The Devastating Floods of 1868: Downey Was Born in a Floodplain

In late 1868, the area that is now Downey was called Los Nietos, after the vast Rancho Los Nietos land grant. It was farmland on the floodplain between two rivers, and that winter the rivers demonstrated exactly what that meant.

What the newspaper reported

The Los Angeles Semi-Weekly News of December 3, 1868 carried an account of severe losses in Los Nietos. The named landowners give a sense of the scale.

Governor Downey is the man the city is named for — the former and youngest-ever governor of California, born in Ireland, who pioneered modern subdivision on land he acquired between the Rio Hondo and the San Gabriel River around 1865. Pío Pico was the last governor of Alta California under Mexican rule.

The Murphy family's night

The account of what happened to the Murphys is worth reproducing in outline, because it conveys what a floodplain event actually meant before flood control.

When the river began rising on the Monday evening, Mr. Murphy and his family — fearing water reaching the floor of the house — set out to wade to high ground. Mr. Murphy and three of the children made it to safety. Mrs. Murphy, her daughter, and a Mr. Casserly did not. They were caught by the water and managed to reach a drift, where they remained from four o'clock in the afternoon until midnight, when they were finally reached by a boat built for the emergency.

Eight hours clinging to accumulated debris in a flooding river, waiting for a rescue boat that had to be constructed on the spot.

The river moved

The most remarkable consequence was geographic. The floods of 1867–1868 caused the San Gabriel River to abandon its former channel and take a new course.

A river relocated itself by several miles in a single wet season, and the two channels that now define Downey's eastern and western edges are the before and after of that event. The relocated watercourse also washed away a substantial part of Pío Pico's house.

Why this stopped happening

The nineteenth and early twentieth centuries produced repeated flood catastrophes across the Los Angeles basin, and the eventual response was the Los Angeles County Flood Control District and the system it built.

Both the San Gabriel River and the Rio Hondo were channelized in concrete, fixing them permanently in place. Whittier Narrows Dam was built upstream at the gap where both watercourses pass through, controlling the flows that would otherwise reach the Downey basin.

It worked. Rivers in this basin do not relocate themselves any more, and the kind of event that stranded the Murphy family does not happen here now.

What replaced it

Downey's flood risk did not disappear — it changed form. Climate risk modeling puts roughly 24% of Downey buildings at meaningful flood exposure today, with five census tracts above 50%.

The mechanism is now urban rather than riverine. A dense, heavily paved city sheds rain rather than absorbing it, so the storm drain system carries the entire load. When rainfall intensity exceeds its design capacity — as it did repeatedly during the nine consecutive atmospheric rivers that hit California in three weeks over December 2022 and January 2023 — water backs up at the inlets and finds the lowest doorway.

There is a local echo of this within living memory. Before storm drains were installed in the northern part of the city in the summer of 1957, Firestone Boulevard ran like a river in heavy rain, and merchants kept sandbags at their doorways as a matter of routine.

Why the history is still useful

Two practical reasons.

First, it explains the ground. Downey's soil is river-deposited alluvium laid down by exactly these events — clay-rich, water-retentive, and seasonally expansive. That soil is why slab leaks are so common here, why cast-iron drain lines crack, and why clay-tile sewer joints work open enough for roots to enter.

Second, it explains the geography of risk. The lowest ground near the river channel — the Rio San Gabriel neighborhood, and South Downey below Imperial Highway — is low because of where the water used to go. It still goes there when the drains are overwhelmed.

The engineering changed what a flood looks like in Downey. It did not change the elevation of the ground.