Fifty-five years ago, Boca Reservoir stood alone as flood protector on the Truckee River. In 1950, record-setting rains before Thanksgiving overwhelmed the small solitary dam. Torrents of water poured over Boca’s spillway and added to the destructive flow rushing downstream.

Damage in Floriston, Reno and Sparks was extensive. The Thanksgiving flood of 1950 prompted the Bureau of Army Engineers and the Bureau of Reclamation to plan the construction of additional reservoirs in the Truckee watershed. Current flood control uses the Prosser Creek, Boca, Martis, and Stampede reservoirs. Gates on Donner Lake and Lake Tahoe provide some control on those watersheds.

But even with this hydrologic safety net, sometimes little can be done to control the wild and unpredictable Truckee River.Saturated soil and snowStorms came unusually early in 1950. During September and October, precipitation in the northern Sierra exceeded 300 percent of normal.

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By November the soil was saturated and snow lay 4 feet deep in the upper elevations. On Nov. 13, a moisture-laden monster storm plowed in from the Pacific Ocean. A strong jet stream energized this potent weather system and forced the saturated air mass over the Sierra. Heavy snow fell in the mountains, but that soon turned to rain as the tropical nature of the storm grew more dominant. When this weather pattern stalled over Northern California, the stage was set for disaster.

For nine consecutive days, heavy rain drenched the Sierra. The tropic-like downpours quickly melted the high elevation snowpack in what hydrologists call a “wet mantle” flood event where rain and melting snow combine to generate exceptional runoff.

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On the Sierra west slope, nearly 27 inches of rain fell at Blue Canyon. The normally peaceful Yuba River exploded into a raging torrent. Floodwaters 4 feet deep flowing over Highway 40 closed the road at Cisco, 25 miles west of Truckee. About 500 feet of Highway 50 was washed out near Twin Bridges. Both of these vital trans-Sierra highways were shut down for 10 days.

Donner Lake soon hit flood stage and washed out the bridge over Donner Creek on southbound Highway 89, while Truckee’s school closed when high water flooded the furnace. North of Truckee, Highway 89 was underwater and the Feather River Canyon was clogged by rock slides.

A massive mud slide near Emigrant Gap and a washout at Floriston forced Southern Pacific to cancel all trains over the Sierra. Luxury streamliner “City of San Francisco” was caught between the blockades and spent the night parked at Norden on Donner Pass. Two years later this upscale passenger train would be trapped in snow for three days near Yuba Gap. Only United Airlines could offer transport from Reno to California.

More than 10 inches of rain fell in Tahoe City in one week. Alex Cushing, a founder of the Squaw Valley ski area, and about 30 workers were trapped in the valley when Squaw Creek washed out both bridges into the resort. Lake Tahoe’s surface elevation rose 15 inches but still remained 2.5 feet below the legal maximum. Tahoe’s 17 gates remained closed but the Truckee River drew strength from countless feeder streams.

Mountain watersheds damaged by over-cutting timber or animal over-grazing allowed even more water to race down the slopes. Gushing Pole Creek joined forces with the Truckee River and added to the powerful current. This confluence helped destroy the Big Chief bridge and flood dozens of cabins and summer homes between Lake Tahoe and Truckee. In Truckee more than 11 inches of rain fell in eight days.

Water inundated buildings and backyards of homes close to the river. In Tahoe City ponderous pines toppled over in the saturated soil. A summer home owned by Alice Griffith was destroyed when a giant tree 6 feet in diameter lost its moorings. In California the widely destructive floods in the Central Valley were the greatest since before the turn of the century. Levee systems from Marysville to Bakersfield failed when rivers draining the Sierra ran amok. California Gov.

Earl Warren proclaimed a state of emergency. Some 670,000 acres of farmland were flooded, 25,000 people were evacuated and property damage exceeded $33 million. Boca overloadAlong the Sierra east slope the situation was critical along the Truckee River. At first, the vital Boca Reservoir absorbed the incredible runoff, but the incessant storms proved overwhelming for its limited capacity. On Nov. 19 a super-saturated storm cell slammed against the mountains where it burst like a water-filled balloon.

The downpour dumped 3.12 inches of rain on Carson City in just 24 hours, a record that still stands. Boca Reservoir topped out and 5,000 cubic feet of water per second poured uncontrolled over the spillway.

That additional flow rushed into the Truckee River and reinforced the flood crest surging down from the mountains. The rapid rise led to a rumor that Boca Dam had collapsed, but Walter Bell, watermaster for the area, quickly squelched the tale. Boca was holding, but the water just kept on coming. Despite Bell’s confidence, the Reno fire department prudently moved two pumpers and a ladder truck to a safer distance away from the river.

The Truckee River was ripping out anything that stood in its way. Mrs. Byron Miller was returning home to Floriston at 6:30 p.m. on Nov. 19. The 18-ton Floriston Bridge seemed to be anchored securely, but Miller stopped her car anyway as a precaution. Everything looked safe so she put the car in gear and slowly started forward. Just as she edged out onto the bridge, the whole span collapsed into the muddy torrent.

Fortunately for Mrs. Miller, the front bumper hooked on some debris and held the car until a tow truck arrived in time to pull her to safety. Down river the floodwaters washed out 800 feet of Highway 40. At Verdi, the Highland ditch was dynamited to release floodwaters into nearby fields. Everyone could see that the Truckee River flood-control system had over-loaded. Reno residents and business owners were now vulnerable to the unchecked onslaught of the rampaging Truckee.

Muddy water 4-feet deep swept through Reno’s downtown district. Floodwaters poured over the Virginia Street Bridge and washed out the Rock Street Bridge; soon all spans across the river were closed for safety. National Guard Troops joined emergency workers sandbagging the beleaguered city.

When emergency pumps in the basement of the Reno Evening Gazette failed, water poured in and flooded the presses. In order to publish at least a brief account of the ongoing disaster, some of the Gazette’s printing type was taken to the Silver State Press.

They managed to produce a single sheet, printed on both sides. Five hundred of these limited flood editions were distributed from the Gazette’s main office. Despite the flood, tourists still found their way into downtown casinos. Adventurous gamblers at the Mapes and Riverside casinos were seen playing slots dressed in rubber hip boots.

Finally on Nov. 22, the day before Thanksgiving, the deluge ended and a warm sun sparkled in clear blue skies. Downtown Reno streets were piled high with muddy office furniture, equipment and Christmas goods that had been stored in the flooded basements. There had been no warning to move supplies to higher ground. Deep water still covered the rich farmlands of the Carson Valley, but it was subsiding.

Only one fatality could be directly attributed to the flood, but the monetary loss for western Nevada was $6 million.Flood protectionSince 1950 additional reservoirs have been built in the Truckee River watershed, which have boosted flood protection for downstream communities, but the system is still not foolproof. (Remember the devastating floods in Feb. 1986 and the New Year’s Flood of 1997?)

The observations from a Truckee Meadows farmer should be well-heeded. In answer to a government engineer’s question about the “average flow of the river” he responded, “Mr. Engineer, the Truckee doesn’t flow in averages. It comes in floods.”

Mark McLaughlin’s column, “Weather Window,” appears monthly in the Sierra Sun. His award-winning books, “Western Train Adventures: The Good, the Bad & the Ugly” and “Sierra Stories: Trues Tales of Tahoe, Vol. 1 & 2” are available at local bookstores. Mark, a Carnelian Bay resident, can be reached at mark@thestormking.com.