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Channelization of the Arroyo Seco

For hundreds of years, the Arroyo Seco was a central life-giving resource for first the Tongva people, and then the successive waves of settlers. A seasonal tributary of the Los Angeles River, the Arroyo provided water, food, transportation and—perhaps most importantly—meaning to the communities along its banks. But a series of changes would sour that long and fruitful relationship. Between the completion of the Owens Valley Aqueduct in 1913 and the Colorado River Aqueduct in 1935, as well as a series of disastrous floods throughout the decades, the Arroyo Seco (and the Los Angeles River in general) turned from essential to the city's growth, to being seen as an obstacle to its expansion.

The efforts of local governments to control floods had long been inadequate, but a unique series of events—namely the Great Depression and the New Deal—opened the door to the first truly systemic attempt to manage the Arroyo Seco. Engineers embarked on a study (the first ever) of the hydraulic properties and the history of flooding in the 1930s, and the result was a flood-control proposal that included plans to segment large portions of the Los Angeles River, diverting and confining it into concrete channels.

The channelization of the Arroyo Seco, which began in 1935, was initially a boon to the local economy. The employment opportunities offered by the massive project were welcomed by workers still frozen out of jobs by the Great Depression. There was plenty of work to do, as the channelization was not the only structural change to the Arroyo Seco. Plans for a parkway through the canyon were well underway by the time construction on the channel commenced. Confinement of the river to a channel allowed the parkway to be realized; the parkway's integrity could no longer be endangered by the river's seasonal flooding. Between 1935 and 1940, the Works Progress Administration spearheaded the channelization of the river as part of the construction of the Arroyo Seco Parkway.

The completion of channelization effectively tamed the river and brought systemic order to the basin. The Edenic features of the Arroyo Seco that had played such an important role in drawing people to the area, however, began to vanish with the structural developments. The environmental impact of the project, including its adverse effect on water quality and damage to the native riparian habitat, proved to be detrimental. Decades would pass before the health of the Arroyo Seco's ecosystem would be cogently addressed.

 

The Desire to Control Nature
William Deverell describes the challenges and tensions of the region, with changes in the scale of the neighborhood despite nature's limitations.

 

Channelization
Timothy Brick details the channelization of the Los Angeles River.

 

Arroyo Seco Channelization 1
Despite the name Arroyo Seco, meaning "Dry Stream," heavy rains easily pushed its river channels to its limits, causing a flood every few years. | Image courtesy of the Los Angeles Public LIbrary
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The first serious flood in Los Angeles County to be recorded occured in 1884. | Image courtesy of the Los Angeles Public LIbrary
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Collapsed bridge caused by flood waters in the Arroyo Seco, 1913. | Image courtesy of the Los Angeles Public LIbrary
Arroyo Seco Channelization 4
Plans to construct concrete walls along the Arroyo were first discussed in 1914. | Image courtesy of the Los Angeles Public LIbrary
Arroyo Seco Channelization 5
A series of floods prompted the creation of the Los Angeles County Flood Control District in 1915. | Image courtesy of the Los Angeles Public LIbrary
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In 1916 Pasadena gave Los Angeles County an easement to build a dam in the Arroyo Seco. | Image courtesy of the Los Angeles Public LIbrary
Arroyo Seco Channelization 7
Devi's Gate Dam was completed in 1920, the first dam to be built by the Los Angeles County Flood Control District. | Image courtesy of the USC Digital LIbrary
Arroyo Seco Channelization 8
Even after the construction of Devil's Gate Dam, the Arroyo Seco continued to swell up after a large storm, as seen in this aerial photo ca.1930. | Image courtesy of the USC Digital Library
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Channelization of the Arroyo Seco began in 1934. | Image courtesy of the USC Digital Library
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Excavation in the main channel east of Sycamore Grover Park, February 1937. | Image courtesy of the USC Digital Library
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Portions of the Arroyo Seco near Rose Bowl were already channelized by 1936, when this photo was taken. | Image courtesy of the USC Digital Library
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Construction of the Avenue 43 bridge across the Arroyo Seco began in 1938. | Image courtesy of the USC Digital Library
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Parts of the Arroyo Seco channelization was completed as part of the Works Progress Adminstration in 1938. | Image courtesy of the USC Digital Library
Arroyo Seco Channelization 14
Concurrent to the channelization efforts, construction of the Arroyo Seco Parkway began in 1938. | Image courtesy of the USC Digital Library
Arroyo Seco Channelization 15
In 1939, $2.18 million were allocated for the Arroyo Seco flood control project, from a total $237 million in Federal funds for L.A. County flood control programs. | Image courtesy of the USC Digital Library
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Arroyo Seco from old railroad trestle north of Avenue 26, looking north toward Pasadena Avenue, 1940. | Image courtesy of the USC Digital Library
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Water entering the concrete channel of the swift-flowing waters of the Arroyo Seco from a spillway at Ave. 43 on February 28, 1941. | Image courtesy of the Los Angeles Public Library
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The channelization of the Arroyo Seco was completed in 1947, covering the entire length, with the except of two small sections, in concrete. | Image courtesy of the USC Digital Library
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Confluence of Arroyo Seco and the Los Angeles River, just south of the Pasadena Freeway. The original Pueblo de Los Angeles had been sited away from this confluence to avoid the floods. | Image courtesy of the Los Angeles Public Library
Arroyo Seco Channelization 20
Since the channelization, the appearance of the Arroyo Seco has remained very much the same. Today, efforts are underway to revitalize the river, including construction of a bike path and plans to bring the channels back to its original state by removing the concrete. | Image courtesy of the Los Angeles Public Library