Arroyo Seco Floods Led to Devil’s Gate Dam

Those with a sense of history have gotten used to the idea that our small streams and dry stream beds become roaring torrents when even a moderate rainfall hits the San Gabriel Mountains. One of the classic examples is the Arroyo Seco. It runs from its headwaters high in the San Gabriels, down past La Cañada, all the way to just above Los Angeles where it empties into the Los Angeles River. It normally flows in a gentle gurgling stream and even running dry in summer. 

As a matter of fact its name, Arroyo Seco, actually is Spanish for “dry creek.” When members of the Portola Expedition crossed the Arroyo on their way north in 1770, it was late summer and the bed of the stream was dry so they named it Arroyo Seco. The Native Americans knew the truth though that the Arroyo ran in violent torrents in the winter. With several thousand years of experience, they sited their villages well away from the stream bed. Even the Spanish learned this as well – often the hard way.

The Americans were not as wise. The first inkling of the power of Arroyo floods came in 1862. A steady series of storms (an estimated 50 inches) caused the Arroyo Seco to pour into the LA River with such force that it carried away the pueblo’s early water works situated on the bank opposite. It flooded again in 1868. In 1869, a naïve Easterner built a resort at the side of the Arroyo in today’s Highland Park and it was flooded repeatedly. 

In the boom of the 1880s, towns began to be built along the Arroyo, along with rail lines to serve them, and that’s when the real trouble began. Floods in 1882 and 1884 claimed the first life, a dairyman who tried to cross the roaring stream with his wagon. He would not be the last. More floods in the late 1880s carried away rail lines and newly-built bridges along the Arroyo. A few houses built along the banks were swept away. Each time the floods subsided, the stream returned to its gently flowing appearance, luring new residents to build closer to the river’s edge.

Then there came a couple of decades of less rainfall. Building resumed in areas that had previously flooded and more bridges were built crossing the tiny stream. To compound the potential for danger, the forests of the San Gabriels were cut down and the hillsides burned in months-long wildfires, increasing the likelihood of flooding. In the early 1900s, even normal rainfall created deadly floods.