Most of the time, the L.A. river seems little more than a pathetic trickle. But then one of L.A.’s, like, two annual rainy days rolls around and suddenly it becomes a real river. A real river, guys! Our city has a river! Like the Thames or the Mississippi or the Nile or the Ganges or… not really like any of those at all, actually. Still it’s incredible to drive across 1st Street Bridge and see the concrete channel full to the brim with rushing, murky rainwater. Days like these are the reason the L.A. River exists in the first place—or rather, the reason it exists as a post-apocalyptic concrete-lined ditch.

The river used to be wildly temperamental, changing course all over the place when there was major winter precipitation. In 1938, a five-day storm resulted in floodwaters that swept across the city—one of the greatest disasters in L.A.’s history. The swollen river swept over swaths of the Valley, Venice, Compton, and Long Beach, leaving staggering destruction in its wake. 144 people were killed. The course of the river shifted up to a mile in some areas.

Photograph courtesy Los Angeles Public Library/Herman J. Schultheis Collection

Photograph courtesy Los Angeles Public Library/ Herald-Examiner Collection

Photograph courtesy Los Angeles Public Library/Herman J. Schultheis Collection

After the flood, the Army Corps of Engineers came in and supervised the construction of the concrete channel we know today, to ensure that the river stays put. The end result may be an eyesore for some and a source of inspiration for others, but hey—at least now we can fully embrace the joy of rain, without having to worry about Bell Gardens getting washed away.

Thomas Harlander is a staff writer at Los Angeles magazine. You can follow him on Twitter and Instagram. He recently wrote “This Iconic Downtown Police Station Is Facing Demolition.”