It may not seem like it during our region’s current drought, but the Truckee River is one of the most volatile waterways in California and Nevada, prone to flood about every nine years. The most recent significant flood event was in January 2006, so the statistical clock is ticking. Considering our current situation, a major flood on the Truckee doesn’t appear to be an immediate threat.
Floodwaters lick at River Ranch Restaurant in June 1969. | Courtesy Army Corps of Engineers
Virtually every major flood in the Sierra occurs during the winter months when warm sub-tropical storms bring prolonged heavy rain to the highest elevations. Not only does that torrential precipitation engorge our streams and rivers, it also melts the existing snowpack, which exacerbates hydrologic issues.
“The surge took out one bridge on the Truckee River
and then two more. Nothing could be done.”
In January 2016, I gave a presentation that included a review of the extreme New Year’s flood of 1997, which set a record for water flow released through the Tahoe dam. That flood wiped out many bridges between Truckee and Tahoe City and generated about $1 billion worth of damage on the total river system. Therefore, it came as a surprise when Olympic Valley’s Eric Poulsen later contacted me to say that he thought there was a bigger flow than that in June 1969.
As a weather historian knowledgeable about Tahoe’s biggest winters, I knew that the winter of 1968-69 was a blockbuster with more than 50 feet measured at Donner Pass. Persistent snow that year set many Nevada and Tahoe Sierra snowfall records. At Squaw Valley ski resort, 30-foot snow depths on the upper mountain enabled the resort to remain open for skiing until July 7. The winter of 1969 ranks No. 12 in total snowfall at Donner Pass, going back to 1879. I was aware of deep snow in 1969, but the idea of a record-setting discharge from Lake Tahoe in the month of June surprised me. Emergency water releases like that usually occur in winter during or shortly after the actual precipitation event.
How did a significant flood happen in June? In stark contrast to Lake Tahoe’s current water level at just 1 foot above its natural rim, during the winter of 1969 Big Blue was nearly full. A series of wet winters during the 1960s, combined with a federal water management policy that emphasized robust storage in Lake Tahoe, meant that water levels remained high those years. When nearly 40 inches of precipitation fell in just 90 days that winter (out of a seasonal total of more than 65 inches), there was little room to store the tremendous volume of runoff.
Claude Dukes, the federal water master, did his best to alleviate the danger of water piling up in Lake Tahoe. In the beginning of February, Dukes aggressively purged water from the lake, but storms hit incessantly that month and Big Blue’s level kept rising. By the end of February, Dukes was dumping huge amounts of water into the Truckee River. He opened most of the gates in the Tahoe dam, enabling a flow of about 1,750 cubic feet per second (cfs). In the following weeks, Dukes cut back Tahoe’s release rate to 1,200 cfs in order to reduce the risk for damage between the dam and the town of Truckee.
Even as June approached Dukes was still trying to balance between eliminating the potential for damage downstream versus breaching the legal maximum of Tahoe’s surface level at 6,229.1 feet, a limit that had been set by a federal court order in 1915. By June 9, the surface elevation of Lake Tahoe climbed to near 6,229 feet for the first time in 50 years since 1917. Complicating matters were record warm temperatures that accelerated snow melt. Dukes said, “Inflow hasn’t slacked off to the point I feel safe, but I think that I can control Tahoe’s elevation at 6,228.9 feet.”
It was an impossible balancing act that was doomed to fail. All 17 gates of the Tahoe dam were opened to just about maximum capacity, but the lake kept rising. On June 16, Tahoe City and the West Shore were struck by a thunderstorm that dumped nearly an inch of rain in just a few hours, part of an unusually wet spring pattern that complicated water-management issues. The downpour and resulting snowmelt surged into the lake pushing Big Blue to 6,229.03 feet, over the legal maximum. Claude Dukes had no choice and on June 20 he fully opened all 17 gates, sending 2,620 cfs downstream. It was the first time in the history of the dam that all floodgates had been opened to maximum.
The surge took out one bridge on the Truckee River and then two more. Nothing could be done. Dukes said, “We may keep the gates open for a week, I don’t know. It all depends on the weather. The object now is to hold the lake level, not lower it. We can lower it later when this crisis is over.” Over the next week, the water master got control of the situation, but the damage was done.
History repeated itself in January 1997 when high water forced Garry Stone, federal water master, to open all gates at the Tahoe dam, releasing a flow of 2,690 cfs. That epic surge beat the 1969 event by 70 cfs, the kind of extreme hydrologic event that will keep Tahoe’s federal water master up at night.
Tahoe historian Mark McLaughlin is a nationally published author and professional speaker. His award-winning books are available at local stores or at thestormking.com. You may reach him at [email protected] Check out his blog at tahoenuggets.com or read more at TheTahoeWeekly.com.