Monday November 9, 2026
USC Viterbi —
Seasonal climate forecasts estimate how El Niño may affect Southern California’s rainfall. I study the next stage: what happens once that rain reaches the ground and how quickly runoff enters and moves through the Los Angeles River before reaching the ocean.
Much of the Los Angeles watershed is paved or developed, so relatively little rain infiltrates the ground. During an intense storm, debris-laden runoff rapidly drains into tributaries and the main channel. In the El Niño winter of 1982–83, peak flow near Long Beach exceeded 80,000 cubic feet per second. Storms caused hundreds of millions of dollars in damage across California, although Los Angeles’ flood-control system prevented substantially greater losses.
Since the river was channelized in the mid-20th century, its channels, dams and upstream flood-control basins have managed several wet winters effectively. Managers use short-range rainfall forecasts and real-time measurements to keep enough storage available in the basins to capture runoff, then release water into the channels when conditions allow.