, Portuguese, and Spanish origin, cognate to Casper (given name) or Casper (surname). It is a name of biblical origin, per Saint Gaspar, one of the wise men mentioned in the Bible. Notable peo ...

who named the stream Arroyo Seco as this canyon had the least water of any he had seen. During this exploration he met the Chief

Hahamog-na The Hahamog'na, commonly anglicized to Hahamongna and spelled Xaxaamonga in their native language, are a tribe of the Tongva people of California. Their language belongs to the Uto-Aztecan family. History The Hahamogna inhabited the Verdugo Moun ...

(Hahamonga) of 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 ...

Indians.

Waterway course

The watershed begins at Red Box Saddle in the

Angeles National Forest The Angeles National Forest (ANF) of the U.S. Forest Service is located in the San Gabriel Mountains and Sierra Pelona Mountains, primarily within Los Angeles County in southern California. The ANF manages a majority of the San Gabriel Mounta ...

near Mount Wilson in the San Gabriel Mountains. As it enters the urbanized area of the watershed, the Arroyo Seco stream flows between

La Cañada Flintridge LA most frequently refers to Los Angeles, the second largest city in the United States. La, LA, or L.A. may also refer to: Arts and entertainment Music * La (musical note), or A, the sixth note * "L.A.", a song by Elliott Smith on ''Figur ...

on the west and

Altadena Altadena () ("Alta", Spanish for "Upper", and "dena" from Pasadena) is an unincorporated area and census-designated place in the Verdugo Mountains region of Los Angeles County, California, approximately 14 miles (23 km) from the downtown ...

on the east. Just below Devil's Gate Dam, the stream passes underneath the

Foothill Freeway The Foothill Freeway is a freeway in the Los Angeles metropolitan area, California, running from the Sylmar district of Los Angeles east to Redlands. The western segment is signed as Interstate 210 (I-210) from its western end at I-5 to ...

. At the north end of

Brookside Golf Course Brookside Golf Course is a municipal golf facility located in Pasadena, California, United States. Adjacent to the Rose Bowl stadium in the city's Arroyo Seco Natural Park, the 36-hole facility offers the C.W. Koiner Course (#1) and the shorter E ...

the stream becomes channelized into a

flood control channel Flood control channels are large and empty basins which let water flow in and out (except during flooding) or dry channels that run below the street levels of some larger cities, so that if and when a flood occurs, the water will run into these ch ...

and proceeds southward through the golf course. The Arroyo Seco goes through

Pasadena Pasadena ( ) is a city in Los Angeles County, California, northeast of downtown Los Angeles. It is the most populous city and the primary cultural center of the San Gabriel Valley. Old Pasadena is the city's original commercial district. ...

, where it passes the

Rose Bowl Stadium The Rose Bowl is an outdoor athletic stadium located in Pasadena, California. Opened in October 1922, the stadium is recognized as a National Historic Landmark and a California Historic Civil Engineering landmark. At a modern capacity of an all ...

as it goes through Brookside Park. The Arroyo Seco stream, which is fed by a watershed of , helps to replenish the Raymond Basin, an aquifer underlying Pasadena that provides about half of the local water supply. This arroyo is one of two major streams that capture rainfall and storm water in Pasadena, the other being

Eaton Wash Eaton Canyon is a major canyon beginning at the Eaton Saddle near Mount Markham and San Gabriel Peak in the San Gabriel Mountains in the Angeles National Forest, United States. Its drainage flows into the Rio Hondo river and then into the Los A ...

on the eastern side of the city, which is a tributary of the Rio Hondo watershed. 2010-1101-06-ColoradoStBridge

The Arroyo Seco then passes under the

Ventura Freeway The Ventura Freeway is a freeway in southern California, United States, running from the Santa Barbara/ Ventura county line to Pasadena in Los Angeles County. It is the principal east-west route (designated north-south) through Ventura Count ...

and the Colorado Street Bridge, and it crosses the

Raymond Fault The Raymond Fault is a fault across central Los Angeles County and western Ventura County in Southern California. San Gabriel Valley area The eastern end of the Raymond Fault branches from the San Andreas Fault in the San Gabriel Mountains ...

at the southern boundary of Pasadena at the

San Rafael Hills The San Rafael Hills are a mountain range in Los Angeles County, California. They are one of the lower Transverse Ranges, and are parallel to and below the San Gabriel Mountains, adjacent to the San Gabriel Valley overlooking the Los Angeles Bas ...

. The channel continues along the western boundary of South Pasadena, then into northeast Los Angeles flowing southeast of the

Verdugo Mountains The Verdugo Mountains, also known as the Verdugo Hills or simply The Verdugos, are a small, rugged mountain range of the Transverse Ranges system in Los Angeles County, California. Located just south of the western San Gabriel Mountains, the Ve ...

and

Mount Washington Mount Washington is the highest peak in the Northeastern United States at and the most topographically prominent mountain east of the Mississippi River. The mountain is notorious for its erratic weather. On the afternoon of April 12, 1934 ...

. The Arroyo Seco then proceeds through the Los Angeles neighborhoods of Highland Park,

Hermon Mount Hermon ( ar, جبل الشيخ or جبل حرمون / ALA-LC: ''Jabal al-Shaykh'' ("Mountain of the Sheikh") or ''Jabal Haramun''; he, הַר חֶרְמוֹן, ''Har Hermon'') is a mountain cluster constituting the southern end of th ...

Montecito Heights Montecito Heights is a neighborhood in the Northeast Los Angeles region of Los Angeles, California. The population in 2000 was estimated at 16,768. Geography and transportation Montecito Heights' boundaries are roughly the Pasadena Freeway ( SR ...

, and Cypress Park. It ends at the confluence with the

Los Angeles River , name_etymology = , image = File:Los Angeles River from Fletcher Drive Bridge 2019.jpg , image_caption = L.A. River from Fletcher Drive Bridge , image_size = 300 , map = LARmap.jpg , map_size ...

near

Elysian Park Elysian Park is one of the largest parks in Los Angeles at 600 acres (240 ha). Most of Elysian Park falls in the neighborhood of the same name, but a small portion of the park falls in Echo Park. The park was created by city ordinance on April 5, ...

, north of

Dodger Stadium Dodger Stadium is a baseball stadium in the Elysian Park neighborhood of Los Angeles, California. It is the home stadium of Major League Baseball's Los Angeles Dodgers. Opened in 1962, it was constructed in less than three years at a cost of ...

and Downtown Los Angeles.Information has been derived from the archives of the Pasadena Museum of History and the Arroyo Seco Foundation. The

Arroyo Seco Parkway The Arroyo Seco Parkway, also known as the Pasadena Freeway, is one of the oldest freeways built in the United States. It connects Los Angeles with Pasadena alongside the Arroyo Seco seasonal river. It is notable not only for being an early f ...

, or Pasadena Freeway, runs parallel to the channelized Arroyo Seco from South Pasadena to the Los Angeles River.

History

Traditional narrative

Above Devil's Gate, the rapids of the Arroyo Seco are positioned so that the falls make a beating, laughing sound. In Tongva-Gabrieliño traditional narratives, this is attributed to a wager made between the river and the coyote spirit.

Early settlement

The Arroyo Seco was one of the Los Angeles River tributaries explored by Gaspar de Portola in the late summer and fall of 1770. He named the stream Arroyo Seco, for of all the canyons he had seen, this one had the least water. During this exploration he met the Chief

(Hahamonga) near Millard Canyon, at the settlement later known as Hahamongna - ''California''. This band of the

Indians would end up gathered into the fold of the San Gabriel Mission and with other bands and tribes collectively called "Gabrielenos." The Arroyo Seco region can be considered by historical accounts as the birthplace of Pasadena. After the 1820s secularization of the Missions, the broad area to the east of the Arroyo was the

Mexican land grant The Spanish and Mexican governments made many concessions and land grants in Alta California (now known as California) and Baja California from 1775 to 1846. The Spanish Concessions of land were made to retired soldiers as an inducement for ...

Rancho San Pascual Rancho San Pascual also known as Rancho el Rincón de San Pascual was a Mexican land grant in present-day Los Angeles County, California given to Juan Marine in 1834 by José Figueroa. Rancho San Pascual land now includes the cities of Pasaden ...

, present-day Pasadena, California.

Manuel Garfias Rancho San Pascual also known as Rancho el Rincón de San Pascual was a Mexican land grant in present-day Los Angeles County, California given to Juan Marine in 1834 by José Figueroa. Rancho San Pascual land now includes the cities of Pasadena ...

was the grantee of the Rancho and its longest early resident. His adobe house was on the east ridge of the Arroyo, in present-day South Pasadena. With the 1874 establishment of the community of the

Indiana Colony The Indiana Colony refers to a group of Indiana residents who settled the area known today as Pasadena, California. The group was incorporated on January 31, 1874, by Indiana residents who sought warmer weather after the exceptionally cold winter o ...

, the new residents built their homes along today's Orange Grove Boulevard, the major north–south avenue paralleling the Arroyo on the east. However, the deep and seasonally flooded Arroyo presented a barrier to easy travel and transportation between renamed Pasadena and Los Angeles. Stories of four and five hours just crossing the chasm, whether exaggerated or not, abounded in Pasadena history.''Pasadena'', Hiram Reid, 1895. Out of Print. A comprehensive history of Pasadena after 20 years of colonization. The first recorded American to live in the Upper Arroyo (north of Devil's Gate) was simply known as "Old Man Brunk". Brunk's cabin stood at a large bend in the canyon, roughly where the Forest Service housing is today. It was said he left

San Francisco San Francisco (; Spanish for " Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the fourth most populous in California and 17th ...

"for that town's good".''Altadena'' by

Sarah Noble Ives Sarah Noble Ives (March 1864 – November 1944) was an American writer, illustrator, and historian known for her children's books including ''Dog Heroes of Many Lands'' and ''Songs of the Shining Way''. Her work also appeared in publications like ...

, 1938 (Altadena Historical Society, out of print)

Transportation corridor

Dating back to the original

residents of the area, the Arroyo Seco canyon has always served as a major transportation corridor. Today it links downtown Los Angeles with Pasadena, the west San Gabriel Valley and the San Gabriel Mountains. By 1886 the

Los Angeles and San Gabriel Valley Railroad The Los Angeles and San Gabriel Valley Railroad was a railroad founded on Sept. 5, 1883, by James F. Crank with the goal of bringing a rail line to Pasadena from downtown Los Angeles. Los Angeles and San Gabriel Valley Railroad was sold and cons ...

had been established from Downtown Los Angeles with a grand wooden trestle that cut a straight line crossing from the west side to the east. The wooden trestle was replaced with the

Santa Fe Arroyo Seco Railroad Bridge The Santa Fe Arroyo Seco Railroad Bridge in Highland Park, Los Angeles, is more than long and crosses the Arroyo Seco Parkway at an elevation of over . It is the tallest and longest railroad span in the city of Los Angeles, and most likely the o ...

. Eventually this line would hook up with rail lines built from the east to create the cross-country course of the

Santa Fe Railroad The Atchison, Topeka and Santa Fe Railway , often referred to as the Santa Fe or AT&SF, was one of the larger railroads in the United States. The railroad was chartered in February 1859 to serve the cities of Atchison and Topeka, Kansas, and ...

. For local commutes, an electric traction trolley was put in and operated by the

Pacific Electric Railway The Pacific Electric Railway Company, nicknamed the Red Cars, was a privately owned mass transit system in Southern California consisting of electrically powered streetcars, interurban cars, and buses and was the largest electric railway system ...

, a Henry E. Huntington enterprise, which ran the "Red Cars" from the upper Arroyo and Pasadena through the San Gabriel Valley into Los Angeles and many points beyond.''Trolley Days in Pasadena'', 1985, Charles Seims. The lower Arroyo Seco was served by the

Los Angeles Railway The Los Angeles Railway (also known as Yellow Cars, LARy and later Los Angeles Transit Lines) was a system of streetcars that operated in Central Los Angeles and surrounding neighborhoods between 1895 and 1963. The system provided frequent local ...

"Yellow Car" lines. Arroyo Seco Bike Path Entrance

In 1900

Horace Dobbins Horace M. Dobbins (August 29, 1868 – September 21, 1962) was a Philadelphia-born businessman and politician who served as Mayor of Pasadena, California, United States in 1900-1901. Horace Dobbins was known for building the California Cyclewa ...

, Mayor of Pasadena, opened his innovative California Cycleway, an elevated wood structure with a flat planked surface that would allow bicyclers to travel from Pasadena to Los Angeles avoiding the uncertain schedules of the early trains. Dobbins was only able to build a two-mile portion of the cycleway from the Green Hotel to Raymond Hill before competition from the railroads and the growing popularity of the

horseless carriage Horseless carriage is an early name for the motor car or automobile. Prior to the invention of the motor car, carriages were usually pulled by animals, typically horses. The term can be compared to other transitional terms, such as wireless pho ...

undermined the project. Present day cycling activists are reviving a vision and plan for a dedicated bikeway from Pasadena to Los Angeles. The Arroyo Seco bicycle path now runs from Highland Park to South Pasadena; the

Kenneth Newell Bikeway The Kenneth Newell Bikeway in Pasadena is one of the first bike paths established in Los Angeles County. This “popular, well-marked bikeway” has been called “one of the premier inland trips.” The path travels through the canyon of the A ...

continues the route through Pasadena. In 1913 the Colorado Street Bridge was dedicated. This structure curves across the Arroyo accessing Eagle Rock,

Glendale Glendale is the anglicised version of the Gaelic Gleann Dail, which means ''valley of fertile, low-lying arable land''. It may refer to: Places Australia * Glendale, New South Wales ** Stockland Glendale, a shopping centre *Glendale, Queensland, ...

, and the San Fernando Valley. During the

Stock Market Crash of 1929 The Wall Street Crash of 1929, also known as the Great Crash, was a major American stock market crash that occurred in the autumn of 1929. It started in September and ended late in October, when share prices on the New York Stock Exchange colla ...

and the subsequent Great Depression of the 1930s, the bridge was a jumping off point for many committing suicide, whereby it received the ignoble name of "

Suicide bridge A suicide bridge is a bridge used frequently by people to end their lives, most typically by jumping off and into the water or ground below. A fall from the height of a tall bridge into water may be fatal, although some people have survived jump ...

." By the 1980s the bridge fell into disrepair as chunks of concrete dropped from its face to the armory parking lot in the Arroyo below. After the

San Francisco–Oakland Bay Bridge The San Francisco–Oakland Bay Bridge, known locally as the Bay Bridge, is a complex of bridges spanning San Francisco Bay in California. As part of Interstate 80 and the direct road between San Francisco and Oakland, it carries about 260,000 ...

failure in the 1989 Loma Prieta earthquake, the Colorado Street Bridge was closed as a precautionary measure. Eventually assistance from the Federal Bridge Repair and Replacement Fund and other local governmental agency discretionary funds provided funding for the complete restoration and

seismic retrofit Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent exp ...

of the bridge. The total project budget amounted to $24 million, and the Colorado Street Bridge was reopened on Dec. 13, 1993, on time and on budget.

Arroyo Seco Parkway

By mid-20th Century, the automobile had long become a mainstay of Southern California life. In 1940 the

, the first freeway, was built as a parkway alongside the newly constructed flood channel in the Los Angeles portion of the Arroyo. Today, also known as the

Pasadena Freeway Pasadena ( ) is a city in Los Angeles County, California, northeast of downtown Los Angeles. It is the most populous city and the primary cultural center of the San Gabriel Valley. Old Pasadena is the city's original commercial district. I ...

, it continues on through downtown becoming the

Harbor Freeway A harbor (American English), harbour (British English; see spelling differences), or haven is a sheltered body of water where ships, boats, and barges can be docked. The term ''harbor'' is often used interchangeably with ''port'', which is a ...

, and terminates near the harbor in San Pedro. The Arroyo Seco Corridor Management Plan was completed for the "Arroyo Seco Parkway" in 2004. The Plan was created through a partnership with the National Trust for Historic Preservation, the National Scenic Byways Center (Federal Highways), Caltrans (State Highways), the

National Park Service The National Park Service (NPS) is an agency of the United States federal government within the U.S. Department of the Interior that manages all national parks, most national monuments, and other natural, historical, and recreational propert ...

, the

Santa Monica Mountains Conservancy The Santa Monica Mountains Conservancy is an agency of the state of California in the United States founded in 1980 and dedicated to the acquisition of land for preservation as open space, for wildlife and California native plants habitat Natu ...

, and The Center for Preservation Education and Planning (CPEP Inc.). The Arroyo Seco Flood Control Channel, was built by the Works Progress Administration before and during construction of the parkway to avoid damages from future floods.

Floods and controls

The Arroyo Seco generally has a flow of several cubic feet per second, but periodically it is inundated by torrential floods from its steep, erosion-prone mountain watershed. The reputation of Arroyo Seco floods led the Spanish to site the original

Pueblo de Los Ángeles El Pueblo de Nuestra Señora la Reina de los Ángeles (English: ''The town of Our Lady the Queen of the Angels''), shortened to Pueblo de los Ángeles, was the Spanish civilian ''pueblo'' settled in 1781, which by the 20th century became the ...

away from the confluence of the Arroyo Seco and the

. Historically, these floods would race down the stream bed and overflow through Pasadena, South Pasadena, Alhambra and Los Angeles communities all the way to the Los Angeles River. As Los Angeles developed into a city and grew outwards, the damage from these floods was particularly severe in 1914 and 1916.

Devil's Gate Dam

In 1920, the

Los Angeles County Flood Control District The Los Angeles County Department of Public Works (LACDPW) is responsible for the construction and operation of Los Angeles County's roads, building safety, sewerage, and flood control. DPW also operates traffic signals and intelligent transpor ...

built the first flood control dam in Los Angeles County at Devil's Gate gorge. Named for a rock outcropping which resembles the face of a devil, this is the narrowest spot on the Arroyo Seco's course below Millard Canyon. The construction was by the Bent Brothers Company. Devil's Gate Dam in the Arroyo Seco in northern Pasadena between

and

is managed by the

Los Angeles County Department of Public Works The Los Angeles County Department of Public Works (LACDPW) is responsible for the construction and operation of Los Angeles County's roads, building safety, sewerage, and flood control. DPW also operates traffic signals and intelligent transpor ...

The flood basin above the dam captures the flows of the mountain watershed of the Arroyo Seco. This area is now called " Hahamongna", a phrase meaning "Flowing Waters, Fruitful Valley". Hahamongna also refers to the original Native American tribe of the Tongva Indians who once inhabited the area. In 2011, the flood basin had filled with debris brought down after the 2009 Station Fire, reducing its effectiveness as a flood control measure. The County of Los Angeles conducted public hearings on the Environmental impact statement before selecting a method to remove debris from the Hahamongna area. In 2014, the Board of Supervisors approved a five-year project to remove 2.4 million cubic yards of sediment () from the basin despite strong opposition from neighbors and recreational enthusiasts. The opponents contended that hundreds of trucks would be required that would increase pollution and noise. They also said that the wildlife habitat would be destroyed and interfere with hikers, cyclists and horseback riders who use the area for recreation. The alternative supported by Pasadena officials would have removed 1.4 million cubic yards of sediment () and provided regular maintenance. County officials supported removing more sediment to reduce the flood risk for most major storms, the work having begun in early-2019. Below Devil's Gate Dam, most of the Arroyo Seco creek, with two short exceptions, is contained in a concrete channel that contains stormwater and municipal runoff. This channel and other similar flood control structures throughout the

Los Angeles Basin The Los Angeles Basin is a sedimentary Structural basin, basin located in Southern California, in a region known as the Peninsular Ranges. The basin is also connected to an wikt:anomalous, anomalous group of east-west trending chains of mountai ...

and along the foothills of the San Gabriel Mountains were built following the devastating

Los Angeles Flood of 1938 The Los Angeles flood of 1938 was one of the largest floods in the history of Los Angeles, Orange, and Riverside Counties in southern California. The flood was caused by two Pacific storms that swept across the Los Angeles Basin in February-Ma ...

Restoration programs

For more than one hundred years, the natural environment of the Arroyo Seco and its proximity to a large urban population have inspired efforts to protect, manage and preserve it. L.A. County flood control was first founded in an effort to control the wild waters of the Arroyo Seco and

Charles Lummis Charles Fletcher Lummis (March 1, 1859, in Lynn, Massachusetts – November 25, 1928, in Los Angeles, California) was a United States journalist, and an activist for Indian rights and historic preservation. A traveler in the American Southwest, ...

founded the Arroyo Seco Foundation in 1905 for the purpose of preserving recreational use and habitat, residents in Los Angeles and Pasadena contributed generously to efforts to buy up open space in the great canyon to protect for future generations. There has been a series of studies conducted to assess and improve the management of the Arroyo Seco Watershed. These include:

Restoration goals

# Restore full flood control functions in the Arroyo Seco area. # Better manage, optimize, and conserve water resources while improving

water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...

. # Improve

regional park A regional park is an area of land preserved on account of its natural beauty, historic interest, recreational use or other reason, and under the administration of a form of local government. Definition A regional park can be a special park distri ...

recreational opportunities and enhance

nature reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological or ...

open space. The restoration efforts are being carried out by the County of Los Angeles and local cities, primarily the City of Pasadena.

Jet Propulsion Laboratory - NASA

Early rocket-engine-testing began in the Arroyo Seco in 1936 and this led to the establishment of the

Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States. Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...

(JPL) at the mouth of the Arroyo Seco by the

California Institute of Technology The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...

. During the 1950s, JPL was heavily involved in rocket testing, and the roar of rocket engines could be heard emanating from the Arroyo Seco area for miles. These rocket projects were terminated at the facility by 1958. By the mid-1960s, JPL had become instrumental in the development, launching, and tracking of a number of unmanned near-Earth and deep-space

space probe A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; or ...

s for the National Aeronautics and Space Administration. One notable project was the

Mars Rover A Mars rover is a motor vehicle designed to travel on the surface of Mars. Rovers have several advantages over stationary landers: they examine more territory, they can be directed to interesting features, they can place themselves in sunny pos ...

, which has returned a number of panoramic photos of the

Martian Mars, the fourth planet from the Sun, has appeared as a setting in works of fiction since at least the mid-1600s. It became the most popular celestial object in fiction in the late 1800s as the Moon was evidently lifeless. At the time, the pr ...

surface. JPL has been criticized by regional environmentalists and the community for its

water pollution Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. ...

of the local

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...

with

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

chemicals, such as

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

s and

perchlorate A perchlorate is a chemical compound containing the perchlorate ion, . The majority of perchlorates are commercially produced salts. They are mainly used as oxidizers for pyrotechnic devices and to control static electricity in food packaging. Per ...

rocket fuel Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical ...

accelerant Accelerants are substances that can bond, mix or disturb another substance and cause an increase in the speed of a natural, or artificial chemical process. Accelerants play a major role in chemistry—most chemical reactions can be hastened with an ...

s. A monumental cleanup project by NASA has begun, which includes a multimillion-dollar pumping and water filtration system to treat the groundwater, removing toxins until the aquifer contamination level has been reduced below their federally-specified limits. This project is carried out by a NASA project team and monitored 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 ...

. Frequent public meetings are held with public comment, and recorded for the record on the quality and progress of the clean-up.

Trout Restoration

Before channelization, the Arroyo Seco was a spawning habitat for Southern

Steelhead 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 ...

, the Anadromous form of rainbow trout. The Arroyo was home to a resident rainbow trout population until at least 2009, when mudslides following the Station Fire (2009) were thought to have wiped out the population. In November 2020, the California Department of Fish and Wildlife transplanted almost 500 trout from the

West Fork San Gabriel River The West Fork is one of two major streams, the other being the East Fork, that combine to form the San Gabriel River in Los Angeles County, California. The West Fork flows for in an easterly direction from its origins at Red Box Gap, in the San ...

, definitively re-establishing the presence of native trout in the stream.

Crossings

From mouth to source (year built in parentheses): *Railroad *North Avenue 19 - twin bridges (1956) *North

San Fernando Road San Fernando Road is a major street in the City of Los Angeles and Los Angeles County. Within the Burbank city limits it is signed as San Fernando Boulevard, and north of Newhall Pass it is signed as The Old Road. It was previously designate ...

(1913) *

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 ...

Golden State Freeway Interstate 5 (I-5) is a major north–south route of the Interstate Highway System in the United States, stretching from the Mexican border at the San Ysidro crossing to the Canadian border near Blaine, Washington. The segment of I-5 in ...

and ramps (1962) *West Avenue 26 (1939) *Southbound State Route 110 ramp to Interstate 5 (1962) *Interstate 5 ramp to northbound State Route 110 (1962) *Cypress Avenue edestrian Bridge*Railroad - Metro L Line *Pasadena Avenue (1940) *State Route 110 ramps to East Avenue 43 (1940) *East Avenue 43 (1939) *Sycamore Grove Park edestrian Bridge*South/East Avenue 52 (1940) *Via Marisol riginally Hermon Avenue(1940) * edestrian Bridge*South Avenue 60 (1909) *State Route 110 ramps to South Avenue 60 (1940) * Railroad - Metro L Line *Marmion Way (1940) and California 110 Offramp (1940) *York Boulevard (1912) *State Route 110 - Pasadena Freeway (1939) *San Pasqual Avenue (1939) *Dirt road *South San Rafael Avenue (1922) *La Loma Road (1914) *South Arroyo Park dirt road *South Arroyo Park edestrian Bridge* Colorado Street Bridge carrying West Colorado Boulevard (1913) * State Route 134 -

(1953) *North Arroyo Boulevard (1927) *West Holly Street (1925) *Seco Street (1939) * Rose Bowl Parking Lot Pedestrian Bridges*

Pedestrian Bridges*West Washington Boulevard (1939) *Brookside Golf Course edestrian Bridge* Interstate 210 - Foothill Freeway (1974) *Oak Grove Drive (1955) *Devil's Gate Dam *Explorer Road *Forest Route 2N70 (2002)

Attractions and landmarks

Upper Arroyo - mountains section

The many the Arroyo Seco is one of the most popular hiking spots in Southern California. The mountainous part of the Arroyo Seco is located within the

Angeles Crest Highway The Angeles Crest Highway is a two-lane (one lane of travel in each direction) highway over the San Gabriel Mountains, in Los Angeles County, California. Its route is to/through the San Gabriel Mountains National Monument and the Angeles Nation ...

skirts the western edge of the Arroyo Seco Canyon. The following is a list of Forest Service facilities in the Upper Arroyo, from south to north: *Forest Service Employee Housing w/ attached public hitching rail and horse trough *Teddy's Outpost Picnic Area *Gould Mesa Campground *Niño Picnic Area *Paul Little Picnic Area *Oakwilde Campground *Commodore Perry Switzer Trail Camp *Switzer's Picnic Area *Red Box Station (at the canyon's head) *Switzer Falls *Dawn Mine *Bear Canyon *Millard Canyon - Millard Canyon Falls Millard Canyon, located near the mouth of the Arroyo, is a delightful canyon with an impressive

waterfall A waterfall is a point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf. Waterfalls can be formed in severa ...

. Sunset Ridge The trail skirts the eastern side of the canyon, the eastern boundary of the Arroyo Seco Watershed. Millard Canyon was a major pedestrian thoroughfare for

Serrano people The Serrano are an indigenous people of California. They use the autonyms of Taaqtam, meaning "people"; Maarrênga’yam, "people from Morongo"; and Yuhaaviatam, "people of the pines." Today the Maarrênga'yam are enrolled in the Morongo Band o ...

, and other Californian Native Americans traveling between the

coastal plain A coastal plain is flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and a piedmont area. Some of the largest coastal plains are in Alaska and the southeastern United States. The Gulf Co ...

, the San Gabriel Mountains, and the

Mojave Desert The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily ...

regions of Southern California. Brown Mountain Truck Trail, which begins near the confluence of El Prieto Canyon and proceeds across the front range of the San Gabriel Mountains to upper Millard Canyon, offers impressive vistas of the San Gabriel Valley. The Burton Trail descends from this road to the upper stretches of the Arroyo near Oakwilde Campground. The

Gabrielino Trail The Gabrielino Trail is a United States National Recreation Trail that runs through the Angeles National Forest with trailheads at Windsor Avenue in Altadena, California on the west end and Chantry Flat, just north of Arcadia, California, on the e ...

, which is a popular journey for hikers, equestrians and bicyclists, travels up the steep canyon. A popular hike on the Gabrielino Trail is the 4 mile round trip to lower Switzer Falls from Switzer Picnic area.

Lower Arroyo - urban section

NASA *Oak Grove Disc Golf Course *Hahamongna Watershed Park - ''(formerly "Oak Grove Park")'' *Devil's Gate Dam *

* Rose Bowl - stadium and flea market *Brookside Park *

Kidspace Children's Museum Kidspace Children's Museum is a children's museum in Pasadena, California. It is located next to the Rose Bowl, in the former Fannie E. Morrison Horticultural Center. History Since the December 2004 opening of its new facility in Brookside Par ...

* Colorado Street Bridge * Hotel Vista Del Arroyo - ''United States 9th District Court of Appeals'' *Lower Arroyo Park Archery Range *Pasadena Roving Archers *Pasadena Casting Club *

Lower Arroyo Seco Historic District The Lower Arroyo Seco Historic District is a residential historic district in Pasadena, California, Pasadena, California. The historic district encompasses homes located near the lower Arroyo Seco (Los Angeles County), Arroyo Seco along Arroyo Bo ...

, including the Batchelder House - '' Arts and Crafts Movement'' * Arroyo Parkway *

Metro Metro, short for metropolitan, may refer to: Geography * Metro (city), a city in Indonesia * A metropolitan area, the populated region including and surrounding an urban center Public transport * Rapid transit, a passenger railway in an urb ...

L Line (Bridge crossing and Ave 57 Street Station) *

Southwest Museum of the American Indian The Southwest Museum of the American Indian is a museum, library, and archive located in the Mt. Washington neighborhood of Los Angeles, California, above the north-western bank of the Arroyo Seco (Los Angeles County) canyon and stream. The muse ...

* "El Alisal"—Lummis House - ''historic home museum and

native plants In biogeography, a native species is indigenous to a given region or ecosystem if its presence in that region is the result of only local natural evolution (though often popularised as "with no human intervention") during history. The term is equi ...

garden A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate bot ...

s''. *

Heritage Square Museum Heritage Square Museum is a living history and open-air architecture museum located beside the Arroyo Seco Parkway in the Montecito Heights neighborhood of Los Angeles, California, in the southern Arroyo Seco area. The living history museum sho ...

- ''historic Victorian houses park''. *Los Angeles River Center and Gardens Park . accessed 7/22/2010 *Confluence of the Arroyo Seco and Los Angeles River

Gallery

References

External links

Arroyo Seco FoundationCity of Pasadena: Arroyo Seco websiteArroyo Seco Neighborhood Council
— ''City of Los Angeles neighborhood council for communities/neighborhoods in the Arroyo Seco.''
Angeles National Forest website
{{Authority control Canyons and gorges of California Rivers of Los Angeles County, California Tributaries of the Los Angeles River Washes of California Landforms of Los Angeles County, California Los Angeles County, California regions San Gabriel Mountains San Gabriel Valley San Rafael Hills Geography of Los Angeles Geography of Pasadena, California Geography of the San Gabriel Valley Angeles National Forest Altadena, California Cypress Park, Los Angeles Highland Park, Los Angeles La Cañada Flintridge, California Montecito Heights, Los Angeles Mount Washington, Los Angeles Northeast Los Angeles South Pasadena, California History of Los Angeles History of Los Angeles County, California History of Pasadena, California Works Progress Administration in California Rivers of Southern California