The dam was completed prior to the catastrophic Los Angeles Flood of 1938 , the most severe flood recorded in Southern California since the Great Flood of 1862 . Along with San Gabriel Dam , which at the time was under construction , the Cogswell Dam upstream and the Morris Dam greatly reduced the flood peak on the San Gabriel River , saving downstream cities millions of dollars ' worth of damages . If it were not for the three dams , the flow past Azusa may have exceeded , but was limited to just , with Morris Dam alone reducing the flood peak by some
Great Flood of 1862
Great Flood of 1862
Morris Dam