During January and February 1980, storms caused substantial rises in streamflow throughout much of California. In mid-January flooding occurred in the foothills of the Sierra Nevada and in the central coast area. In late January and mid-February, high floodflows in streams in coastal southern California caused much damage and several deaths. The Tijuana River in northern Baja California and southern San Diego County flooded many square miles of lowlands as its flow during two separate flooding episodes exceeded all records. Most reservoirs in San Diego County spilled, several for the first time since their completion. Lake Elsinore, in eastern Riverside County, caused damage to lakeside property as it filled to an elevation not reached since 1916. February flooding in southern California was caused by a series of storms separated by short intervals. Some peaks of record were observed, and streamflow throughout the area remained high for a relatively long period. In many streams, the volume of sustained flow for periods of 7 and 15 consecutive days were the greatest that have occurred during the period of record.

The unreliability of the San Diego River compelled the Franciscan fathers to construct the area's first dam in 1813 to conserve drinking and irrigation water for the Mission San Diego de Alcalá. This water-driven circumstance continued and expanded in the ensuing American era. Lacking a reliable water source at the turn of the 20th century, San Diego County was destined to experience modest growth. The region's semiarid conditions, cyclical droughts, and existing river systems determined that the only effective way to maintain a ready water supply was to conserve runoff and river floodwaters behind dam-created reservoirs. Between 1888 and 1934, private and municipal interests constructed a series of massive structures that made San Diego County the dam-building center of the world. The county featured some of America's first multiple arch dams and earliest hydraulic fill dams. Into the mid-1940s, dammed reservoirs remained the principle water source for county consumers and made the municipal expansion of the city of San Diego possible.