Photos: How Rain and Floodwaters Literally Built the Southland

A swollen Los Angeles River rushes through Compton, 1926. Courtesy of the Los Angeles PublicLibrary Photography Collection.

Without rain, there would be no Southland.

Over countless millennia, rainwater scoured the mountains ringing the region. It ground granite into sand. It sloughed off topsoil. Where it issued from canyons at the base of the mountains, this muddy soup fanned out, carrying courser and then finer sediments until it merged with the cold waters of the Pacific.

As the floodwaters drained, the sediments settled, filling the deep geologic basins that abut Southern California's mountains. Eventually, these stacked sedimentary layers grew thousands of feet thick, emerging from the waters of the Pacific as flat, broad valleys like the San Fernando, San Gabriel, and Pomona, or sprawling coastal lowlands like the Los Angeles Basin and Oxnard Plain.

In the twentieth century, the metropolis hit the pause button on this natural process of land reclamation. To protect lives and capital as the city expanded into areas prone to flooding or landslides, flood control projects reconfigured the region's hydrology. Check dams and debris basins now trap sediments in or near their mountainous origins. Storm drains and flood control channels funnel rainfall to the sea as quickly as possible.

Now, those sedimentary flatlands -- home to most of the metropolis's 18 million residents -- are slowly shrinking as wave erosion and (inevitably, probably) rising sea levels encroach on the coastal plain.

Through their composition and their printed captions, the photos above and below purport to document destruction. They certainly document real human suffering. But when viewed in the context of the region's geologic history, they show the opposite of destruction; they reveal the natural forces that -- with each new flood -- created a little more Southland.

Further Reading:

• Deverell, William. "Remembering a River" in Whitewashed Adobe: The Rise of Los Angeles and the Remaking of Its Mexican Past. Berkeley: University of California Press, 2005.
• Gumprecht, Blake. The Los Angeles River: Its Life, Death, and Possible Rebirth. Baltimore: Johns Hopkins University Press, 1999.
• Orsi, Jared. Hazardous Metropolis: Flooding and Urban Ecology in Los Angeles. Berkeley: University of California Press, 2004.

A swollen Los Angeles River destroyed Los Angeles' Downey Avenue bridge in 1886.Courtesy of the USC Libraries - California Historical Society Collection.   

East Compton during the flood of 1914. Courtesy of the USC Libraries - California Historical Society Collection.

Flooding at the mouth of the Santa Ana River in Orange County in 1927. Courtesy of the Orange County Archives.

Automobiles trapped in floodwaters at 11th and Vernon Avenues in Leimert Park, 1927.Courtesy of the Los Angeles Times Photographic Archive , UCLA Library.Used under a Creative Commons license.

A swollen San Gabriel River in 1927. Courtesy of the Los Angeles Times Photographic Archive,UCLA Library. Used under a Creative Commons license.

Mud covered this automobile during a 1934 flood in La Crescenta-Montrose.Courtesy of the Los Angeles Times Photographic Archive , UCLA Library.Used under a Creative Commons license.

Flooding in Santa Ana, 1938. Courtesy of the Orange County Archives.

Flood damage to the San Gabriel Railroad bridge in Azusa in 1938.Courtesy of the USC Libraries - California Historical Society Collection.

Flooding along Buena Park's Grand Avenue in 1938. Courtesy of the Orange County Archives.

L.A. as Subject is an association of more than 230 libraries, museums, official archives, cultural institutions, and private collectors. Hosted by the USC Libraries, L.A. as Subject is dedicated to preserving and telling the sometimes-hidden stories and histories of the Los Angeles region.